Researches On Plane Strain Deformation Behavior And Microstructure-Property Relationship Of TC21G Titanium Alloy

In recent years,with the change of maritime defense policy of China,higher performance requirements have been put forward for naval equipment,such as ships and submarines.Meanwhile,the application of titanium alloy in naval equipment has also been promoted.As a kind of damage tolerance of titanium alloy with high strength and high toughness,TC21 titanium alloy has been successfully used in aerospace structural components manufacturing.In order to obtain the modified alloy suitable for application in ships,based on the TC21 titanium alloy,the modified alloy was designed.In this paper,the relationship between microstructure and mechanical properties of TC21G titanium alloy was systemically studied,and it is of great significance for manufacturing the marine material.The hot deformation behavior in plane strain compression of the TC21G titanium alloy was investigated in the deformation temperatures ranging from 870℃ to 940℃,the strain rates ranging from 0.1s-1 to 1s-1.The evolution of microstructures was also analyzed.Meanwhile,the effect of processing parameters on the strain hardening exponent n was analyzed.The results show that in the condition of a certain strain rate,the flow stress of alloy decreases with the increasing of deformation temperature due to the increasing of β phase content.However,in the condition of a certain temperature,the flow stress of alloy increased with the increasing of strain rate.During deforming in the α+β field,the globularization degree of the lamellar a phase increased with the increasing of deformation temperature or strain.The variation of n values was found to depend on the dynamic recrystallization(DRX),dynamic recovery(DRV)of a and β phases.In this paper,the effects of solution temperature,aging temperature and cooling rate on a phase morphology,size and content of TC21G titanium alloy were studied respectively.Based on the study,it was found that with the increase of the solution temperature,the content of lamellar and equiaxed a phase decreased;with the increase of the aging temperature,the size and content of fine acicular secondary a phase increased;with the decrease of the cooling rate after solution treatment,the size of equiaxed a phase and lamellar a phase was obviously coarsened,and the content of secondary a phase was decreased,while the size of fine acicular secondary a phase was increased.Meanwhile,with the decrease of the cooling rate,the volume fraction of high angle grain boundary of α grains increased.The relationship between heat treatment process parameters,microstructures and mechanical properties was studied.It was found that with the increase of the solution temperature,the strength increased and the plasticity decreased.The strength of the TC21G titanium alloy was significantly increased after aging treatment.Increasing aging temperature will lead to the decrease of the strength for alloy.In this study,the most appropriate aging temperature is 590℃.With the decrease of the cooling rate after solution treatment,the strength of the alloy decreased,while the plasticity increased.The impact toughness of TC21G titanium alloy can be improved by increasing the content of staggered lamellar a phase,decreasing the cooling rate or decreasing the solution treatment temperature.When the alloy is heat treated at 910℃/1h/FC+590℃/4h/AC,the mechanical property with excellent impact toughness of 53 J/cm2 can be obtained.