Heat Treatment Microstructure and Tensile Properties of Laser Additive Repaired K4169 Alloy
The high quality repair of K4169 alloy substrate was carried out by using laser additive repair.The effects of homogenization treatment+solution treatment+two-stage aging treatment(SIDA)on the microstructure and tensile properties of the laser additive repaired K4169 alloy were studied.The research shows that the repair morphology of the laser additive repaired K4169 alloy is good,and no defects are detected by penetration testing and X-ray testing.The repaired microstructure is a typical coarse columnar dendrite epitaxially grown along the deposition direction,and a large number of fine needle-like Laves phases precipitate between dendrites.After SIDA heat treatment,the stable columnar dendrite structure through each repair layer is transformed into fine equiaxed grains,the brittle phase Laves phase is obviously melted,showing fragmentation.The average tensile strength of the repaired sample is 521 MPa,which reaches 856 MPa after SIDA treatment,which is higher than 825 MPa of the casting,but the elongation decreases from 31.4%of the repair state to 20.3%,which is still higher than 5%of the casting.The fracture positions of all tensile specimens at room temperature are in the heat affected zone and they are ductile fracture.
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