激光立体成形TC4合金的显微组织和拉伸性能

Microstructure and Tensile Properties of Laser Solid Formed TC4 Alloy

采用激光立体成形技术制备TC4合金(沉积态)并进行退火处理,研究了沉积态和退火态合金的显微组织和拉伸性能,并与传统TC4合金的进行了对比。结果表明:激光立体成形合金的沉积态显微组织主要由针状马氏体α和β相组成,原始β晶界清晰可见,退火态显微组织由α板条和板条间β相组成;与沉积态组织相比,退火态组织中α相的体积分数增加,α板条粗化;沉积态和退火态激光立体成形合金的拉伸性能均优于传统退火态TC4合金的,退火处理降低了合金在垂直于和平行于扫描方向上的性能差异;与沉积态合金的相比,退火态合金在平行于扫描方向上的抗拉强度和屈服强度下降,伸长率和断面收缩率增大,在垂直于扫描方向上二者的拉伸性能相差很小;沉积态和退火态合金的拉伸断口均呈韧窝特征,断裂机制均为韧性断裂。

TC4 alloy was prepared by laser solid forming（as-deposited）and then annealed.The microstructure and tensile properties of the as-deposited and annealed alloy were studied and compared with those of convertional TC4 alloy.The results show that the as-deposited microstructure of laser solid formed alloy consisted of needle-shaped martensiteαandβphases.The originalβgrain boundaries were observed clearly.The annealed microstructure was composed ofαlath andβphase between laths.Comparing with the as-deposited structure,the volume fraction ofαphase in the annealed structure increased and theαlath became coarse.The tensile properties of the laser solid formed alloy in as-deposited and annealed states were better than those of annealed conventional TC4 alloy.The annealing treatment decreased the property difference of the alloy between directions vertical and parallel to the scanning direction.Comparing with those of the as-deposited alloy,the tensile strength and yield strength of the annealed alloy decreased while the elongation and reduction of area increased.The tensile properties in vertical to the scanning direction of the as-deposited alloy and annealed alloy had little difference.The tensile fracture of the asdeposited and annealed alloys both showed a dimpled characteristic,and the fracture mechanism was ductile.