Galvanically-active in situ formed particles for controlled rate dissolving tools

Abstract

A tastable, moldable, and/or extrudable structure using a metallic primary alloy. One or more additives are added to the metallic primary alloy so that in situ galvanically-active reinforcement particles are formed in the melt or on cooling from the melt. The composite contains an optimal composition and morphology to achieve a specific galvanic corrosion rate in the entire composite. The in situ formed galvanically-active particles can be used to enhance mechanical properties of the composite, such as ductility and/or tensile strength. The final casting can also be enhanced by heat treatment, as well as deformation processing such as extrusion, forging, or rolling, to further improve the strength of the final composite over the as-cast material.

Claims

1. A method of controlling the dissolution properties of a magnesium composite comprising: heating a magnesium material above a solidus temperature of magnesium, said magnesium material including magnesium and one or more metals selected from the group consisting of aluminum, boron, bismuth, zinc, zirconium, and manganese; adding first and second additives to said magnesium material while said magnesium material is above said solidus temperature of magnesium to form a magnesium mixture, said first additive including one or more metals selected from the group consisting of nickel, cobalt, copper, lead, antimony, indium, gold, and gallium, said second additive including one or more metals selected from the group consisting of calcium, strontium, barium, potassium, sodium, lithium, cesium, yttrium, lanthanum, samarium, europium, gadolinium, terbium, dysprosium, holmium, and ytterbium; dispersing said first and second additives in said magnesium mixture while said magnesium mixture is above said solidus temperature of magnesium; and, cooling said magnesium mixture to form said magnesium composite, said magnesium composite including in situ precipitation of galvanically-active intermetallic phases, said magnesium composite includes 0.05-10 wt. % aluminum when aluminum is included in said magnesium composite, a combined content of said first and second additives constituting about 0.05-45 wt. % of said magnesium composite; and, wherein said magnesium composite has a dissolution rate of at least 5 mg/cm.sup.2-hr. in 3% KCl at 90° C.

2. The method as defined in claim 1, wherein said magnesium material is heated during said step of heating to a temperature that is less than said melting point temperature of one of said first and/or second additives.

3. The method as defined in claim 1, wherein said first additive includes one or more metals selected from the group consisting of copper, nickel, cobalt, bismuth, silver, and gallium, and said second additive includes one or more metals selected from the group consisting of calcium, strontium, and barium.

4. The method as defined in claim 1, wherein said magnesium composite includes greater than 50 wt. %.

5. The method as defined in claim 1, including the step of forming said magnesium composite into a final shape or near net shape by a) sand casting, permanent mold casting, investment casting, shell molding, or pressureless casting technique at a temperature above 730° C., 2) using either pressure addition or elevated pouring temperatures above 710° C., or 3) subjecting said magnesium composite to pressures of 2000-20,000 psi through use of squeeze casting, thixomolding, or pressure die casting techniques.

6. The method as defined in claim 1, wherein said magnesium composite has a hardness above 14 Rockwell Harness B.

7. The method as defined in claim 1, wherein said magnesium composite includes about 0.05-35 wt. % nickel.

8. The method as defined in claim 1, wherein said magnesium composite includes about 0.05-35 wt. % copper.

9. The method as defined in claim 1, wherein said magnesium composite includes about 0.05-35 wt. % antimony.

10. The method as defined in claim 1, wherein said magnesium composite includes about 0.05-35 wt. % gallium.

11. The method as defined in claim 1, wherein said magnesium composite includes about 0.05-35 wt. % tin.

12. The method as defined in claim 1, wherein said magnesium composite includes about 0.05-35 wt. % bismuth.

13. The method as defined in claim 1, wherein said magnesium composite includes about 0.05-35 wt. % calcium.

14. A method of controlling the dissolution properties of a magnesium composite comprising: heating magnesium material above a solidus temperature of magnesium, said magnesium material including greater than 50 wt. % magnesium and one or more metals selected from the group consisting of aluminum, boron, bismuth, zinc, zirconium, and manganese; adding additive material to said magnesium material while said magnesium material is above said solidus temperature of magnesium to form a magnesium mixture, said additive material including first additive and second additive, said first additive including one or more metals selected from the group consisting of nickel, cobalt, copper, bismuth, silver, and gallium, said second additive including one or more metals selected from the group consisting of calcium, strontium, and barium; dispersing said additive material in said magnesium mixture while said magnesium mixture is above said solidus temperature of magnesium; and, cooling said magnesium mixture to form said magnesium composite, said magnesium composite including in situ precipitation of galvanically-active intermetallic phases, said magnesium composite including greater than 50 wt. % magnesium and 0.05-10 wt. % aluminum when aluminum is included in said magnesium composite, said additive material constituting about 0.05-45 wt. % of said magnesium composite, and wherein said magnesium composite has a dissolution rate of at least 5 mg/cm.sup.2-hr. in 3% KCl at 90° C.

15. The method as defined in claim 14, wherein said first additive includes one or more metals selected from the group consisting of copper, nickel, cobalt, and gallium.

16. The method as defined in claim 14, wherein said second additive includes calcium.

17. The method as defined in claim 15, wherein said second additive includes calcium.

18. The method as defined in claim 14, wherein said magnesium composite includes at least 85 wt. % magnesium.

19. The method as defined in claim 17, wherein said magnesium composite includes at least 85 wt. % magnesium.

20. The method as defined in claim 14, including the step of forming said magnesium composite into a final shape or near net shape by a) sand casting, permanent mold casting, investment casting, shell molding, or pressureless casting technique at a temperature above 730° C., 2) using either pressure addition or elevated pouring temperatures above 710° C., or 3) subjecting said magnesium composite to pressures of 2000-20,000 psi through use of squeeze casting, thixomolding, or pressure die casting techniques.

21. The method as defined in claim 19, including the step of forming said magnesium composite into a final shape or near net shape by a) sand casting, permanent mold casting, investment casting, shell molding, or pressureless casting technique at a temperature above 730° C., 2) using either pressure addition or elevated pouring temperatures above 710° C., or 3) subjecting said magnesium composite to pressures of 2000-20,000 psi through use of squeeze casting, thixomolding, or pressure die casting techniques.

22. The method as defined in claim 20, wherein said final shape or near net shape is in the form of a valve, a valve component, a plug, a frac ball, a sleeve, a hydraulic actuating tool, or a mandrel.

23. The method as defined in claim 21, wherein said final shape or near net shape is in the form of a valve, a valve component, a plug, a frac ball, a sleeve, a hydraulic actuating tool, or a mandrel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1-3 show a typical cast microstructure with galvanically-active in situ formed intermetallic phase wetted to the magnesium matrix; and,

(2) FIG. 4 shows a typical phase diagram to create in situ formed particles of an intermetallic Mg.sub.x(M), Mg(M.sub.x) and/or unalloyed M and/or M alloyed with another M where M is any element on the periodic table or any compound in a magnesium matrix and wherein M has a electronegativity that is greater than 1.5 or an electronegativity that is less than 1.25.

DETAILED DESCRIPTION OF THE INVENTION

(3) Referring now to the figures wherein the showings illustrate non-limiting embodiments of the present invention, the present invention is directed to a magnesium composite that includes one or more additives dispersed in the magnesium composite. The magnesium composite of the present invention can be used as a dissolvable, degradable and/or reactive structure in oil drilling. For example, the magnesium composite can be used to form a frac ball or other structure (e.g., sleeves, valves, hydraulic actuating tooling and the like, etc.) in a well drilling or completion operation. Although the magnesium composite has advantageous applications in the drilling or completion operation field of use, it will be appreciated that the magnesium composite 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.

(4) The present invention is directed to a novel magnesium composite that can be used to form a castable, moldable, or extrudable component. The magnesium composite includes at least 50 wt. % magnesium. Generally, the magnesium composite includes over 50 wt. % magnesium and less than about 99.5 wt. % magnesium and all values and ranges therebetween. One or more additives are added to a magnesium or magnesium alloy to form the novel magnesium composite of the present invention. The one or more additives can be selected and used in quantities so that galvanically-active intermetallic or insoluble precipitates form in the magnesium or magnesium alloy while the magnesium or magnesium alloy is in a molten state and/or during the cooling of the melt; however, this is not required. The one or more additives are added to the molten magnesium or magnesium alloy at a temperature that is typically less than the melting point of the one or more additives; however, this is not required. During the process of mixing the one or more additives in the molten magnesium or magnesium alloy, the one or more additives are not caused to fully melt in the molten magnesium or magnesium alloy; however, this is not required. For additives that partially or fully melt in the molten magnesium or molten magnesium alloy, these additives form alloys with magnesium and/or other additives in the melt, thereby resulting in the precipitation of such formed alloys during the cooling of the molten magnesium or molten magnesium alloy to form the galvanically-active phases in the magnesium composite. After the mixing process is completed, the molten magnesium or magnesium alloy and the one or more additives that are mixed in the molten magnesium or magnesium alloy are cooled to form a solid magnesium component that includes particles in the magnesium composite. Such a formation of particles in the melt is called in situ particle formation as illustrated in FIGS. 1-3. Such a process can be used to achieve a specific galvanic corrosion rate in the entire magnesium composite and/or along the grain boundaries of the magnesium composite. This feature results in the ability to control where the galvanically-active phases are located in the final casting, as well as the surface area ratio of the in situ phase to the matrix phase, which enables the use of lower cathode phase loadings as compared to a powder metallurgical or alloyed composite to achieve the same dissolution rates. The in situ formed galvanic additives can be used to enhance mechanical properties of the magnesium composite such as ductility, tensile strength, and/or shear strength. The final magnesium composite can also be enhanced by heat treatment as well as deformation processing (such as extrusion, forging, or rolling) to further improve the strength of the final composite over the as-cast material; however, this is not required. The deformation processing can be used to achieve strengthening of the magnesium composite by reducing the grain size of the magnesium composite. Further enhancements, such as traditional alloy heat treatments (such as solutionizing, aging and/or cold working) can be used to enable control of dissolution rates though precipitation of more or less galvanically-active phases within the alloy microstructure while improving mechanical properties; however, this is not required. Because galvanic corrosion is driven by both the electrode potential between the anode and cathode phase, as well as the exposed surface area of the two phases, the rate of corrosion can also be controlled through adjustment of the in situ formed particles size, while not increasing or decreasing the volume or weight fraction of the addition, and/or by changing the volume/weight fraction without changing the particle size. Achievement of in situ particle size control can be achieved by mechanical agitation of the melt, ultrasonic processing of the melt, controlling cooling rates, and/or by performing heat treatments. In situ particle size can also or alternatively be modified by secondary processing such as rolling, forging, extrusion and/or other deformation techniques. A smaller particle size can be used to increase the dissolution rate of the magnesium composite. An increase in the weight percent of the in situ formed particles or phases in the magnesium composite can also or alternatively be used to increase the dissolution rate of the magnesium composite. A phase diagram for forming in situ formed particles or phases in the magnesium composite is illustrated in FIG. 4.

(5) In accordance with the present invention, a novel magnesium composite is produced by casting a magnesium metal or magnesium alloy with at least one component to form a galvanically-active phase with another component in the chemistry that forms a discrete phase that is insoluble at the use temperature of the dissolvable component. The in situ formed particles and phases have a different galvanic potential from the remaining magnesium metal or magnesium alloy. The in situ formed particles or phases are uniformly dispersed through the matrix metal or metal alloy using techniques such as thixomolding, stir casting, mechanical agitation, chemical agitation, electrowetting, ultrasonic dispersion, and/or combinations of these methods. Due to the particles being formed in situ to the melt, such particles generally have excellent wetting to the matrix phase and can be found at grain boundaries or as continuous dendritic phases throughout the component depending on alloy composition and the phase diagram. Because the alloys form galvanic intermetallic particles where the intermetallic phase is insoluble to the matrix at use temperatures, once the material is below the solidus temperature, no further dispersing or size control is necessary in the component. This feature also allows for further grain refinement of the final alloy through traditional deformation processing to increase tensile strength, elongation to failure, and other properties in the alloy system that are not achievable without the use of insoluble particle additions. Because the ratio of in situ formed phases in the material is generally constant and the grain boundary to grain surface area is typically consistent even after deformation processing and heat treatment of the composite, the corrosion rate of such composites remains very similar after mechanical processing.

Example 1

(6) An AZ91D magnesium alloy having 9 wt. % aluminum, 1 wt. % zinc and 90 wt. % magnesium was melted to above 800° C. and at least 200° C. below the melting point of nickel. About 7 wt. % of nickel was added to the melt and dispersed. The melt was cast into a steel mold. The cast material exhibited a tensile strength of about 14 ksi, an elongation of about 3%, and shear strength of 11 ksi. The cast material dissolved at a rate of about 75 mg/cm.sup.2-min in a 3% KCl solution at 90° C. The material dissolved at a rate of 1 mg/cm.sup.2-hr in a 3% KCl solution at 21° C. The material dissolved at a rate of 325 mg/cm.sup.2-hr. in a 3% KCl solution at 90° C.

Example 2

(7) The composite in Example 1 was subjected to extrusion with an 11:1 reduction area. The material exhibited a tensile yield strength of 45 ksi, an Ultimate tensile strength of 50 ksi and an elongation to failure of 8%. The material has a dissolve rate of 0.8 mg/cm.sup.2-min. in a 3% KCl solution at 20° C. The material dissolved at a rate of 100 mg/cm.sup.2-hr. in a 3% KCl solution at 90° C.

Example 3

(8) The alloy in Example 2 was subjected to an artificial T5 age treatment of 16 hours from 100-200° C. The alloy exhibited a tensile strength of 48 ksi and elongation to failure of 5% and a shear strength of 25 ksi. The material dissolved at a rate of 110 mg/cm.sup.2-hr. in 3% KCl solution at 90° C. and 1 mg/cm.sup.2-hr. in 3% KCl solution at 20° C.

Example 4

(9) The alloy in Example 1 was subjected to a solutionizing treatment T4 of 18 hours from 400° C.-500° C. and then an artificial T6 aging process of 16 hours from 100-200 C. The alloy exhibited a tensile strength of 34 ksi and elongation to failure of 11% and a shear strength of 18 Ksi. The material dissolved at a rate of 84 mg/cm.sup.2-hr. in 3% KCl solution at 90° C. and 0.8 mg/cm.sup.2-hr. in 3% KCl solution at 20° C.

Example 5

(10) An AZ91D magnesium alloy having 9 wt. % aluminum, 1 wt. % zinc, and 90 wt. % magnesium was melted to above 800° C. and at least 200° C. below the melting point of copper. About 10 wt. % of copper alloyed to the melt and dispersed. The melt was cast into a steel mold. The cast material exhibited a tensile yield strength of about 14 ksi, an elongation of about 3%, and shear strength of 11 ksi. The cast material dissolved at a rate of about 50 mg/cm.sup.2-hr. in a 3% KCl solution at 90° C. The material dissolved at a rate of 0.6 mg/cm.sup.2-hr. in a 3% KCl solution at 21° C.

Example 6

(11) The alloy in Example 5 was subjected to an artificial T5 aging process of 16 hours from 100-200° C. The alloy exhibited a tensile strength of 50 ksi and elongation to failure of 5% and a shear strength of 25 ksi. The material dissolved at a rate of 40 mg/cm′-hr. in 3% KCl solution at 90° C. and 0.5 mg/cm.sup.2-hr. in 3% KCl solution at 20° C.

Example 7

(12) 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 μm iron particles were added to the melt and dispersed. The melt was cast into a steel mold. 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.

Example 8

(13) 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 μm iron particles were added to the melt and dispersed. The melt was cast into steel molds. 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.

Example 9

(14) 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 material dissolved at a rate of 2 mg/cm2-min in a 3% KCl solution at 20° C. The material dissolved at a rate of 20 mg/cm2-hr in a 3% KCl solution at 65° C. The material dissolved at a rate of 100 mg/cm2-hr in a 3%© KCl solution at 90° C.

Example 10

(15) The composite in Example 7 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/cm2-min in a 3%© KCl solution at 20° C. The extruded metal cast structure dissolved at a rate of 301 mg/cm2-min in a 3% KCl solution at 90° C. The extruded metal cast structure exhibited 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.

Example 11

(16) Pure magnesium was melted to above 650° C. and below 750° C. About 7 wt. % of antimony was dispersed in the molten magnesium. The melt was cast into a steel mold. The cast material dissolved at a rate of about 20.09 mg/cm.sup.2-hr in a 3% KCl solution at 90° C.

Example 12

(17) Pure magnesium was melted to above 650° C. and below 750° C. About 5 wt % of gallium was dispersed in the molten magnesium. The melt was cast into a steel mold. The cast material dissolved at a rate of about 0.93 mg/cm.sup.2-hr in a 3% KCl solution at 90° C.

Example 13

(18) Pure magnesium was melted to above 650° C. and below 750° C. About 13 wt. % of tin was dispersed in the molten magnesium. The melt was cast into a steel mold. The cast material dissolved at a rate of about 0.02 mg/cm.sup.2-hr in a 3% KCl solution at 90° C.

Example 14

(19) A magnesium alloy that included 9 wt. % aluminum, 0.7 wt. % zinc, 0.3 wt. % nickel, 0.2 wt. % manganese, and the balance magnesium was heated to 157° C. (315° F.) under an SF.sub.6—CO.sub.2 cover gas blend to provide a protective dry atmosphere for the magnesium alloy. The magnesium alloy was then heated to 730° C. to melt the magnesium alloy and calcium was then added into the molten magnesium alloy in an amount that the calcium constituted 2 wt. % of the mixture. The mixture of molten magnesium alloy and calcium was agitated to adequately disperse the calcium within the molten magnesium alloy. The mixture was then poured into a preheated and protective gas-filled steel mold and naturally cooled to form a cast part that was a 9″×32″ billet. The billet was subsequently preheated to ˜350° C. and extruded into a solid and tubular extrusion profile. The extrusions were run at 12 and 7 inches/minute respectively, which is 2×-3× faster than the maximum speed the same alloy achieved without calcium alloying. It was determined that once the molten mixture was cast into a steel mold, the molten surface of the mixture in the mold did not require an additional cover gas or flux protection during solidification. This can be compared to the same magnesium-aluminum alloy without calcium that requires either an additional cover gas or flux during solidification to prevent burning.

(20) The effect of the calcium on the corrosion rate of a magnesium-aluminum-nickel alloy was determined. Since magnesium already has a high galvanic potential with nickel, the magnesium alloy corrodes rapidly in an electrolytic solution such as a potassium chloride brine. The KCl brine was a 3% solution heated to 90° C. (194° F.). The corrosion rate was compared by submerging 1″×0.6″ samples of the magnesium alloy with and without calcium additions in the solution for 6 hours and the weight loss of the alloy was calculated relative to initial exposed surface area. The magnesium alloy that did not include calcium dissolved at a rate of 48 mg/cm.sup.2-hr. in the 3% KCl solution at 90° C. The magnesium alloy that included calcium dissolved at a rate of 91 mg/cm.sup.2-hr. in the 3% KCl solution at 90° C. The corrosion rates were also tested in fresh water. The fresh water is water that has up to or less than 1000 ppm salt content. A KCl brine solution was used to compare the corrosion rated of the magnesium alloy with and without calcium additions. 1″×0.6″ samples of the magnesium alloy with and without calcium additions were submerged in the 0.1% KCL brine solution for 6 hours and the weight loss of the alloys were calculated relative to initial exposed surface area. The magnesium alloy that did not include calcium dissolved at a rate of 0.1 mg/cm.sup.2-hr. in the 0.1% KCl solution at 90° C., a rate of <0.1 mg/cm.sup.2-hr. in the 0.1% KCl solution at 75° C., a rate of <0.1 mg/cm.sup.2-hr. in the 0.1% KCl solution at 60° C., and a rate of <0.1 mg/cm.sup.2-hr. in the 0.1% KCl solution at 45° C. The magnesium alloy that did include calcium dissolved at a rate of 34 mg/cm.sup.2-hr. in the 0.1% KCl solution at 90° C., a rate of 26 mg/cm.sup.2-hr. in the 0.1% KCl solution at 75° C., a rate of 14 mg/cm.sup.2-hr. in the 0.1% KCl solution at 60° C., and a rate of 5 mg/cm.sup.2-hr. in the 0.1% KCl solution at 45° C.

(21) The effect of calcium on magnesium alloy revealed that the microscopic “cutting” effect of the lamellar aluminum-calcium phase slightly decreases the tensile strength at room temperature, but increased tensile strength at elevated temperatures due to the grain refinement effect of Al.sub.2Ca. The comparative tensile strength and elongation to failure are shown in Table A.

(22) TABLE-US-00001 TABLE A Tensile Tensile Strength Elongation to Strength Elongation to Test without failure without with 2 wt. % failure with 2 Temperature Ca (psi) Ca (%) Ca (psi) wt. % Ca (%)  25° C. 23.5 2.1 21.4 1.7 150° C. 14.8 7.8 16.2 6.8

(23) The effect of varying calcium concentration in a magnesium-aluminum-nickel alloy was tested. The effect on ignition temperature and maximum extrusion speed was also tested. For mechanical properties, the effect of 0-2 wt. % calcium additions to the magnesium alloy on ultimate tensile strength (UTS) and elongation to failure (Ef) is illustrated in Table B.

(24) TABLE-US-00002 TABLE B Calcium UTS at E.sub.f at UTS at E.sub.f at Concentration (wt. %) 25° C. 25° C. 150° C. 150° C. .sup. 0% 41.6 10.3 35.5 24.5 0.5% 40.3 10.5 34.1 24.0 1.0% 38.5 10.9 32.6 23.3 2.0% 37.7 11.3 31.2 22.1

(25) The effect of calcium additions in the magnesium-aluminum-nickel alloy on ignition temperature was tested and found to be similar to a logarithmic function, with the ignition temperature tapering off. The ignition temperature trend is shown in Table C.

(26) TABLE-US-00003 TABLE C Calcium Concentration (wt. %) 0 1 2 3 4 5 Ignition Temperature (° C.) 550 700 820 860 875 875

(27) The incipient melting temperature effect on maximum extrusion speeds was also found to trend similarly to the ignition temperature since the melting temperature of the magnesium matrix is limiting. The extrusion speed for a 4″ solid round extrusion from at 9″ round billet trends as shown in Table D.

(28) TABLE-US-00004 TABLE D Calcium Concentration (wt. %) 0% 0.5% 1% 2% 4% Extrusion Speed for 4″ solid (in/min) 4 6 9 12 14 Extrusion speed for 4.425″ OD × 1.5 2.5 4 7 9 2.645″ ID tubular (in/min)

Example 15

(29) Pure magnesium is heated to a temperature of 680-720° C. to form a melt under a protective atmosphere of SF6+CO.sub.2+air. 1.5-2 wt. % zinc and 1.5-2 wt. % nickel were added using zinc lump and pelletized nickel to form a molten solution. From 3-6 wt. % gadolinium, as well as about 3-6 wt. % yttrium was added as lumps of pure metal, and 0.5-0.8% zirconium was added as a Mg-25% zirconium master alloy to the molten magnesium, which is then stirred to distribute the added metals in the molten magnesium. The melt was then cooled to 680° C., and degassed using HCN and then poured in to a permanent A36 steel mold and solidified. After solidification of the mixture, the billet was solution treated at 500° C. for 4-8 hours and air cooled. The billet was reheated to 360° C. and aged for 12 hours, followed by extrusion at a 5:1 reduction ratio to form a rod.

(30) It is known that LPSO phases in magnesium can add high temperature mechanical properties as well as significantly increase the tensile properties of magnesium alloys at all temperatures. The Mg.sub.12Zn.sub.1-xNi.sub.x RE.sub.1 LPSO (long period stacking order) phase enables the magnesium alloy to be both high strength and high temperature capable, as well as to be able to be controllably dissolved using the phase as an in situ galvanic phase for use in activities where enhanced and controllable use of degradation is desired. Such activities include use in oil and gas wells as temporary pressure diverters, balls, and other tools that utilize dissolvable metals.

(31) The magnesium alloy was solution treated at 500° C. for 12 hours and air-cooled to allow precipitation of the 14H LPSO phase incorporating both zinc and nickel as the transition metal in the layered structure. The solution-treated alloy was then preheated at 350-400° C. for over 12 hours prior to extrusion at which point the material was extruded using a 5:1 extrusion ratio (ER) with an extrusion speed of 20 ipm (inch per minute).

(32) At the nano-layers present between the nickel and the magnesium layers or magnesium matrix, the galvanic reaction took place. The dissolution rate in 3% KCl brine solution at 90° C. as well as the tensile properties at 150° C. of the galvanically reactive alloy are shown in Table E.

(33) TABLE-US-00005 TABLE E Magnesium Alloy Ultimate Tensile Tensile Yield Elongation to Dissolution rate Strength at Strength at Failure at (mg/cm.sup.2-hr.) 150° C. (ksi) 150° C. (ksi) 150° C. (%) 62-80 36 24 38

(34) 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.