Structure And Properties Of Ti-V-Al Light Shape Memory Alloys Fabricated By Wire Arc Additive Manufacturing

Ti-V-Al shape memory alloy has low density and excellent cold working performance,and is a lightweight memory alloy with great potential.However,the current research on Ti-V-Al shape memory alloy is still focused on traditional melting and thermomechanical treatment,and the processing methods used are mostly subtractive processing,which cannot cope with the current preparation and processing of complex structural elements such as honeycomb in aerospace and other fields,and the reports of additive manufacturing of Ti-V-Al alloy are concentrated in structural materials,and there are few reports on the additive manufacturing of Ti-V-Al shape memory alloy.Therefore,three kinds of Ti-V-Al shape memory alloys with different V content were prepared by wire and arc additive manufacturing technology,and the microstructure evolution and properties of these alloys were systematically studied.It is found that with the increase of V content,the phase composition of Ti-V-Al shape memory alloy prepared by wire material and arc addition method will change significantly.The structure of Ti-12.2V-10.1Al alloy isα’martensitic phase+α"martensitic phase+a small amount ofβphase.With the increase of V content,theα’phase disappears and theβphase content continues to increase in the alloys.The structure of Ti-14.7V-9.8Al alloy is a large number ofα"+a small amount ofβphase,and the structure of Ti-17V-9.5Al is a small amount ofα"+a large number ofβphases.Theα"martensitic variants of the three wire and arc additive manufacturing Ti-V-Al alloys mainly have a self-collaborative relationship,and there is a{111}type I twin relationship in all three alloys,and a〈211〉type II twin relationship in Ti-14.7V-9.8Al alloy.At the same time,due to the different thermal environments of different regions of the same Ti-V-Al alloy during Wire and arc additive manufacturing process,the size of the martensitic variant in the alloy increases with the increase of the height of the deposited layer.In addition,the phase transition temperature of wire and arc additive manufacturing Ti-V-Al alloys prepared by decreased with the increase of V content,and when the alloy composition was Ti-17V-9.5Al,the phase transition temperature had dropped below room temperature.The phase transition temperature of different regions of the same wire and arc additive manufacturing Ti-V-Al alloys is also different,which is related to the fact that the phase transition temperature of the alloy is affected by the V content and internal stress.The hardness and strength of wire and arc additive manufacturing Ti-V-Al alloys decrease with the increase of V content,among which it is the highest in Ti-12.2V-10.1Al alloy,with a hardness of 326 HV_0.2and a tensile rupture strength of up to 905 Mpa.The elongation of the alloy increases first and then decreases with the increase of V content,and is the largest when the composition is Ti-14.7V-9.8Al,with an elongation of more than 9.0%.The strength of different regions of the same Wire and arc additive manufacturing Ti-V-Al alloy will change with the change of V content and phase composition,and the elongation of the bottom region is the best.In addition,the shape memory effect of wire and arc additive manufacturing Ti-V-Al alloys first increases and then decreases with the increase of V content,and the most excellent shape memory effect is obtained in Wire and arc additive manufacturing Ti-14.7V-9.8Al alloy,with a fully recoverable strain of 5.9%.In addition,in the same wire and arc additive manufacturing Ti-V-Al alloys,the shape memory effect of the alloy changes with the stress in different regions of the alloy.Among them,in Ti-12.2V-10.1Al and Ti-14.7V-9.8Al alloys,the recoverable strain decreases with the increase of the height of the sedimentary layer.In the Ti-17V-9.5Al alloy,the recoverable strain in the middle region is maximum.