Study On Constitutive Relationship And Deformation Microstructure Of Ti40Alloy

Ti40alloy is a single beta phase burn resistant titanium alloy. It possesses betterburn resistant and mechanical properties. In this paper, the influence ofthermomechanical parameter on flow stress and microstructure of the as-cast alloyTi40was studied, and constitutive relationship for this alloy was constructed byisothermal and constant strain rate compression tests. The studied results have greatguidance significance for improving accuracy in plasticity processing of Ti40alloy byfinite element simulation and making reasonable hot working process. The mainresearch results are as follows.The flow stress of the as-cast alloy Ti40decreases with increasing temperaturesand decreasing strain rates. The sensitivity of flow stress to temperatures and strainrates at high strain rate is higher than that at low strain rate. The stress-stain curves aremainly type of steady-state. For the as-cast alloy Ti40, because the relationshipsbetween f (σ)with ln ε&and1/T are not bilinear, the constitutive equation can notbe directly constructed in accordance with equation of Arrhenius type. On the base ofthe equation of Arrhenius type, the constitutive model for the as-cast alloy Ti40ispresented. By using the experimental data, the coefficient of constitutive model isobtained by regression, and the constitutive equation is constructed. Error analysisindicated that the difference between the calculated and experimental flow stress isapproximately within10%. The constructed constitutive relationship is completely tomeet error requirement in the field of plastic processing.At different strain rate when high compression rate is60%, the temperature atwhich dynamic recrystallization occurred expanded from high temperature to lowtemperature with decreasing strain rates. At different temperature when highcompression rate is60%, the strain rate at which dynamic recrystallization occurredexpanded from low strain rate to high strain rate with decreasing temperature.Dynamic recrystallization grains mainly appear in primitive beta grain boundary,which expand to intransgranular with increasing temperatures or decreasing strain rates.At different strain rate or temperature, with increasing temperatures or decreasingstrain rates, the volume fraction and average grain size of dynamic recrystallization grains are mainly increasing. In view of reducing energy consumption and improvingprocessability, the preferable strain rate is below0.1s-1in the temperature range of950℃～1000℃, and below1.0s-1at1050℃, and in the range of0.001s-1～1.0s-1at1100℃.In all temperatures and strain rates, when strain is less than0.11, dynamicrecrystallization does not occur. When strain is equal to0.11, dynamic recrystallizationoccurs in the temperature range of1000℃～1100℃. When strain is higher than andequal to0.22, dynamic recrystallization occurs in lower strain rate in the temperaturerange of950℃～1000℃, and dynamic recrystallization occurs below1.0s-1at thetemperature of1050℃, and dynamic recrystallization occurs in the range of0.001s-1～1.0s-1at the temperature of1100℃. When temperature is constant with decreasingstrain rates or When strain rate is constant with increasing temperatures, the volumefraction and average grain size of dynamic recrystallization grains generally increase atthe same strain.