TC4钛合金锯齿形切屑绝热剪切带的微观组织和显微硬度变化

使用金相显微镜、透射电子显微镜观察了TC4钛合金在不同切削速度下形成的锯齿形切屑的绝热剪切带的微观组织形貌,测量了绝热剪切带的显微硬度。结果表明,在较低切削速度下,绝热剪切带为形变带;在较高切削速度下,绝热剪切带为由细小等轴晶粒和局部发生了β相转变为α″相的马氏体相组成的转变带;随着切削速度的进一步提高,在绝热剪切带中观察到了非晶化这一新现象。无论绝热剪切带是形变带还是转变带,其显微硬度都随切削速度的增大而增大。根据绝热剪切带微观组织和显微硬度的变化规律,绝热剪切带显微硬度的强化可分为三个阶段:形变强化、细晶和马氏体相变强化、非晶强化。

Investigation on Microstructure and Microhardness of Adiabatic Shear Band of Saw-tooth Chip in Machining TC4 Alloy

Microstructure of ASB of saw-tooth chip produced in different cutting speeds was observed and analyzed by optical microscope and TEM in machining of TC4 alloy.The microhardness of ASB was also measured.Experimental results show that ASB formed at low cutting speed is deformed band,at higher cutting speed,ASB becomes transformed band composed of fine equiaxed grains and martensitic phase that comes from phase transformation β→α″.With the further increase of cutting speed,amorphization that had not been observed before occurence inside ASB.The microhardness of ASB always increases with the increasing of cutting speed whatever the ASB is deformed or transfromed band.According to the law of microstructure evolution and the increase of microhardness of ASB,the microhardness increase can be divided into three stages: strain-hardening,grain refining and martensitic phase transformation hardening,amorphization hardening.