采用激光三维(3D)打印技术制备了TC4厚壁件,利用光学显微镜、扫描电子显微镜(SEM)、X射线衍射仪(XRD)及电子万能试验机等研究了正火温度对激光3D打印TC4钛合金显微组织、相组成、室温拉伸性能的影响规律。结果表明:当在α-Ti相单相区内正火处理时,α-Ti相再结晶生长,长、宽均增加;组织主要由α-Ti相组成,含有少量(或微量)β-Ti相;合金的室温拉伸性能一般。当在α+β两相区内正火处理时,沉积态下的细长状初生α-Ti相由于β-Ti相析出而被截断,变成短棒状初生α-Ti相;β-Ti相不仅与次生α-Ti相共存于短棒状初生α-Ti相之间,还会在短棒状初生α-Ti相内部呈网状析出。经990 ℃/2 h/AC处理后,合金的室温抗拉强度为960 MPa,屈服强度为835 MPa,断后伸长率为17%,达到了锻件国标要求。拉伸试样断口上均布满韧窝,均为延性断裂。

In this study, TC4 titanium alloy bulk specimens are prepared using the laser three-dimensional(3D)printing technology. The effect of normalizing temperature on the laser 3D-printed TC4 titanium alloy microstructure, phase composition, and tensile properties at room temperature is studied via an optical microscope, scanning electron microscopy (SEM), X-ray diffractometer (XRD), and electronic universal testing machine. Experimental results reveal that the α-Ti phase recrystallizes and the length and width of the α-Ti phase increase after being normalized at the α-Ti phase zone. The microstructures mainly comprise α-Ti phase and a small amount (or trace amount) of the β-Ti phase. The tensile property at room temperature is general. After being normalized at the α+β phase zone, the slender primary α-Ti phase in the as-deposited state thrusts each other because of the β-Ti phase precipitation, transforming into a short rod-shaped primary α-Ti phase. The β-Ti phase not only coexists with the secondary α-Ti phase between the short rod-shaped primary α-Ti phases, but also precipitates and is distributed as networks inside the short rod-shaped primary α-Ti phase. After 990 ℃/2 h/AC treatment, the room-temperature tensile strength, yield strength, and elongation are 960 MPa, 835 MPa, and 17%, which satisfy the national standard for forging. The fracture morphology of the tensile specimens is covered with dimples, all of which are ductile fractures.