激光沉积修复TA15激光沉积件的组织和疲劳性能

Microstructure and Fatigue Properties of Laser Deposition Repaired TA15 Titanium Alloy Manufactured by Laser Deposition

采用激光沉积修复技术(LDR)对TA15激光沉积件(LDM)内部损伤进行修复,研究修复后的组织与疲劳性能,并与原沉积试样进行对比。结果表明,修复试样整体组织均为网篮组织,母材区组织尺寸相比修复区较为粗大,两区之间的热影响区由大到小逐渐过渡;修复试样的疲劳极限为540 MPa略低于原沉积试样的555 MPa,但应力水平较高时,修复试样组织细小的优势突出,疲劳性能高于原沉积试样;修复试样具有较强的组织敏感性,疲劳裂纹均起源于气孔,裂纹源区有明显的α,β片层撕裂特征并有与其尺寸相当的解理台阶出现。裂纹扩展初期,组织敏感尺寸较小,易在多个取向相同的α片层处偏转,裂纹扩展后期,组织敏感尺寸增大,裂纹更易在粗大的α晶界处偏转。同时二次裂纹常伴随出现,增加能耗,提高疲劳寿命。

Laser deposition repairing(LDR) technology was used to repair the laser deposition manufactured(LDM) TA15 titanium alloy with defects. The repaired microstructure and fatigue properties were investigated and compared with the original samples. The results showed that the whole repaired microstructure was basketweave. The size of substrate microstructure was larger than that of the repaired zone and gradually changed from large to small in the heat affected zone between two zones. The fatigue strength of the repaired samples was 540 MPa, which was slightly lower than 555 MPa of the laser deposition manufactured samples. However, when the stress level was high, the small size of the repaired microstructure was prominent, and the fatigue life was higher than that of the laser deposited samples. The repaired part had strong microstructure sensitivity, and all the fatigue crack source from the pore. The crack initiation region was characterized by obvious α, β lamellar tearing and crystallographic cleavage facets of them. At the initial stage of crack propagation, the sensitive structure of the tissue was small, and it was easy to deflect at some α lamellar with the same orientation. At the late stage of crack propagation, the tissue sensitive size increased,and the crack was easily to deflect at the coarse α grain boundary. Secondary cracks often occurred at the same time and increased energy consumption and fatigue strength.