Microstructure And Shape Memory Effect Of Cold Rolled Ti-V-Al-Zr Shape Memory Alloy

With the deep exploration of space by human beings,the challenges faced by spacecraft will become more severe.In order to cope with the unknown environment for exploring space,how can various aviation and space vehicles as vehicles carry as much equipment as possible to deal with the unknown.Therefore,spacecraft for exploring space has higher requirements,and the lightweight of spacecraft has become an inevitable problem.In addition to improvements in aircraft design,weight reduction of materials is also an important means of making spacecraft lightweight.Ti–V–Al alloy is a great candidate for a lightweight SMA.Firstly,it has a low density,which,at about4.5 g cm3,is close to that of pure titanium.That is lower than the densities of other SMAs.Ti–V–Al alloy has a great cold workability of over 90%thickness reduction during cold rolling,which makes it easy and inexpensive to process into different shapes.Spacecraft composite with metal part fastener is a one major application of memory alloy in aerospace.This fastener usually represented by aircraft tube joints.But currently Ti–V–Al alloys is not used in these joints due theirs relatively small for this application yield strength about 300 MPa.The effects of Zr content on martensitic transformation and shape memory effect of Ti–V–Al alloys is not studied.The aim of this research is by addition of Zr?0.5%,1.0%,2.0%?increase yield strength of shape memory material and to approach application of Ti–V–Al alloys in this kind of joints.The room temperature structure of solid solution Ti-V-Al alloy change with the increase of Zr content.The room temperature structure of?Ti-13V-3Al?_100-x00-x Zr_x?X=0.5,1?alloy?is?cubic structure with some amount of martensite,mainly it consist of betta phase.The orthogonal structure of?"martensite phase,martensite variants show a self-cooperative relationship,mainly?111?type twins.The athermal?phase formed during quenching in?Ti-13V-3Al?_100-xZr_x?X=0.5?alloy.The?Ti-13V-3Al?_100-x00-x Zr_x?X=2.0?alloy consists of only betta phase or just small amount of martensite,which could not be found during the microscopic observations.Zr doping can significantly decrease the size of grains.There is a precipitation of second phase on surface of polished samples of the Ti-13V-3Al alloys with Zr doping content of 2.0%.With the increase of Zr content,the martensite inversion temperature As,Ap and Af of solid solution Ti-V-Al-Zr alloy decrease gradually.With the increase of Zr content,the elongation and tensile strength of solid solution and as-cast Ti-V-Al-Zr alloys first increase and then decrease.When the sample is doped with Zr of 1%atomic ratio,the elongation of the alloy increases to maximum value 14.1%.With the content with Zr content of 2.0 at.%,the elongation of the alloy reaches its minimum value,the minimum elongation is10.2%.With the increase of Zr content,the yield strength and maximum tensile increase.The yield strength and tensile strength?Ti-13V-3Al?_100-x00-x Zr_x?X=0.5?alloy are the smallest,reaching the strength 295 MPa and 640 MPa respectively.The yield strength and tensile strength of?Ti-13V-3Al?_100-x00-x Zr_x?X=2?alloy with minimum elongation are largest,reaching the maximum tensile strength and yield strength that are 540 MPa and 790 MPa respectively.Improvement in tensile strength ascribed to precipitation strengthening.Insoluble Zr in the matrix agglomerates at the grain boundary causes embrittlement failure.