TC17合金焊接接头显微组织与疲劳裂纹扩展特性

Microstructure and Fatigue Crack Growth Characteristics of Welded Joints of TC17 Titanium Alloy

研究了TC17钛合金惯性摩擦焊焊接接头的疲劳裂纹扩展规律,并利用光学显微镜、扫描电镜对材料的显微组织和断口形貌进行分析。结果表明:TC17钛合金母材为α+β网篮状组织,晶粒较大;焊缝区和热影响区内可以看到明显的原β相晶界,焊缝区的原β晶粒较细小,热影响区的原β晶粒较粗大,晶粒内部存在细小的α相。在室温下,当ΔK≤15 MPa.m1/2时,焊缝区疲劳裂纹扩展速率较小,而当ΔK≥15 MPa.m1/2时,焊缝区的扩展速率最大,其次是热影响区,母材的裂纹扩展速率最小;在高温下,焊接接头各部位的裂纹扩展速率相差不大,均小于室温。

The fatigue crack growth rate of inertia friction welded joints of TC17 titanium alloy was studied.The microstructure and the fracture surface were analyzed by means of optical microscopy and scanning electron microscopy.The results show that the microstructure of TC17 titanium alloy is α+β phase with bigger grain.The microstructure of weld zone and heat affected zone is tiny α phase and clear β phase grain boundary,the original β grain of weld zone is smaller,the original β grain of heat affected zone is bigger.At room temperature;when ΔK≤15 MPa·m1/2,the fatigue crack growth rate of weld zone is smaller;when ΔK≥15 MPa·m1/2,the fatigue crack growth rate of weld zone is the largest.The next is heat affected zone,the growth rate of parent metal is the smallest.At high temperature,the fatigue crack growth rate of different parts of welded joints shows little difference,but all lower than those tested at room temperature.