激光沉积TA15钛合金显微组织及高周疲劳性能研究

Study on microstructure and high cycle fatigue property of laser deposited TA15 titanium alloy

对激光沉积TA15钛合金显微组织进行研究,并分析了室温下高周疲劳裂纹的萌生和扩展特性。采用光学显微镜(OM)和扫描电子显微镜(SEM)分析了试样疲劳断口以及纵截面显微组织形貌。研究表明,激光沉积宏观组织呈现定向生长的柱状晶形貌,晶粒内部为细小的网篮组织,经过双重退火后,网篮组织有粗化趋势。疲劳源区存在与α集束尺寸相当的解理断裂平面,稳定扩展区疲劳裂纹扩展路径曲折,这与片层组织中α集束位向不同有关,一定区域内疲劳裂纹平行α片层或近似垂直α片层扩展,扩展区的二次裂纹有助于扩展能量的消耗,提高疲劳寿命。

The microstructure of laser deposited TA15 titanium alloy was investigated and high cycle fatigue property including crack initiation and crack propagation at room temperature was analyzed.The fatigue fracture surface and microstructure of longitudinal section were examined by optical microscopy(OM)and scanning electron microscopy(SEM).The results indicate that as-deposited macrostructure consists of directional column grains with extremely fine basket-weave microstructure.After double-annealing treatment,coarse lamellar-like basket-weave microstructure was obtained.The crack initiation region was characterized by crystallographic cleavage facets ofαlamellar.The crack tended to propagate tortuously,which was related to different orientations ofαlamellar.Its propagation direction in certain areas was parallel or approximately perpendicular toαlamellar and the secondary cracks in the crack propagation region helped consuming energy and improved the fatigue life.