选区激光熔化IN718合金室温及高温拉伸性能研究

Room and Elevated Temperature Tensile Properties of IN718 Alloy Fabricated by Selective Laser Melting

采用选区激光熔化技术制备了IN718合金,对其凝固组织形成机制和热处理固态相变行为进行了研究,分析了IN718合金经热处理后的室温和高温拉伸断裂机理。研究结果表明,选区激光熔化IN718合金沉积态显微组织为沿沉积增高方向定向生长的树枝晶,枝晶间分布着纳米级Laves相。经标准热处理后晶粒形态没有明显变化,大量γ′和γ′′相以及针状δ相弥散析出,Laves相含量减少,合金硬度较沉积态高约40%。经热处理后,合金垂直于沉积增高方向试样抗拉强度高于锻件,平行于沉积增高方向的试样塑性优于锻件,高温拉伸强度与锻件相当,室温及高温拉伸断裂机制均为微孔聚集型的穿晶韧性断裂。

The IN718 alloys were fabricated by selective laser melting forming technique.The formation mechanism of solidi-fication structure and the behavior of phase transformation during heat treatment were investigated.The tensile fracture mechanism of IN718 alloy at room and high temperature after heat treatment was analyzed.The results show that the microstructure of sample is dendrite along building direction.Nanoscale Laves phase is distributed among the dendrites.The grain morphology has no obvious change after standard heat treatment.A large number ofγ′,γ′′and acicularδphase dispersive precipitate.The content of Laves phase decreases and the hardness is about 40%higher than as-deposited samples.After heat treatment,the tensile strength of samples perpendicular to the building direction is higher than forgings.The plasticity of samples parallel to the building direction is better than forgings.The tensile strength is comparable to forgings at high temperature.The fracture mechanism of selective laser melted IN718 alloy after heat treatment is a through-granular ductile fracture mode of micropore aggregation.