时效处理对激光立体成形17-4PH不锈钢组织及性能的影响

Influence of Aging Treatment on the Microstructure and Properties of 17-4PH Alloy by Laser Rapid Forming

研究了时效热处理对激光立体成形17-4PH(0Cr17Ni4Cu4Nb)沉淀硬化不锈钢组织及力学性能的影响。光学显微镜(OM)和扫描电子显微镜(SEM)观测结果表明,经过时效热处理后,激光立体成形17-4PH不锈钢的微观组织主要由淬火马氏体、回火马氏体和第二相强化质点组成。随着时效温度的升高,构成基体的马氏体板条变得更加细小均匀,淬火马氏体向回火马氏体的转变增多,且板条间的第二相质点逐渐粗化,数量逐渐增多;晶界变得更加清晰、细长。热处理后材料的塑性比沉积态有显著的提高。480℃时效处理时,材料的强度、硬度达到最大值;随着时效温度的升高,材料的强度、硬度逐渐降低,塑性逐渐提高。热处理后试样的拉伸断口均呈现韧性断裂特征,并且随着时效温度的升高,纤维区和剪切唇越来越大,韧窝尺寸及深度逐渐增大。

Influence of heat treatment on microstructures and properties of 17-PH alloy by laser solid forming （LSF） process is investigated. Results of optic microscope （OM） and scanning electron microscope （SEM） show that main microstructure of LSF 17-4PH includes quenched martensite, tempered martensite and second precipitated phase. As aging temperature increases, martensite becomes smaller and more uniform, Rate of transformation from quenched martensite to tempered martensite is accelerated. Precipitated phases begin to coarsen, grain boundary becomes distinct. After heat-treatment, alloy plasticity is highly improved, and the strength and hardness reach maximum when aging temperature is 480℃. With the aging temperature increasing, strength property and hardness get worse, while plastic property gets better. Analysis on fractography shows fracture of all tensile samples results from ductile fracture. In addition, fiber area and shear lip of fracture become bigger, and size and depth of dimples increase gradually with the aging temperature increasing.