后处理对激光沉积CoCrNiMo0.0136中熵合金组织与性能的影响

为了研究后处理对CoCrNi中熵合金组织与性能的影响规律和机理, 采用激光增材技术制备了Co_0.3288-Cr_0.3288-Ni_0.3288-Mo_0.0136中熵合金。利用光学显微镜、扫描电子显微镜、X射线衍射仪、电子背散射衍射、3维表面形貌仪和万能拉伸试验机对CoCrNiMo_0.0136中熵合金激光沉积态、热锻态和热锻喷砂态3种状态下的合金组织和性能进行了表征。结果表明, 激光沉积CoCrNiMo_0.0136中熵合金在沉积态、热锻及热锻喷砂处理后均具有稳定的面心立方结构, 沉积态下, 合金的晶粒粗大, 因为微观偏析, 晶内存在元素分布不均的亚结构, 合金强度较低, 但塑性良好; 热锻处理后, 合金晶粒显著细化, 可以观察到较多的退火孪晶, 较激光沉积态, 屈服强度提高132.88%, 抗拉强度提高53.78%, 延伸率无明显变化; 热锻试样经喷砂处理后, 试样表面出现梯度纳米结构, 其厚度约为100μm, 塑性变形层中存在大量纳米孪晶, 此时合金具有良好的综合力学性能, 较激光沉积态, 屈服强度、抗拉强度分别提高220.09%和96.22%, 延伸率无显著变化。该研究通过热塑性加工及制备纳米梯度表面结构, 可有效提升Mo掺杂CoCrNi中熵合金静力学性能。

Study on the effect on microstructure and properties of CoCrNiMo0.0136 medium-entropy alloy in laser deposited by post-treatment

In order to study the effect and mechanism of post-treatment on the microstructure and properties of medium entropy alloy in CoCrNi, the medium-entropy alloy in Co_0.3288-Cr_0.3288-Ni_0.3288-Mo_0.0136 was prepared by laser deposition. The microstructure and properties of medium-entropy alloy in CoCrNiMo_0.0136 under laser deposition, hot forging and hot forging sandblasting were characterized by optical microscope, scanning electron microscope, X-ray diffractometer, electron backscatter diffraction, 3-D surface profilometer, and universal tensile testing machine. The results show that the medium-entropy alloy in laser deposited CoCrNiMo_0.0136 has stable face-centered cubic structure after as-deposited, hot-forging, and hot-forging sandblasting. In the deposited state, the grain size of alloy is coarse, because of microsegregation, there is a substructure with uneven distribution of elements in the grain, and the strength of the alloy is low, but the plasticity is good. After hot forging treatment, the grain size of alloy is significantly refined, and more annealing twins can be observed. Compared with the laser deposited state, the yield strength is increased by 132.88%, the tensile strength is increased by 53.78%, and the elongation has no obvious change. After the hot forging sample was sandblasted, the surface of the sample showed a gradient nanostructure with a thickness of about 100μm, and there were a large number of nano-twins in the plastic deformation layer, the yield strength and tensile strength increased by 220.09% and 96.22% respectively, and the elongation did not change significantly. Through thermoplastic processing and preparation of nano-gradient surface structure, the static properties of medium-entropy alloy in Mo-doped CoCrNi can be effectively improved.