利用液氮低温球磨技术制备了纳米晶Al-Zn-Mg-Cu合金粉体,分析了材料在球磨过程中微观组织变化.结果表明, 气雾化Al-Zn-Mg-Cu合金粉体随着球磨过程的进行晶粒尺寸逐渐减小, 球磨15 h后晶粒尺寸约为35 nm；MgZn2相逐步分解, 并最终过饱和固溶于α-Al中. 制备的纳米晶Al-Zn-Mg-Cu合金粉体低于709 K(0.77 Tm, Tm 为熔点)加热时, 晶粒长大速度缓慢; 709 K加热1 h 晶粒尺寸仅为71 nm. 研究表明, 液氮低温球磨过程中形成的Al2O3颗粒对晶粒的钉扎有效地提高了纳米晶Al-Zn-Mg-Cu合金粉体的热稳定性.
Nanocrystalline Al-Zn-Mg-Cu alloy powders have been successfully fabricated by mechanically milling at cryogenic temperature (cryomilling) in liquid nitrogen. Microstructural evolution of the alloy powders during cryomilling was analyzed. The experimental results show that the as-atomized Al-Zn-Mg-Cu alloy powder size was gradually reduced and approached 35 nm after 15 h cryomilling. MgZn2 phase gradually disappeared and ultimately was super-saturated into α-Al. No significant grain growth for the nanocrystalline Al-Zn-Mg-Cu alloy was found when it was heated at or below 709 K, for example, the average grain size of the milling alloy heated at 709 K for 1 h is only 71 nm. The results obtained herein suggest that the significant thermal stability of the cryomilled Al-Zn-Mg-Cu material may be attributed to the presence of nano-scale Al2O3 particles.
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