Manufacture of controlled rate dissolving materials

Abstract

A castable, moldable, or extrudable structure using a metallic base metal or base metal alloy. One or more insoluble additives are added to the metallic base metal or base metal alloy so that the grain boundaries of the castable, moldable, or extrudable structure includes a composition and morphology to achieve a specific galvanic corrosion rates partially or throughout the structure or along the grain boundaries of the structure. The insoluble additives can be used to enhance the mechanical properties of the structure, such as ductility and/or tensile strength. The insoluble particles generally have a submicron particle size. The final structure can be enhanced by heat treatment, as well as deformation processing such as extrusion, forging, or rolling, to further improve the strength of the final structure as compared to the non-enhanced structure.

Claims

1. A method for forming a dissolvable metal composite comprising: providing one or more metals used to form a base metal material, said base metal material includes one or more metals selected from the group consisting of magnesium, zinc, titanium, aluminum, and iron; providing a plurality of particles, said plurality of particles includes metal particles and/or metal alloy particles, at least one of said metal particles and/or at least one metal element in at least one of said metal alloys having a melting point that is greater than a melting point of said base metal material, said plurality of particles have a different galvanic potential from said base metal material; heating said base metal material until molten; mixing said molten base metal material and said plurality of particles to form a mixture and to cause said plurality of particles to disperse in said mixture; cooling said mixture to cast form said metal composite, a two or more particles of said plurality of particles not fully melted during said mixing step and during said cooling step; and, wherein said plurality of particles are disbursed in said metal composite to obtain a desired dissolution rate of said metal composite, at least 50% of said plurality of particles located in grain boundary layers of said metal composite, said plurality of particles selected and used in a quantity to obtain a composition and morphology of said grain boundary layers to obtain a galvanic corrosion rate along said grain boundary layers, said metal composite having a dissolution rate of at least 10 mg/cm.sup.2-hr in a 3% KCl solution at 90 C.

2. The method as defined in claim 1, wherein said step of mixing includes mixing using one or more processes selected from the group consisting of thixomolding, stir casting, mechanical agitation, electrowetting and ultrasonic dispersion.

3. The method as defined in claim 1, including the further step of extruding or deforming said metal composite to increase tensile strength, increase elongation to failure, or combinations thereof of said metal composite affecting a dissolution rate of said metal composite by no more than 10%.

4. The method as defined in claim 1, including the further step of extruding or deforming said metal composite to increase tensile strength, increase elongation to failure, or combinations thereof of said metal composite affecting a dissolution rate of said metal composite by no more than 10%.

5. The method as defined in claim 1, including the further step of forming said metal composite into a device for a) separating hydraulic fracturing systems and zones for oil and gas drilling, b) structural support or component isolation in oil and gas drilling and completion systems, or combinations thereof.

6. The method as defined in claim 1, wherein two or more particles of said plurality of particles having a melting point of greater than 700 C.

7. The method as defined in claim 1, wherein said base metal material includes a majority weight percent magnesium.

8. The method as defined in claim 1, wherein said plurality of particles including one or more materials selected from the group consisting of iron, graphite, beryllium, copper, titanium, nickel, carbon, zinc, tin, cadmium, lead, nickel, iron alloy, copper alloy, titanium alloy, zinc alloy, tin alloy, cadmium alloy, lead alloy, and nickel alloy.

9. The method as defined in claim 8, wherein said particles include one or more materials selected from the group consisting of iron, copper, titanium, and nickel.

10. The method as defined in claim 9, wherein said particles include one or more materials selected from the group consisting of copper and nickel.

11. The method as defined in claim 1, wherein said plurality of particles constitute 0.05-49.99 wt. % of said metal composite.

12. The method as defined in claim 1, wherein base metal material includes aluminum and zinc.

13. The method as defined in claim 1, wherein an average particle size of said plurality of particles is less than 1 m.

14. The method as defined in claim 1, wherein said plurality of particles includes first and second particle types, said first and second particle types having a different composition.

15. The method as defined in claim 1, wherein said plurality of particles have a selected size and shape to control a dissolution rate of said metal composite.

16. The method as defined in claim 1, wherein said plurality of particles have said galvanic potential that is more cathodic than said galvanic potential of said base metal material.

17. The method as defined in claim 1, wherein said plurality of particles have a solubility in said base metal material of less than 5%.

18. The method as defined in claim 1, wherein said plurality of particles have a surface area of about 0.001 m.sup.2/g-200 m.sup.2/g.

19. The method as defined in claim 1, wherein said plurality of particles include spherical particles of varying diameters.

20. The method as defined in claim 1, including the step of at least partially forming a ball or other component in a well drilling or completion operation from said metal composite.

21. The method as defined in claim 1, wherein said metal composite has a dissolution rate of at least 20 mg/cm.sup.2-hr. in a 3% KCl solution at 65 C.

22. The method as defined in claim 1, wherein said metal cast structure has a dissolution rate of at least 1 mg/cm.sup.2-hr. in a 3% KCl solution at 65 C.

23. The method as defined in claim 1, wherein said metal composite has a dissolution rate of at least 100 mg/cm.sup.2-hr. in a 3% KCl solution at 90 C.

24. A method for forming a dissolvable metal composite that includes a base metal material and a plurality of particles disbursed in said metal composite to obtain a desired dissolution rate of said metal composite comprising: providing said base metal material that is formed of a magnesium alloy; providing a plurality of particles, said plurality of particles include metal particles and/or metal alloy particles, at least one of said metal particles and/or at least one metal element in at least one of said metal alloys having a melting point that is greater than a melting point of said base metal material, said plurality of particles having a different galvanic potential from said base metal material, said plurality of particles including one or more materials selected from the group consisting of iron, copper, titanium, zinc, tin, cadmium, lead, beryllium, nickel, carbon, iron alloy, copper alloy, titanium alloy, zinc alloy, tin alloy, cadmium alloy, lead alloy, beryllium alloy, and nickel alloy, said plurality of particles constitute about 0.1-40 wt. % of said metal composite; heating said base metal material until molten; mixing said molten base metal material and said plurality of particles to form a mixture and to cause said plurality of particles to disperse in said mixture; cooling said mixture to cast form said metal composite, a two or more of said plurality of particles not fully melted during said mixing step and during said cooling step; and, wherein said plurality of particles are disbursed in said metal composite to obtain a desired dissolution rate of said metal composite, at least 50% of said plurality of particles located in grain boundary layers of said metal composite, said plurality of particles selected and used in a quantity to obtain a composition and morphology of said grain boundary layers to obtain a galvanic corrosion rate along said grain boundary layers, said metal composite having a dissolution rate of at least 10 mg/cm.sup.2-hr in a 3% KCl solution at 90 C.

25. The method as defined in claim 24, wherein said base metal material includes a majority weight percent magnesium.

26. The method as defined in claim 24, wherein said plurality of particles have a solubility in said base metal material of less than 5%.

27. The method as defined in claim 24, wherein said plurality of particles have a particle size of less than 1 m.

28. The method as defined in claim 24, wherein two or more particles of said plurality of particles have a melting point of greater than 700 C.

29. The method as defined in claim 24, wherein said plurality of particles include one or more materials selected from the group consisting of iron, beryllium, copper, titanium, nickel, and carbon.

30. The method as defined in claim 29, wherein said particles include one or more materials selected from the group consisting of iron, copper, titanium, and nickel.

31. The method as defined in claim 30, wherein said particles include one or more materials selected from the group consisting of copper and nickel.

32. The method as defined in claim 24, wherein said base metal material includes zinc.

33. The method as defined in claim 24, wherein said base metal material includes aluminum.

34. The method as defined in claim 24, wherein said base metal material is an alloy of magnesium, aluminum and zinc, an aluminum content in said base metal material is greater than a zinc content.

35. The method as defined in claim 24, wherein said metal composite has a dissolution rate of at least 20 mg/cm.sup.2-hr. in a 3% KCl solution at 65 C.

36. The method as defined in claim 24, wherein said metal composite has a dissolution rate of at least 1 mg/cm.sup.2-hr. in a 3% KCl solution at 65 C.

37. The method as defined in claim 24, wherein said metal composite has a dissolution rate of at least 100 mg/cm.sup.2-hr. in a 3% KCl solution at 90 C.

38. The method as defined in claim 24, including the step of at least partially forming a ball or other component in a well drilling or completion operation from said metal composite.

39. A method for forming a dissolvable metal composite that includes a base metal material and a plurality of particles disbursed in said metal composite to obtain a desired dissolution rate of said metal composite comprising: providing said base metal material that is formed of a magnesium alloy; providing a plurality of particles, said plurality of particles include metal particles and/or metal alloy particles, at least one of said metal particles and/or at least one metal element in at least one of said metal alloys having a melting point that is greater than a melting point of said base metal material, said plurality of particles having a different galvanic potential from said base metal material, said plurality of particles have a size that is less than about 1 m, said plurality of particles including one or more materials selected from the group consisting of iron, copper, titanium, zinc, tin, cadmium, beryllium, nickel, carbon, iron alloy, copper alloy, titanium alloy, zinc alloy, tin alloy, cadmium alloy, beryllium alloy, and nickel alloy, said plurality of particles constitute about 0.1-40 wt. % of said metal composite; heating said base metal material until molten; mixing said molten base metal material and said plurality of particles to form a mixture and to cause said plurality of particles to disperse in said mixture; cooling said mixture to cast form said metal composite, two or more of said plurality of particles not fully melted during said mixing step and during said cooling step; and, wherein said plurality of particles are disbursed in said metal composite to obtain a desired dissolution rate of said metal composite, at least 50% of said plurality of particles located in grain boundary layers of said metal composite, said plurality of particles selected and used in a quantity to obtain a composition and morphology of said grain boundary layers to obtain a galvanic corrosion rate along said grain boundary layers, said metal composite having a dissolution rate of at least 10 mg/cm.sup.2-hr in a 3% KCl solution at 90 C.

40. The method as defined in claim 39, wherein said base metal material includes a majority weight percent magnesium.

41. The method as defined in claim 39, wherein two or more of said plurality of particles have a melting point of greater than 700 C.

42. The method as defined in claim 39, wherein said plurality of particles include one or more materials selected from the group consisting of iron, beryllium, copper, titanium, nickel, and carbon.

43. The method as defined in claim 42, wherein said particles include one or more materials selected from the group consisting of iron, copper, titanium, and nickel.

44. The method as defined in claim 43, wherein said particles include one or more materials selected from the group consisting of copper and nickel.

45. The method as defined in claim 39, wherein said base metal material includes zinc.

46. The method as defined in claim 39, wherein said base metal material includes aluminum.

47. The method as defined in claim 39, wherein said base metal material is an alloy of magnesium, aluminum and zinc, an aluminum content in said base metal material is greater than a zinc content.

48. The method as defined in claim 39, wherein said metal composite has a dissolution rate of at least 20 mg/cm.sup.2-hr. in a 3% KCl solution at 65 C.

49. The method as defined in claim 39, wherein said metal composite has a dissolution rate of at least 1 mg/cm.sup.2-hr. in a 3% KCl solution at 65 C.

50. The method as defined in claim 39, wherein said metal composite has a dissolution rate of at least 100 mg/cm.sup.2-hr. in a 3% KCl solution at 90 C.

51. The method as defined in claim 39, including the step of at least partially forming a ball or other component in a well drilling or completion operation from said metal composite.

52. The method as defined in claim 39, wherein said plurality of particles having a solubility in said base metal material of less than 5%.

53. A method for forming a dissolvable metal composite for use as or in a tool for well drilling or a well completion operation comprising: providing a base metal, said base metal is selected from the group consisting of magnesium, aluminum, magnesium alloy and aluminum alloy; providing one or more secondary additives, said one or more secondary additives including one or more metals selected from the group consisting of iron, copper, titanium, zinc, tin, cadmium, beryllium, nickel, carbon, iron alloy, copper alloy, titanium alloy, zinc alloy, tin alloy, cadmium alloy, beryllium alloy, and nickel alloy, a plurality or said one or more secondary additives are elemental metals and/or metal alloys, at least one of said metals and/or at least one metal in at least one of said metal alloys has a melting point that is greater than said base metal; heating said base metal until molten; mixing said one or more secondary additives with said base metal to form a metal mixture; cooling said metal mixture to cast form said metal composite and to form grain boundary layers in said metal composite, said one or more secondary additives located in sufficient quantities in said grain boundary layers so as to obtain a composition and morphology of said grain boundary layers such that a galvanic corrosion rate along said grain boundary layers causes said metal composite to have a dissolution rate of at least 10 mg/cm.sup.2-hr. in a 3% KCl solution at 90 C., said one or more secondary additives located in said grain boundary layers having a different galvanic potential than said base metal, said base metal constitutes greater than 50 wt. % of said metal composite; and, forming said metal composite such that said tool is at least formed by said metal composite, said tool selected from the group consisting of a ball, sleeve, valve, and hydraulic actuating tool.

54. The method as defined in claim 53, wherein said base metal includes greater than 50 wt. % magnesium.

55. The method as defined in claim 53, wherein at least one of said one or more secondary additives have a melting point of greater than 700 C.

56. The method as defined in claim 53, wherein at least one of said one or more secondary additives is selected from the group consisting of iron, beryllium, copper, titanium, nickel, and carbon.

57. The method as defined in claim 56, wherein said particles include one or more materials selected from the group consisting of iron, copper, titanium, and nickel.

58. The method as defined in claim 57, wherein said particles include one or more materials selected from the group consisting of copper and nickel.

59. The method as defined in claim 53, wherein said metal composite has a dissolution rate of at least 20 mg/cm.sup.2-hr. in a 3% KCl solution at 65 C.

60. The method as defined in claim 53, wherein said metal composite has a dissolution rate of at least 1 mg/cm.sup.2-hr. in a 3% KCl solution at 65 C.

61. The method as defined in claim 53, wherein said metal composite has a dissolution rate of at least 100 mg/cm.sup.2-hr. in a 3% KCl solution at 90 C.

62. The method as defined in claim 53, further including the step of extruding, or casting or molding said metal composite prior to forming said tool.

63. A method for forming a dissolvable metal composite for use as or in a tool for well drilling or a well completion operation comprising: providing a base metal, said base metal is selected from the group consisting of magnesium, aluminum, magnesium alloy, and aluminum alloy; providing one or more secondary metals, said one or more secondary metals including one or more metals selected from the group consisting of iron, copper, titanium, and nickel, said one or more secondary metals are elemental metals and/or metal alloys, a particle size of said one or more secondary metals when added to said molten base metal is less than 1 m; heating said base metal until molten; mixing said one or more secondary metals with said base metal to form a metal mixture; cooling said metal mixture to form said metal composite and to form grain boundary layers in said metal composite, said one or more secondary metals located in said grain boundary layers so as to obtain a composition and morphology of said grain boundary layers such that a galvanic corrosion rate along said grain boundary layers causes said metal composite to have a dissolution rate of 100-325 mg/cm.sup.2-hr. in a 3% KCl solution at 90 C., said one or more secondary metals located in said grain boundary layers having a different galvanic potential than said base metal, said one or more secondary metals have a solubility in said base metal of less than 5%; and, forming said metal composite such that said tool is at least formed by said metal composite.

64. The method as defined in claim 63, further including the step of extruding, or casting or molding said metal composite prior to forming said tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a typical cast microstructure with grain boundaries (2) separating grains (1);

(2) FIG. 2 illustrates a detailed grain boundary (2) between two grains (1) wherein there is one non-soluble grain boundary addition (3) in a majority of grain boundary composition (4) wherein the grain boundary addition, the grain boundary composition, and the grain all have different galvanic potentials and different exposed surface areas; and,

(3) FIG. 3 illustrates a detailed grain boundary (2) between two grains (1) wherein there are two non-soluble grain boundary additions (3 and 5) in a majority of grain boundary composition (4) wherein the grain boundary additions, the grain boundary composition, and the grain all have different galvanic potentials and different exposed surface areas.

DETAILED DESCRIPTION OF THE INVENTION

(4) Referring now to the figures wherein the showings illustrate non-limiting embodiments of the present invention, the present invention is directed to a metal cast structure that includes insoluble particles dispersed in the cast metal material. The metal cast structure of the present invention can be used as a dissolvable, degradable and/or reactive structure in oil drilling. For example, the metal cast structure can be used to form a frack ball or other structure (e.g., sleeves, valves, hydraulic actuating tooling and the like, etc.) in a well drilling or completion operation. Although the metal cast structure has advantageous applications in the drilling or completion operation field of use, it will be appreciated that the metal cast structure can be used in any other field of use wherein it is desirable to form a structure that is controllably dissolvable, degradable and/or reactive.

(5) The metal cast structure includes a base metal or base metal alloy having at least one insoluble phase in discrete particle form that is disbursed in the base metal or base metal alloy. The metal cast structure is generally produced by casting. The discrete insoluble particles have a different galvanic potential from the base metal or base metal alloy. The discrete insoluble particles are generally uniformly dispersed through the base metal or base metal alloy using techniques such as, but not limited to, thixomolding, stir casting, mechanical agitation, electrowetting, ultrasonic dispersion and/or combinations of these methods; however, this is not required. In one non-limiting process, the insoluble particles are uniformly dispersed through the base metal or base metal alloy using ultrasonic dispersion. Due to the insolubility and difference in atomic structure in the melted base metal or base metal alloy and the insoluble particles, the insoluble particles will be pushed to the grain boundary of the mixture of insoluble particles and the melted base metal or base metal alloy as the mixture cools and hardens during casting solidification. Because the insoluble particles will generally be pushed to the grain boundary, such feature makes it possible to engineer/customize grain boundaries in the metal cast structure to control the dissolution rate of the metal cast structure. This feature can be also used to engineer/customize grain boundaries in the metal cast structure through traditional deformation processing (e.g., extrusion, tempering, heat treatment, etc.) to increase tensile strength, elongation to failure, and other properties in the metal cast structure that were not achievable in cast metal structures that were absent insoluble particle additions. Because the amount or content of insoluble particles in the grain boundary is generally constant in the metal cast structure, and the grain boundary to grain surface area is also generally constant in the metal cast structure even after and optional deformation processing and/or heat treatment of the metal cast structure, the corrosion rate of the metal cast structure remains very similar or constant throughout the corrosion of the complete metal cast structure.

(6) The metal cast structure can be designed to corrode at the grains in the metal cast structure, at the grain boundaries of the metal cast structure, and/or the location of the insoluble particle additions in the metal cast structure depending on selecting where the insoluble particle additions fall on the galvanic chart. For example, if it is desired to promote galvanic corrosion only along the grain boundaries (1) as illustrated in FIGS. 1-3, a metal cast structure can be selected such that one galvanic potential exists in the base metal or base metal alloy where its major grain boundary alloy composition (4) will be more anodic as compared to the matrix grains (i.e., grains that form in the casted base metal or base metal alloy) located in the major grain boundary, and then an insoluble particle addition (3) will be selected which is more cathodic as compared to the major grain boundary alloy composition. This combination will cause corrosion of the material along the grain boundaries, thereby removing the more anodic major grain boundary alloy (4) at a rate proportional to the exposed surface area of the cathodic particle additions (3) to the anodic major grain boundary alloy (4). The current flowing in the grain boundary can be calculated by testing zero resistance current of the cathode to the anode in a solution at a desired solution temperature and pressure that includes the metal cast structure. Corrosion of the metal cast structure will be generally proportional to current density/unit area of the most anodic component in the grain boundary and/or grains until that component is removed. If electrical conductivity remains between the remaining components in the grain boundary, the next most anodic component in the grain boundary and/or grains will next be removed at a desired temperature and pressure.

(7) Galvanic corrosion in the grains (2) can be promoted in the metal cast structure by selecting a base metal or base metal alloy that has at one galvanic potential in the operating solution of choice (e.g., fracking solution, brine solution, etc.) where its major grain boundary alloy composition (4) is more cathodic as compared to the matrix grains (i.e., grains that form in the casted base metal or base metal alloy), and an insoluble particle addition (3) is selected that is more cathodic as compared to the major grain boundary alloy composition and the base metal or base metal alloy. This combination will result in the corrosion of the metal cast structure through the grains by removing the more anodic grain (2) composition at a rate proportional to the exposed surface area of the cathodic non-soluble particle additions (3) to the anodic major grain boundary alloy (4). The current flowing in the metal cast structure can be calculated by testing zero resistance current of the cathode to the anode in a solution at a desired solution temperature and pressure that includes the metal cast structure. Corrosion of the metal cast structure will be generally proportional to current density/unit area of the most anodic component in the grain boundary and/or grains until that component is removed. If electrical conductivity remains between the remaining components in the grain boundary, the next most anodic component in the grain boundary and/or grains will next be removed at a desired temperature and pressure.

(8) If a slower corrosion rate of the metal cast structure is desired, two or more insoluble particle additions can be added to the metal cast structure to be deposited at the grain boundary as illustrated in FIG. 3. If the second insoluble particle (5) is selected to be the most anodic in the metal cast structure, the second insoluble particle will first be corroded, thereby generally protecting the remaining components of the metal cast structure based on the exposed surface area and galvanic potential difference between second insoluble particle and the surface area and galvanic potential of the most cathodic system component. When the exposed surface area of the second insoluble particle (5) is removed from the system, the system reverts to the two previous embodiments described above until more particles of second insoluble particle (5) are exposed. This arrangement creates a mechanism to retard corrosion rate with minor additions of the second insoluble particle component.

(9) The rate of corrosion in the metal cast structure can also be controlled by the surface area of the insoluble particle. As such the particle size, particle morphology and particle porosity of the insoluble particles can be used to affect the rate of corrosion of the metal cast structure. The insoluble particles in the metal cast structure can optionally have a surface area of 0.001 m.sup.2/g-200 m.sup.2/g (and all values and ranges therebetween). The insoluble particles in the metal cast structure optionally are or include non-spherical particles. The insoluble particles in the metal cast structure optionally are or include nanotubes and/or nanowires. The non-spherical insoluble particles can optionally be used at the same volume and/or weight fraction to increase cathode particle surface area to control corrosion rates without changing composition. The insoluble particles in the metal cast structure optionally are or include spherical particles. The spherical particles (when used) can have the same or varying diameters. Such particles are optionally used at the same volume and/or weight fraction to increase cathode particle surface area to control corrosion rates without changing composition.

(10) The major grain boundary composition of the metal cast structure metal cast structure can include magnesium, zinc, titanium, aluminum, iron, or any combination or alloys thereof. The added insoluble particle component that has a more anodic potential than the major grain boundary composition can include, but is not limited to, beryllium, magnesium, aluminum, zinc, cadmium, iron, tin, copper, and any combinations and/or alloys thereof. The added insoluble particle component that has a more cathodic potential than the major grain boundary composition can include, but is not limited to, iron, copper, titanium, zinc, tin, cadmium lead, nickel, carbon, boron carbide, and any combinations and/or alloys thereof. The grain boundary layer can include an added insoluble particle component that is more cathodic as compared to the major grain boundary composition. The composition of the grain boundary layer can optionally include an added component that is more anodic as compared to the major component of the grain boundary composition. The composition of the grain boundary layer can optionally include an added insoluble particle component that is more cathodic as compared to the major component of the grain boundary composition and the major component of the grain boundary composition can be more anodic than the grain composition. The cathodic components or anodic components can be compatible with the base metal or metal alloy (e.g., matrix material) in that the cathodic components or anodic components can have solubility limits and/or do not form compounds.

(11) The insoluble particle component (anodic component or cathodic component) that is added to the metal cast structure generally has a solubility in the grain boundary composition of less than about 5% (e.g., 0.01-4.99% and all values and ranges therebetween), typically less than about 1%, and more typically less than about 0.5%. The composition of the cathodic or anodic insoluble particle components in the grain boundary can be compatible with the major grain boundary material in that the cathodic components or anodic components can have solubility limits and/or do not form compounds.

(12) The strength of the metal cast structure can optionally be increased using deformation processing and a change dissolution rate of the metal cast structure of less than about 20% (e.g., 0.01-19.99% and all values and ranges therebetween), typically less than about 10%, and more typically less than about 5%.

(13) The ductility of the metal cast structure can optionally be increased using insoluble nanoparticle cathodic additions. In one non-limiting specific embodiment, the metal cast structure includes a magnesium and/or magnesium alloy as the base metal or base metal alloy, and more insoluble nanoparticle cathodic additions include carbon and/or iron. In another non-limiting specific embodiment, the metal cast structure includes aluminum and/or aluminum alloy as the base metal or base metal alloy, and more anodic galvanic potential insoluble nanoparticles include magnesium or magnesium alloy, and high galvanic potential insoluble nanoparticle cathodic additions include carbon, iron and/or iron alloy. In still another non-limiting specific embodiment, the metal cast structure includes aluminum, aluminum alloy, magnesium and/or magnesium alloy as the base metal or base metal alloy, and the more anodic galvanic potential insoluble nanoparticles include magnesium and/or magnesium alloy, and the more insoluble nanoparticle cathodic additions include titanium. In yet another non-limiting specific embodiment, the metal cast structure includes aluminum and/or aluminum alloy as the base metal or base metal alloy, and the more anodic galvanic potential insoluble nanoparticles include magnesium and/or magnesium alloy, and the high galvanic potential insoluble nanoparticle cathodic additions include iron and/or iron alloy. In still yet another non-limiting specific embodiment, the metal cast structure includes aluminum and/or aluminum alloy as the base metal or base metal alloy, and the more anodic galvanic potential insoluble nanoparticles include magnesium and/or magnesium alloy, and the high galvanic potential insoluble nanoparticle cathodic additions include titanium. In another non-limiting specific embodiment, the metal cast structure includes magnesium, aluminum, magnesium alloys and/or aluminum alloy as the base metal or base metal alloy, and the high galvanic potential insoluble nanoparticle cathodic additions include titanium.

(14) The metal cast structure can optionally include chopped fibers. These additions to the metal cast structure can be used to improve toughness of the metal cast structure.

(15) The metal cast structure can have improved tensile strength and/or elongation due to heat treatment without significantly affecting the dissolution rate of the metal cast structure.

(16) The metal cast structure can have improved tensile strength and/or elongation by extrusion and/or another deformation process for grain refinement without significantly affecting the dissolution rate of the metal cast structure. In such a process, the dissolution rate change can be less than about 10% (e.g., 0-10% and all values and ranges therebetween), typically less than about 5%, and more typically less than about 1%.

(17) Particle reinforcement in the metal cast structure can optionally be used to improve the mechanical properties of the metal cast structure and/or to act as part of the galvanic couple.

(18) The insoluble particles in the metal cast structure can optionally be used as a grain refiner, as a stiffening phase to the base metal or metal alloy (e.g., matrix material), and/or to increase the strength of the metal cast structure.

(19) The insoluble particles in the metal cast structure are generally less than about 1 m in size (e.g., 0.00001-0.999 m and all values and ranges therebetween), typically less than about 0.5 m, more typically less than about 0.1 m, and typically less than about 0.05 m, still more typically less than 0.005 m, and yet still more typically no greater than 0.001 m (nanoparticle size).

(20) The total content of the insoluble particles in the metal cast structure is generally about 0.01-70 wt. % (and all values and ranges therebetween), typically about 0.05-49.99 wt. %, more typically about 0.1-40 wt %, still more typically about 0.1-30 wt. %, and even more typically about 0.5-20 wt. %. When more than one type of insoluble particle is added in the metal cast structure, the content of the different types of insoluble particles can be the same or different. When more than one type of insoluble particle is added in the metal cast structure, the shape of the different types of insoluble particles can be the same or different. When more than one type of insoluble particle is added in the metal cast structure, the size of the different types of insoluble particles can be the same or different.

(21) The insoluble particles can optionally be dispersed throughout the metal cast structure using ultrasonic means, by electrowetting of the insoluble particles, and/or by mechanical agitation.

(22) The metal cast structure can optionally be used to form all or part of a device for use in hydraulic fracturing systems and zones for oil and gas drilling, wherein the device has a designed dissolving rate. The metal cast structure can optionally be used to form all or part of a device for structural support or component isolation in oil and gas drilling and completion systems, wherein the device has a designed dissolving rate.

Example 1

(23) An AZ91D magnesium alloy having 9 wt. % aluminum, 1 wt. % zinc and 90 wt. % magnesium was melted to above 700 C. About 16 wt. % of 75 um iron particles were added to the melt and dispersed. The melt was cast into a steel mold. The iron particles did not fully melt during the mixing and casting processes. The cast material exhibited a tensile strength of about 26 ksi, and an elongation of about 3%. The cast material dissolved at a rate of about 2.5 mg/cm.sup.2-min in a 3% KCl solution at 20 C. The material dissolved at a rate of 60 mg/cm.sup.2-hr in a 3% KCl solution at 65 C. The material dissolved at a rate of 325 mg/cm.sup.2-hr. in a 3% KCl solution at 90 C. The dissolving rate of metal cast structure for each these test was generally constant. The iron particles were less than 1 m, but were not nanoparticles. However, the iron particles could be nanoparticles, and such addition would change the dissolving rate of metal cast structure.

Example 2

(24) An AZ91D magnesium alloy having 9 wt. % aluminum, 1 wt. % zinc and 90 wt. % magnesium was melted to above 700 C. About 2 wt. % 75 um iron particles were added to the melt and dispersed. The melt was cast into steel molds. The iron particles did not fully melt during the mixing and casting processes. The material exhibited a tensile strength of 26 ksi, and an elongation of 4%. The material dissolved at a rate of 0.2 mg/cm.sup.2-min in a 3% KCl solution at 20 C. The material dissolved at a rate of 1 mg/cm.sup.2-hr in a 3% KCl solution at 65 C. The material dissolved at a rate of 10 mg/cm.sup.2-hr in a 3% KCl solution at 90 C. The dissolving rate of metal cast structure for each these test was generally constant. The iron particles were less than 1 m, but were not nanoparticles. However, the iron particles could be nanoparticles, and such addition would change the dissolving rate of metal cast structure.

Example 3

(25) An AZ91D magnesium alloy having 9 wt. % aluminum, 1 wt. % zinc and 90 wt. % magnesium was melted to above 700 C. About 2 wt. % nano iron particles and about 2 wt. % nano graphite particles were added to the composite using ultrasonic mixing. The melt was cast into steel molds. The iron particles and graphite particles did not fully melt during the mixing and casting processes. The material dissolved at a rate of 2 mg/cm.sup.2-min in a 3% KCl solution at 20 C. The material dissolved at a rate of 20 mg/cm.sup.2-hr in a 3% KCl solution at 65 C. The material dissolved at a rate of 100 mg/cm.sup.2-hr in a 3% KCl solution at 90 C. The dissolving rate of metal cast structure for each these test was generally constant.

Example 4

(26) The composite in Example 1 was subjected to extrusion with an 11:1 reduction area. The extruded metal cast structure exhibited a tensile strength of 38 ksi, and an elongation to failure of 12%. The extruded metal cast structure dissolved at a rate of 2 mg/cm.sup.2-min in a 3% KCl solution at 20 C. The extruded metal cast structure dissolved at a rate of 301 mg/cm.sup.2-min in a 3% KCl solution at 20 C. The extruded metal cast structure exhibit an improvement of 58% tensile strength and an improvement of 166% elongation with less than 10% change in dissolution rate as compared to the non-extruded metal cast structure.

(27) It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the constructions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. The invention has been described with reference to preferred and alternate embodiments. Modifications and alterations will become apparent to those skilled in the art upon reading and understanding the detailed discussion of the invention provided herein. This invention is intended to include all such modifications and alterations insofar as they come within the scope of the present invention. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention, which, as a matter of language, might be said to fall there between. The invention has been described with reference to the preferred embodiments. These and other modifications of the preferred embodiments as well as other embodiments of the invention will be obvious from the disclosure herein, whereby the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims.