Numerical Simulation And Microstructure Evolution For Hot Rolling Process Of Ti-43Al-9V-Y Alloy

The hot deformability of TiAl alloy is poor, Expecially for hot rolling process. So itis difficult to prepare TiAl sheets with both excellent microstructure and mechanicalproperties. Because of the softer phase, the beta-gamma TiAl alloy can largely improvethe hot deformability, but the intensity is still limitied. This paper selected theTi-43Al-9V-Y alloy, and investigated its hot rolling process using thermal-mechanicalcoupled finite element simulation, microstructure evolution for different temperature ofquenching and rolling passes.This paper used ABAQUS/Explicit to study the hot rolling process.Based on theactual rolling process; we determined the thermal-mechanical boundary condition tomake sure the establishment of a reliable finite element model. Based on this model, thetransfer process was investigated by using thermal-mechanical coupled finite elementsimulation. Results showed that: the introduction of the pack could gratedly improveuniformity of temperature distribulation.with the increment of the thickness of the pack,heat loss of the TiAl sheet was more less.The introduction of the insulation layer wastaken a step forward to improve the uniformity of temperature distribution. Thermalconductivity of the TC4titanium alloy was smaller than the304stainless steel.Simulation results showed that insulation effect of the TC4titanium alloy was betterthan insulation effect of304stainless steel. Structures of the workpiece were as follows:304stainless steel or TC4titanium alloy as the material of the pack;5mm,9mm or13mm as the thickness of the pack; silica fabric as the insulation layer.Based on the orthogonal experimental design, different parameters combition ofpack rolling were simulated. Results of the temperature distribution, effective stress andeffective strain were obtained. Larger deformation would be obtained through TC4titanium pack-rolling. Resistance to deformation between304stainless steel andTi-43Al-9V-Y matched well. By comparision, the most excellent parameters were asfollows:304stainless steel can,9mm can thickness,1200℃deformation temperatureand0.3m/s rolling speed.Simulaiton results were verified by the experiment, sheet without pack-rollingshowed rough surface and serious cracking, sheet with pack-rolling had smooth surfaceand no cracking. The microstructure of the rolled Ti-43Al-9V-Y alloy showedtwo-phase structure: γ phase and β/B₂phase. The mount of precipitated lath-shaped γphase from B₂phase without pack-rolling was more than that of with pack-rolling,meanwhile the grain size of the β/B₂phase was bigger. Deformation behavior in hightemperature was poor. With the increase of the rolling pass, the amunt of precipitatedlath-shaped phase from B₂phase was increase. The distribution of RE-riched phase was more homogeneous and more disperse. Micro-cracks in γ phase disapperred gradually.Quenching experiments of Ti-43Al-9V-Y alloy showed the evolution ofmicrostructure. With the incrementment of the temperature, the amount of α/α₂phasegradually reduced, the amount of β/B₂gradually increased. The enhancement ofdeformation temperature can improve deformation behavior of Ti-43Al-9V-Y alloy.