激光沉积TA15钛合金损伤容限性能研究

Study on Damage Tolerance Properties of TA15 Titanium Alloy by Laser Deposition Manufacturing

采用激光沉积制造技术制备TA15钛合金裂纹扩展速率(da/dN)以及平面应变断裂韧度(KIC)试样,采用金相显微镜(OM)以及扫描电子显微镜(SEM)观察微观组织与断口形貌。结果表明:沿沉积高度方向,组织呈现典型的β晶粒外延生长,β晶粒内部为α/β片层及集束组成的网篮组织;三种扩展方向下,YOZ面裂纹扩展速率最快,XOY面裂纹具有较低的扩展速率;平面应变KIC受裂纹预制扩展方向和β晶粒位向影响,表现为各向异性。裂纹扩展平面垂直β柱状晶时,KIC最大达86.36 MPa·m^(1/2),当β柱状晶位于裂纹扩展平面内,且平行于裂纹扩展方向时,KIC值为77.19 MPa·m^(1/2),β柱状晶垂直于裂纹扩展方向时,其对裂纹阻滞作用弱,KIC最小为56.16 MPa·m^(1/2)。

Samples of TA15 titanium alloy used in the test of crack propagation rate（da/dN）and plane strain fracture toughness （KIC） test is fabricated by laser deposition manufacturing（LDM）. Fatigue fracture surface and microstructure were examined by optical microscopy（OM）and scanning electron microscopy（SEM）. The results show that along the deposition direction micro-structure is epitaxial growth of typical β grains, and the basket-weave microstructure is composed of α/ β sheets and bundles inside the β grains. Under the three expansion directions, crack in YOZ plane has the fastest crack propagation rate, while crack in XOY plane has relatively slow crack propagation rate. KIC property presents anisotropism which is subjected to precast crack propagation direction and β grain orientation. If crack propagation runs the direction perpendicular to β grain boundary, KIC reaches the maximum 86.36 MPa ·m1/2. If the 13 grain locates in the crack propagation plane and is parallel to crack propa-gation direetion,KIC reaches 77.19 MPa·m1/2. If it is perpendicular to crack propagation direction, it has little impact on bloc-king crack propagation with KIC the minimum 56.16 MPa · m1/2.