利用光学显微镜(OM)、X射线衍射(XRD)、电子背散射衍射(EBSD)等方法, 对比研究了热轧和选区激光熔化(SLM)成形316L不锈钢水平面(X-Y面)和建造面(X-Z面)显微组织特征。结果表明, 两种方法制备的316L不锈钢均主要由奥氏体相组成。与轧制合金相比, SLM制备的316L不锈钢有着更多的低角度晶界和亚晶界, 位错密度更大。其中, SLM成形316L不锈钢X-Y面存在平行于(110)方向上的织构, X-Z面存在平行于(001)方向上的织构。X-Y面上晶粒取向偏离(001)方向, 可能与重熔过程中复杂的热流有关; X-Z面在(001)方向上存在织构且在(001)的织构指数最大, 这是因为在SLM成形过程中, 晶体的生长方式与建造方向平行, 且晶粒沿着(001)方向散热最快, 因此晶粒沿(001)方向呈择优生长。

The microstructure of cross sections (i.e. X-Y and X-Z), which are perpendicular to and parallel to the rolling or build-up directions for the hot rolled or selective laser melting (SLM) built 316L stainless steel blocks, respectively, was characterized by means of optical microscopy (OM), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). Results show that the 316L stainless steel prepared by the two methods mainly consists of austenitic phases. In comparison to the rolled 316L stainless steel, the SLM built 316L stainless steel has much more low angle grain boundaries and sub-grain boundaries, as well as higher dislocation density. It could be observed that the SLM-316L stainless steel shows a preferred texture parallel to (110) direction in X-Y plane and (001) direction in X-Z plane. The deviation of grain orientation from the (001) direction on the X-Y plane may be related to the complex heat flow during the laser remelting process. Texture is available in the (001) direction in the X-Z plane, and the texture index is the largest at (001), which is related that the crystals grow parallel to the build-up direction. Moreover, the heat dissipation is the heat fastest along the (001) direction during the SLM process; therefore, grains grow preferentially along (001) in shape of strips.