Microstructure and mechanical properties of thermal simulation welding heat-affected zone of Ti2AlNb alloy
Ti2AlNb alloys are promising candidate materials for advanced aviation engine hot end components due to their high specific strength and high-temperature oxidation resistance.But as an intermetallic compound materials,their weldability is a challenging issue.To understand the influence of welding thermal cycling on the microstructure and properties of the alloy,the Gleeble3500 thermal simulation testing machine was used to simulate the thermal cycling in the heat affected zone near the weld of the Ti2AlNb alloy,and the effect of cooling rate on the microstructure and properties of the welding heat affected zone was studied.Based on the thermal expansion-temperature curves and the microstructure of the alloy at different cooling rates,the simulated HAZ continuous cooling transformation(SH-CCT)curves for the welding heat affected zone of the Ti2AlNb alloy were established.The results show that during the continuous cooling process after rapid heating to the B2 single-phase zone,the main precipitate in the Ti2AlNb alloy is O phase,the precipitation amount of α2 phase is very small.As the cooling rate increases,the number and size of precipitates gradually decrease,and the precipitation of α2 phase is first suppressed,and the transformation from B2 to O phase is completed within a narrower temperature range.Low cooling rate,large number of precipitates in the alloy,high strength,but low plasticity.On the contrary,with the increase of cooling rate,the residual B2 phase increases,and the plasticity of the alloy is improved.
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