低温球磨和真空热压技术制备的纳米晶纯铝块体的强化机理

利用液氮球磨和真空热压技术制备了纳米晶纯铝块体材料。采用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)对材料的晶粒尺寸和微观组织进行研究,分析了影响热稳定性的因素和强化机理。研究表明,液氮球磨以后材料晶粒尺寸为37nm,经过真空热压和热挤压后晶粒有所长大,晶粒大小约300nm,纳米晶结构基本得到保持。分析晶粒热稳定性的原因在于球磨过程中生成的AlN等粒子的晶界钉扎以及引入的杂质溶质的拖拽作用。纳米晶纯铝块体的拉伸强度极限σb为173MPa,伸长率fε为17.5%。

Strengthening mechanism of bulk nanocrystalline Al prepared by cryomilling and hot pressing in vacuum

The bulk nanocrystalline Al was fabricated by mechanically milling at cryogenic temperature(cryomilling) and then hot pressing in vacuum.By X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM),the grain size and microstructure evolution of the sample during cryomilling and consolidation were investigated.The grain size reduces to 37 nm after cryomilling for 12 hours.The grain grows up to about 300nm under the hot pressing and extrusion.The nanostructure can be kept even during consolidation.The reason of high thermal stability of this bulk is attributed primarily to the Zener pinning from grain boundary of the AlN arising from cryomilling and the solute drag of the impurity.The tensile ultimate strength and elogation of the bulk nanocrystalline Al are 173MP and 17.5%,respectively.