铸造镍基高温合金K417G中高温拉伸断裂机理研究OACSTPCD

The fracture mechanism of the K417G high-temperature alloy under tensile conditions at 700℃and 950℃after hot isostatic pressing heat treatment was studied.Tensile tests at elevated temperatures were conducted using a universal testing machine,and observations of microstructures,fracture surfaces,and longitudinal sections were carried out through scanning electron microscopy.The results reveal that the dendritic morphology of the samples after heat treatment is pronounced,with a high degree of cuboidal γ'phase on the dendrite branches,measuring 0.4-0.5 μm and arranged in an orderly fashion.Petal-shaped γ'phase with sizes ranging from 1.5-2.6 μm precipitates between the dendrites.Comparing the tensile properties of samples at 950℃to those at 700℃,the tensile strength decreases by 46.3%,while the elongation increases by 200%.This indicates a reduction in high-temperature tensile strength and an increase in plasticity.During moderate-temperature tensile testing,elongated carbides between the dendrites serve as the primary crack initiation and propagation paths.In contrast,during high-temperature tensile testing,carbides at grain boundaries and eutectic constituents act as crack initiation sources,with cracks propagating along grain boundaries,forming a transgranular fracture morphology.