Effects of solution treatment on microstructure and tensile properties of as-cast alloy 625

Abstract

Effects of solution treatment between 1050 and 1250 °C on microstructure and tensile properties of as-cast alloy 625 were investigated. The microstructure and solidification characteristics of the alloy were studied by SEM, EDS, EPMA and DTA. The results showed that the solidification sequence of the alloy should be written as L → L + γ → L + γ +MC→ L + γ +MC+ γ /Laves→ γ +MC+ γ /Laves. After solution treatment at 1225 and 1250 °C, incipient melting of Laves phase was observed. The ultimate tensile strength decreased monotonically with the increase of solution treatment temperature, and the yield strength had no significant variation. The elongation increased slightly at first and then reached a minimum value at 1250 °C. The fracture mechanism changed from transgranular mode to intergranular mode after solution at 1250 °C for the reason that numerous Laves phases melted at grain boundaries and microcracks nucleated in the molten pool. The suitable solution treatment temperature of this alloy was 1200 °C.