超大挤压变形对钛合金增强镁基复合材料显微组织的影响

Effect of Ultra-Deformation on the Microstructures of Titanium Alloy Reinforced Magnesium Matrix Composites

摘要:

采用粉末冶金法制备了钛合金（Ti-6Al-4V）（质量分数，下同）颗粒增强MB15镁基复合材料，经225：1的超大比热挤变形后，借助光学显微镜（OM）、扫描电镜（SEM）和透射电镜（TEM）对其显微组织进行了研究。结果表明：钛合金颗粒沿挤压方向因塑性变形而被拉长，其增强效果得到提高；超大比热挤变形能够显著细化基体晶粒，并提高复合材料的组织均匀性；此外，原镁粉表面的氧化膜经超大比变形后得到了有效的碎化和分散，具有一定的弥散强化效果，因此可充当粉末冶金制备镁基复合材料的辅助增强相。

Abstract:

Magnesium matrix composite reinforced by titanium alloy (Ti-6Al-4V) particulate was fabricated by powder metallurgy route. The samples of composite were hot-extruded with an ultra-deformation ratio of 225:1. The microstructures of extruded samples were investigated using optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the Ti-6Al-4V particulates were apparently elongated along the extrusion direction, thus increased its reinforcing effect on the matrix. The ultra-deformation could markedly decrease the grain sizes of the composite matrix, and greatly improve the homogeneity of microstructures when compared with a lower ratio of extrusion deformation; in addition, the oxide layers on the surface of original Mg particles were effectively broken and dispersed randomly in the vicinity of Mg-Mg interfaces. It produced an oxidedispersion-strengthening (ODS) effect, further reinforced the matrix as a kind of secondary reinforcement.