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

采用机械合金化工艺研究了陶瓷颗粒在Al-Li合金中的分散性，该工艺能够生产出用常规熔炼和铸造技术难以或不可能获得的合金。基体合金为Al-2.5Li和Al-2.5Li-1.2Cu-0.7Mg，陶瓷颗粒为Al_2O_3、TiC和A_6_4C_3，添加量分别为2%和6%（体积分数）。以机械合金化粉末为原料，采用冷压和热挤压工艺制备粉末冶金材料。处理全部在氩气氛中进行，以使活性锂的氧化损失最小化。对所制备的粉末冶金材料进行了金相、拉伸试验和时效硬化行为的研究。所获得的粉末冶金材料由于弥散强化而显示出高的硬度。然而，时效硬化显着抑制可能是由于增加的非均匀析出的网站，如位错，亚边界和相间边界。这并不是含Li的P/M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 P/M材料中观察到了相同的行为。尽管如此，由于陶瓷颗粒的精细分散，这些P/M材料显示出高强度。Al-Li-Cu-Mg系粉末冶金合金在挤压态时，TiC或Al_2O_3的含量为2vo1%时，抗拉强度可达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。这些脆性粉末冶金材料的行为更像陶瓷而不是金属，因为它们的拉伸强度低于从它们的硬度转换的值。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.