Al-Li P/M materials with dispersion of ceramic or intermetallic compound particles

应用机械合金化工艺研究了陶瓷颗粒在铝锂合金中的分散，这种工艺能够生产出传统熔炼和铸造技术难以或不可能获得的合金。采用的基体合金为Al-2.5Li和Al-2.5Li-1.2 cu -0.7 mg， AL_2O3、TiC和A6_4C_3的陶瓷颗粒按2或6 vo1%的比例添加。以机械合金粉末为原料，经冷压和热挤压制备粉末冶金材料。为了尽量减少活性锂的氧化损失，整个过程都在氩气环境中进行。对制备的P/M材料进行了金相、拉伸试验和时效硬化试验。通过机械合金化，使陶瓷颗粒在铝锂合金基体中分散均匀。所得到的粉末冶金材料由于拉伸强化而具有较高的硬度。然而，时效硬化明显受到抑制，这可能是由于位错、亚边界和相间边界等非均相析出部位的增加。这并不是含有Li的粉末冶金材料所特有的，因为在由机械合金化粉末加工的Al-Cu和Al-CuMg粉末冶金材料中也观察到同样的行为。然而，由于陶瓷颗粒的良好分散，这些P/M材料表现出很高的强度。分散度为2vo1% TiC或AL_2O_3的Al-Li-Cu-Mg P/M合金在挤压状态下的抗拉强度高达600 MPa。陶瓷添加量的进一步增加导致延伸率下降，从而导致拉伸强度下降。这些易碎的P/M材料表现得更像陶瓷，而不是金属，因为它们的抗拉强度低于硬度转换后的值。比弹性模量高达30 GPa，比强度高达225 MPa，远高于7075-T6。

Dispersion of ceramic particles has been studied in Al-Li alloys by applying mechanical alloying process which enables to produce alloys that are difficult or impossible to obtain by conventional melting and casting techniques. The matrix alloys used were Al-2.5Li and Al-2.5Li-1.2Cu-0.7Mg, and ceramic particles of AL_2O3, TiC and A6_4C_3 were added by the amount of 2 or 6 vo1%. P/M materials were produced from mechanically alloyed powders by cold pressing and hot extrusion. processing was all done in an argon atmoshpere so as to minimize oxidation loss of active Lithium. Metallography, tensile testing and age-hardening behavior were examined on obtained P/M materials.Fine and uniform dispersion of ceramic particles in the matrix of Al-Li alloys was attained by mechanical alloying. Obtained P/M materials showed high hardness due to despersion strengthening. However, age hardening was remarkably suppressed probably due to increased heterogeneous precipitation sites such as dislocation, subboundary and interphase boundary. This is not peculiar to P/M materials containing Li, since the same behavior was observed in Al-Cu and Al-CuMg P/M materials processed from mechanically alloyed powder. Nonetheless, these P/M materials showed high strength due to fine dispersion of ceramic particles. Al-Li-Cu-Mg P/M alloy with dispersion of 2 vo1% TiC or AL_2O_3 showed tensile strength as high as 600 MPa in as extruded condition. Further increase of ceramic addition caused decrease of elongation and thus tensile strength. These brittle P/M materials behave more like ceramics rather than metals, since they showed lower tensile strength than the converted values from their hardness. Specific elastic modulus was as high as 30 GPa and specific strength as high as 225 MPa, much higher than those of 7075-T6.