Intermetallic compound ultrafine particle reinforced metal-based composite material and preparation method thereof

Abstract

This invention disclosed a method for preparing the ultrafine intermetallic particles reinforced metal matrix composites (MMC). The particle size of ultrafine intermetallic particles is about 0.015 m. In this method, intermetallic particles and metal matrix were first ball milled together to get the mixed powder. Then, powders were cold-pressed then vacuum melting with metals to prepare the reinforced metal matrix composites materials. The intermetallic particles addition amount in this is 130 wt %. This invention improve the dispersion properties of intermetallic particles while increase the particle/matrix interface strength. The ultrafine intermetallic particles reinforced MMC shows the very good performance with good ductility and strength.

Claims

1. A preparation method of an ultrafine intermetallic particle reinforced metal matrix composite (MMC), including the following steps: Step 1: grinding reinforcement intermetallic particles and a metal additive together using a planetary ball mill to obtain a mixed composite powder with particle size 0.01-5m; Step 2: cold-pressing the mixed composite powder, at a pressure of 1-20 MPa, to obtain a pre-pressed block; Step 3: vacuum melting the pre-pressed block and metal elements of an alloy to obtain the ultrafine intermetallic particle reinforced MMC, wherein the reinforcement intermetallic particles are uniformly dispersed in an alloy matrix comprising the metal elements of the alloy in Step 3 and the metal additive; and the amount of the reinforcement intermetallic particles in the ultrafine intermetallic particle reinforced MMC is 1-30 wt %.

2. The preparation method according to claim 1, wherein the reinforcement intermetallic particles are rare earth metal compounds.

3. The preparation method according to claim 1, wherein the alloy in Step 3 is a magnesium alloy or an aluminum alloy.

4. The preparation method according to claim 3, wherein the magnesium alloy is a Mg-0.1-40wt % Li alloy.

5. The preparation method according to claim 1, wherein the metal additive is magnesium-based metal shavings or powder, aluminum metal shavings or powder.

6. The preparation method according to claim 1, wherein the mass ratio of the metal additive and the reinforcement intermetallic particles are from 1:3 to 3:1.

7. The preparation method according to claim 2, wherein the reinforcement intermetallic particles are YAl.sub.2 or CeAl.sub.2.

8. The preparation method according to claim 3, wherein the aluminum alloy is a Al-0.1-15wt % Li alloy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 Binary MgLi alloy phase diagram.

(2) FIG. 2 The sketched fabrication process ultrafine particle reinforced metal matrix composites in this invention.

(3) FIG. 3 Images of the interface characteristics of composites produced by the present invention

(4) FIG. 4 Microstructures of the composites

(5) FIG. 5 TEM image of YAl.sub.2/Mg mixture during preparation process of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) By referencing to the attached drawings and examples, the present invention is clarified in details:

(7) The present invention provides a fabrication process of intermetallic compound ultrafine particles reinforced metal matrix composites, and the sketched diagram of fabrication process of this MMC is shown in FIG. 2. The details are as follows: (1) The reinforcement intermetallic particles and metal additives were firstly mixed. Then the mixed powder was milled in a planetary ball mill to form a mixed composite powder. The reinforcement intermetallic particles, 0.015 m in diameter, can be the transition or rare earth intermetallic particles, such as YAl.sub.2 or CeAl.sub.2. The metal additives were powders of magnesium, aluminum, or pure metal. (2) The mix-milled composite powder was pre-compacted in 1MPa20MPa conditions to obtain pre-compressed blocks. The process of pre-compaction can prevent introducing excessive gas impurities and combustion when adding the ultrafine powder into the alloy matrix to reinforce the resultant MMC. (3) Pre-compressed blocks of the mixed composite powder were added into the melting metal matrix in melting process. Argon was used as the protection gas in this process. With the aid of mechanical and ultrasonic stirring, the reinforced metal matrix composites were prepared. The amount of metal elements in the metal additive should be accounted for when distributing the ratio of metal elements of the alloy matrix in the resultant MMC. In accordance with the requirements of the components of the alloy matrix in the reinforced metal matrix composites, the remaining amount of metal elements were added and melted into a melting metal matrix. Then pre-compressed blocks were added to the melting metal matrix. The amount of the prepared reinforcement intermetallic particles was 1-30 wt % in the reinforced metal matrix composites. The mechanical and ultrasonic stirring can help better dispersion of ultrafine particles, and to optimize the mechanical properties of the reinforced metal composites.

(8) The matrix described is magnesium alloys or aluminum alloys.

(9) The radius and the weight percentage of reinforcement particles in the metal matrix composites are 0.015 m, and 130 wt %, respectively. During the preparation process, the blocks with modified ultrafine reinforcement particles and metals additives were meted with remaining metals to avoid powders clusters for better dispersion. The results of the particles/metal interfacial microstructure and the mechanical properties of the composites show that: The intermetallic particles were uniformly distributed in metal, and a very strong metallic bond was formed between reinforced particles and metal alloys; the tensile strength of composites were improves while with acceptable plasticity. This will be explained in details in following examples:

EXAMPLE 1

(10) The following is a description of the method for processing of the Mg-14LiAl matrix composites with reinforced ultrafine particles YAl.sub.2 through stirring casting technique.

(11) 1. The monolithic YAl.sub.2 intermetallic were prepared in advance using molten technique under 1530 C. with 37.76 wt % Al and balance with Y, then the YAl.sub.2 were grinded down to powders (the mean size approximate to 5 microns) using mechanical crushed followed by high energy ball mill.

(12) Powder mixtures of Mg-66.7 wt. % YAl.sub.2 (YAl.sub.2 is 600 g, Mg is 300 g) were milled together in a planetary ball mill in air at room temperature for 2 hrs.

(13) 2. After mixing, the MgYAl.sub.2 powder mixture was cold-compacted to a bulk in a steel die set under 20 MPa.

(14) 3. The powder compacts be added to the alloy melt, an MgLiAl (composition in mass (g): 224 Li, 16 Al, 890 Mg) matrix metal and 30 wt % of YAl.sub.2 were casted together in a low carbon steel crucible.

(15) The test results show that, the tensile strength of YAl.sub.2p/MgLiAl composites at room temperature is 420 MPa, and increased by 200% than that of matrix alloy (122 MPa) with a good ductility and elongation higher than 7%.

EXAMPLE 2

(16) The following is a description of the method for processing of the Mg-14LiAl matrix composites with reinforced ultrafine particles YAl.sub.2 through stirring casting technique.

(17) 1. The monolithic YAl.sub.2 intermetallic were prepared in advance using molten technique under 1530 C. temperature and composition in mass %: 37.76 Al, balance Y, and then the YAl.sub.2 powders (the mean size approximate to 0.01 microns) were prepared by mechanical crushed and high energy ball mill.

(18) Powder mixtures of Mg-66.7 wt. % YAl.sub.2 (YAl.sub.2 is 20 g, Mg is 40 g) were milled together in a planetary ball mill under atmosphere at nominal room temperature for 2 hrs.

(19) 2. After mixing, the MgYAl.sub.2 powder mixture was cold-compacted to a bulk in a steel die under 20 MPa for 10 mins.

(20) 3. The powder compacts be added to the alloy melt, an MgLiAl (composition in mass (g): 227.2 Li, 19.8 Al, 1643 Mg) matrix metal and 1 wt % of YAl.sub.2 were casted together in a low carbon steel crucible.

(21) The test results show that, the tensile strength of YAl.sub.2p/MgLiAl composites at room temperature is 320 MPa, and increased by 160% than matrix alloy (122 MPa). In addition, the elongation of composite is decrease from 20% to 18%.

(22) FIG. 3 and FIG. 4 is a microstructure of the composite. It can be seen that, the YAl.sub.2 particles distributed uniformly in the MgLiAl matrix and had no cluster observed. There is an ideal direct bonding interface formed between YAl.sub.2 particles and MgLi matrix without interfacial interaction and de-bonding take place. The TEM photographs of the YAl.sub.2p/Mg interface after mixing was shown in FIG. 5. Good metallurgical bonds are obtained between YAl.sub.2 particles and magnesium. The YAl.sub.2Mg interface was bonded directly, free from any interfacial reactions products.

EXAMPLE 3

(23) The following is a description of the method for processing of the Mg-14LiAl matrix composites with reinforced ultrafine particles YAl.sub.2 through stirring casting technique.

(24) 1. The monolithic YAl.sub.2 intermetallic were prepared in advance using molten technique under 1530 C. temperature and composition in mass %: 37.76 Al, balance Y, and then the YAl.sub.2 powders (the mean size approximate to 0.1 microns) were prepared by mechanical crushed and high energy ball mill. Powder mixtures of Mg-66.7 wt. % YAl.sub.2 (YAl.sub.2 is 20 g, Mg is 40 g) were milled together in a planetary ball mill under atmosphere at nominal room temperature for 2 hrs.

(25) 2. After mixing, the MgYAl.sub.2 powder mixture was cold-compacted to a bulk in a steel die under 20 MPa for 10 mins.

(26) 3. The powder compacts be added to the alloy melt, an Mg-14LiAl (composition in mass (g): 227.2 Li, 19.8 Al, 1643 Mg) matrix metal and 1 wt % of YAl.sub.2 were casted together in a low carbon steel crucible.

(27) The test results show that, the tensile strength of YAl.sub.2p/MgLiAl composites at room temperature is 270 MPa, and increased by 120% than that of matrix alloy (122 MPa). In addition, the elongation of composite is decrease from 20% to 17%.

EXAMPLE 4

(28) The following is a description of the method for processing of the Mg-14LiAl matrix composites with reinforced ultrafine particles YAl.sub.2 through stirring casting technique.

(29) 1. The monolithic YAl.sub.2 intermetallic were prepared in advance using molten technique under 1530 C. temperature and composition in mass %: 37.76 Al, balance Y, and then the YAl.sub.2 powders (the mean size approximate to 3 microns) were prepared by mechanical crushed and high energy ball mill.

(30) Powder mixtures of Mg-66.7 wt. % YAl.sub.2 (YAl.sub.2 is 20 g, Mg is 40 g) were milled together in a planetary ball mill under atmosphere at nominal room temperature for 2 hrs.

(31) 2. After mixing, the MgYAl.sub.2 powder mixture was cold-compacted to a bulk in a steel die set under 20 MPa.

(32) 3. The powder compacts be added to the alloy melt, a Mg-14Li-3Al (composition in mass g: 227.2 Li, 32.7 Al, 1630.1 Mg) matrix metal and 1 wt % of YAl.sub.2 were casted together in a low carbon steel crucible.

(33) The test results show that, the tensile strength of YAl.sub.2p/MgLiAl composites at room temperature is 180 MPa, and increase over past 50% than that of matrix alloy (122 MPa) with a good ductility and elongation higher than 16%.

EXAMPLE 5

(34) The following is a description of the method for processing of the Mg-40Li matrix composites with reinforced ultrafine particles CeAl.sub.2 through stirring casting technique.

(35) 1. The monolithic CeAl.sub.2 intermetallic were prepared in advance using molten technique under 1500 C. temperature and composition in mass %: 37.78 Al, balance Ce, and then the CeAl.sub.2 powders (the mean size approximate to 1 microns) were prepared by mechanical crushed and high energy ball mill.

(36) Powder mixtures of Mg-75 wt. % CeAl.sub.2 (CeAl.sub.2 is 300 g, Mg is 100 g) were milled together in a planetary ball mill under atmosphere at nominal room temperature for 2 h.

(37) 2. After mixing, the MgCeAl.sub.2 powder mixture was cold-compacted to a bulk in a steel die set by using a pressure of 1 MPa.

(38) 3. The powder compacts be added to the alloy melt, a Mg-40Li (composition in mass g: 680 Li, 920 Mg in the alloy melt) matrix metal and 15 wt % CeAl.sub.2 were casted together in a low carbon steel crucible.

(39) The test results show that, the tensile strength of CeAl.sub.2p/MgLi composites at room temperature is 180 MPa, and increase over past 150% than that of matrix alloy (70 MPa) with a good ductility and elongation higher than 20%.

EXAMPLE 6

(40) The following is a description of the method for processing of the AlCuLi matrix composites with reinforced ultrafine particles YAl.sub.2 through stirring casting technique.

(41) 1. The monolithic YAl.sub.2 intermetallic were prepared in advance using molten technique under 1530 C. temperature and composition in mass %: 37.76 Al, balance Y, and then the YAl.sub.2 powders (the mean size approximate to 0.5 microns) were prepared by mechanical crushed and high energy ball mill.

(42) Powder mixtures of 66.7 wt. % Al.sub.2Cu and 33.3 wt. % YAl.sub.2 (YAl.sub.2 is 20 g, Al.sub.2Cu is 40 g) were milled together in a planetary ball mill under atmosphere at nominal room temperature for 40 h.

(43) 2. After mixing, the Al.sub.2CuYAl.sub.2 powder mixture was cold-compacted to a bulk in a steel die under 20 MPa.

(44) 3. The powder compacts be added to the alloy melt, a AlCuLiZrMn (composition in mass (g): 1873.3 Al, 27.9 Li, 33.1 Cu, 2.4 Zr, 3.3 Mn in the alloy melt) matrix metal and 1 wt % YAl.sub.2 were casted together in a low carbon steel crucible.

(45) The test results show that, the tensile strength of YAl.sub.2p/MgLiAl composites at room temperature is 460 MPa, and increase over past 50% than that of matrix alloy (206 MPa). In addition, the elongation of composite is decrease from 17% to 15%.

(46) The intermetallic having a high specific strength and stiffness, it can be used as effectively reinforcement material for magnesium-lithium alloy, aluminum-aluminum alloy and lithium alloy composites. Compared with the ceramics reinforcements, intermetallic have good wet properties due to the existence of the metallic bonds. The element Y, Ce and Al addition can improve materials wettability between the reinforced and matrix alloy. In addition, Al can improve composites strength, while Y and Ce can be as the grain refinerm therefore improve composites mechanical properties, anti-oxidation and creep deformation resistant. Compare to use ceramic as the strengthener, intermetallic reinforcement composites have good ductility and interfacial coherency, which inhibits the cracks propagation in composites. By the used of ultrafine intermetallic particles as the strengthener, the material strengthening mechanisms were changed, therefore, composites have better mechanical properties. As it was known, the strengthening efficiency was mainly dependent on the load transfer properties between the metal matrix composites and reinforced particles, the ultrafine particles reinforced MMC enhanced the dispersion hardening effect. Meanwhile, due to the reduce of particle size, the particle surface activity was increased, the bonding strength between particles and matrix are largely enhanced. Hence, the particles/matrix interfacial bonding strength, the particles dispersion ability and microstructure uniformly are the main reason to influence composites strength and ductility. According to the similarity properties of the rare earth compounds, the intermetallic strengthener also can use ScAl intermetallics, LaAl intermetallics and other intermetallics in MMC materials with excellent mechanical properties, they can be used in automobile, aerospace industries and other fields.