TC21钛合金线性摩擦焊接头组织及性能分析

Microstructure and Properties of Linear Friction Welded Joint of TC21 Titanium Alloy

本研究对TC21钛合金进行线性摩擦焊接试验,采用OM、SEM等测试手段对接头各区域显微组织演变规律进行了分析,并通过显微硬度仪和电子万能试验机对接头显微硬度及拉伸性能进行测试。结果表明:TC21钛合金线性摩擦焊可以得到良好的焊接接头,接头明显分为母材区、热力影响区和焊缝区;焊接过程中焊缝区发生了相变及动态再结晶过程,形成细小的再结晶晶粒,板条状α相在晶界处析出,针状马氏体α′相在晶粒内部析出,并有少量的残余α相保留至室温;热力影响区主要以变形α相为主,随着远离焊缝中心,再结晶程度逐渐减弱,α相比例逐渐增加。由于飞边形成阶段及焊后冷却速率大小不同,导致沿着焊缝中心向飞边端部靠近,晶粒尺寸逐渐变大。TC21钛合金线性摩擦焊接头显微硬度呈拱形分布,焊缝中心显微硬度值(HV)达到最大值4508 MPa,拉伸性能测试结果表明,接头强度与母材相当。

In this study,the linear friction welding of TC21 titanium alloy was investigated.The microstructure evolution of each region of the joint was analyzed by OM and SEM.The microhardness and tensile properties of the joint were tested by a microhardness tester and an electronic universal testing machine.The results show that a sound weld joint can be obtained using LFW.The joint is obviously divided into base metal zone(BM),thermo-mechanically affected zone(TMAZ)and weld zone(WZ).During the welding process,phase transformation and dynamic recrystallization take place in WZ,forming fine recrystallized grains,lathαprecipitated at grain boundary,acicular martensiteαphase precipitated inside grain,and a few residualαphase remains at room temperature.TMAZ is mainly dominated by deformedαphase.Away from the weld center,the degree of recrystallization gradually decreases and the proportion ofαphase gradually increases.Due to the difference of flash formation phase and cooling rate after welding,the grain size gradually increases from the weld center to the end of flash.The microhardness distribution of TC21 titanium alloy linear friction welded joint is arched,and the maximum value of microhardness(HV)in weld center is 4508 MPa.The tensile test results indicate that the strength of the joint is equivalent to that of the base metal.