Effect of heat input on austenite microstructural evolution of simulated heat affected zone in 2205 duplex stainless steel
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The effect of simulated welding thermal cycle on the microstructure and impact toughness of heat affected zone (HAZ) in 2205 duplex stainless steel was investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy and room temperature impact test. The results show that the morphology and volume fraction of austenite change greatly with heat input. The amount of residual austenite and grain boundary austenite (GBA) decreases while Widmanstätten austenite (WA) laths and intergranular austenite increase with the increase in heat input. Only the fine equiaxed austenite exists in the HAZ when the heat input is increased up to 61.8 kJ/cm. WA laths nucleate initially either at the ferrite and GBA phase boundaries or directly in ferrite grains and begin to decompose into diamond-shaped austenite with the heat input larger than 25.2 kJ/cm. The impact toughness shows a non-monotonic variation, which is related to the increase in austenite fraction and the formation and the decomposition of WA laths.
Keywords2205 duplex stainless steel Simulated heat affected zone Heat input Widmanstätten austenite Impact toughness
The authors gratefully appreciate the financial support by the National Natural Science Foundation of China (Grant No. 51471048 and No. U1860201), the Basic Research Program of Key Laboratory of Liaoning Province (LZ2015035) and the Fundamental Research Funds for the Central Universities (N140206001 and L1502045).