The Study On The Effect Of Pre-deformation And Heat-treatment On The Super-elastic Of NiTiCr Shape Memory Alloys

This article focuses on the effect of pre-deformation,solution treatment and aging treatment on the super-elastic of NiTiCr shape memory alloys.The test researches the effect of different pre-deformation on the super-elastic and microstructure of NiTiCr shape memory alloys through tensile test and the photos of NiTiCr metallographic structure.The test shows the super-elastic gets better with the growing of pre-deformation,while the deformation gets to 51.4%the growing rate gets slow.The pre-deformation can not make NiTiCr show entire non-line super-elastic.The pre-deformation would separate out a kind of fine and highly deformed martensite in NiTiCr.When the deformation gets to 48.6%,the martensite would grow with the growing of deformation,which increases the intensity of generatrix and the superelasticity of NiTiCr shape memory alloy.To enhance the using performance and the processing property,the article researches the super-elastic of NiTiCr shape memory alloys under different solution temperature by tensile test.The curves show that the elastic turns better with the increasing of solution time at lower temperature(720℃),but when the temperature of solution overrun 720℃the elastic is not increase any more.The samples show entire non-line super-elastic at 700℃and keeping warm for 60min then 430℃and keep warm for 20min.The sample can not show entire non-line super-elastic on other solution temperature.And the sample generate two inverse martensitic phase transformations and improve the stability of NiTiCr super-elastic under the solution treatment of 700℃and keeping warm for 60min.It also researches the super-elastic of NiTiCr shape memory alloys after aging treatment by WDW-10 Electronic Universal Testing Machines and D/max2500PC Automatic X-ray Diffraction(XRD) Machine.The test shows the effect of the different aging treatment temperature and the keeping warm time on NiTiCr super-elastic is marked.With the growing of temperature and keeping warm time,the elastic turn better first then weakness;When the temperature gets to 430℃and keeping warm time for 15～20min and 450℃and keeping warm time for 15 min,the samples take on non-line super-elastic entirely.The SEM photos proves that the sample would generate thermo-aeroelasiticity martensitic after aging treatment.With the over-growing of aging temperature,thermo-aeroelasiticity martensitic decrease,the super-elastic is upset.The XRD test proves that the sample would separate out a kind of strengthen phase named Ti₃Ni₄.The peak of this phase gets to maximum,then with the growing of temperature and keeping warm time it would get down.The super-elastic is the best at this condition.