【摘要】 选区激光熔化成形的TC4合金断裂韧性较差，低周疲劳性能较低，各向异性明显。采用循环退火（700～950℃）和固溶时效相结合的方法对TC4成形件进行热处理，利用光学显微镜、扫描电子显微镜、低周疲劳试验机等手段研究热处理对SLM TC4成形件显微组织和力学性能的影响。研究表明，SLM TC4微观组织由马氏体α′和马氏体α″组成，断裂韧性值为36.4 MPa·m^0.5，断裂韧性各向异性达25.7%；热处理后部分板条α相分解，产生等轴α相和二次α相；经过700～950℃循环5次后固溶+550℃时效后SLM TC4的断裂韧性值为96.0 MPa·m^0.5，断裂韧性的各向异性为1.4%。通过比较热处理样件和锻件低周疲劳性能得出结论，当应变幅≥0.9%时，热处理件低周疲劳性能高于锻件；当应变幅≤1%时，920℃循环退火+550℃固溶时效的低周疲劳性能高于920℃循环退火。更多还原

【Abstract】 The TC4 samples formed by selective laser melting（SLM） have poor fracture toughness,low cycle fatigue performance and obvious anisotropy.The TC4 samples were treated by the combination of cyclic annealing（at 700–950 ℃ respectively） and solid solution aging.The effects of heat treatment on the microstructure and mechanical properties of the TC4 samples were studied by optical microscope,scanning electron microscope and low cycle fatigue testing machine.The microstructure of SLM TC4 sample is composed of martensite α′ and martensite α″,the average value of fracture toughness is 36.4 MPa·m^0.5,and the anisotropy of fracture toughness is 25.7%.After heat treatment,αlath is separated from each other,equiaxed α phase and secondary α phase are formed.The fracture toughness of SLM TC4 is 96.0 MPa·m^0.5 after cyclic annealing at 700–950 ℃ and aging at 550 ℃,and the anisotropy of fracture toughness is 1.4%.Compared with the forged samples,the heat treated SLM sample exhibits better low cycle fatigue performance when the strain amplitude is greater than or equal to 0.9%;When the strain amplitude is less than 1%,the low cycle fatigue performance of the SLM sample produced by cyclic annealing at 920 ℃ and solid solution aging at 550 ℃ is higher than that produced by cyclic annealing at 920 ℃.更多还原