粉末冶金碳化物强化铌合金组织演变及其力学行为

采用机械球磨与热压烧结相结合的粉末冶金法对不同球磨时间Nb-35Ti-6Al-5Cr-8V-5C合金的粉末变形行为,微观组织结构和力学行为进行研究。结果表明:随着球磨时间的增加,Nb-35Ti-6Al-5Cr-8V-5C复合粉末中的块状金属颗粒首先变形为片状后在碰撞挤压作用下破碎成絮状,TiC粉末均匀的分布于片状金属粉末表面;Nb-35Ti-6Al-5Cr-8V-5C合金由Nbss和(Nb,Ti)C两相构成,各合金碳化物体积分数均为11%左右,Ti元素主要分布于Nbss晶界和碳化物内,Al、Cr、V元素主要分布于Nbss晶粒内,Nbss和(Nb,Ti)C相尺寸均随球磨时间增加而尺寸减小;Nbss晶粒细化及强化相碳化物弥散化导致合金的室温压缩力学性能和塑性变形能力显著提高,压缩变形后合金Nbss与碳化物具有良好的界面结合能力,但是碳化物内部存在明显的近似平行分布的裂纹;数据对比表明,粉末冶金法制备Nb-35Ti-6Al-5Cr-8V-5C合金的力学性能优于电弧熔炼法。

Microstructure evolution and mechanical behavior of powder metallurgy carbide-reinforced Niobium alloy

The powder deformation behavior, microstructure evolution and mechanical properties of the Nb-35Ti-6Al-5Cr-8V-5C alloys after different ball milling time were investigated using powder metallurgy method by the combination of mechanical alloying and hot press sintering. The result show that the massive metal particles of Nb-35Ti-6Al-5Cr-8V-5C mixed powder are translated into flakes morphology firstly and then deformed into flocculent morphology during the action of impact extrusion as the ball milling time increasing, as well as the TiC powders are distributed uniformly on the surface of flake metal powder. The Nb-35Ti-6Al-5Cr-8V-5C alloy is consisted of Nbss phase and (Nb, Ti)C phase, and the volume of carbide for each alloy is about 11%. The element of Ti is mainly distributed in (Nb, Ti)C and the grain boundary of Nbss, however the element of Al, Cr, V is mainly distributed in Nbss grain. The size of Nbss and (Nb, Ti)C phase is decreased with the increasing of ball milling time. The compressive mechanical properties and plastic deformation capacity at room temperature is significantly increased causing by grain refinement of Nbss and reinforced phase dispersion of carbides. After compression deformation Nbss and carbide have good interfacial bonding, however, the obvious crack with a nearly parallel distribution inside carbides is existed. Furthermore, it is evident that the mechanical property of Nb-35Ti-6Al-5Cr-8V-5C alloy prepared by powder metallurgy is better than that prepared by arc melting method.