Martensitic Transformation And Mechanical Behavior Of Multiphase Ti-V-Al Shape Memory Alloys

Ti-V-Al alloy is a kind of shape memory alloy with great potential in aerospace.When the composite structure is connected in the weapon equipment,because of the low modulus of elasticity of Ti-V-Al shape memory alloy the connection failure problem is easy to occur.Based on the idea of composite materials,the reinforcements is introduced into the Ti-13V-3Al alloy by in-situ method to improve the elastic modulus and yield strength of the alloy.Microstructure,martensitic transformation,thermal cycling stability,mechanical properties and shape memory effect of multiphase Ti-V-Al shape memory alloy with different reinforcements types and different volume fraction of reinforcements were systematically studied.By thermodynamic calculation,it can be concluded that the reinforcements introduced by Ti-TiB₂ mode is TiB.And the reinforcements introduced in Ti-TiB₂ mode are TiB and TiC.The room temperature microstructures of the solid solution multiphase Ti-V-Al shape memory alloys are ?" martensite and reinforcements.The introduction of the reinforcement makes the alloy grain finer and has no effect on the chemical composition of the matrix alloy.In the alloy,TiB is mostly fibrous and partly granulated.TiC is granulated in the alloy.With the increase of volume fraction of reinforcement,the number and size of TiC increase,and the number of granular TiB increases.With the introduction of the reinforcements,the martensitic inverse phase transition temperature of multiphase Ti-V-Al shape memory alloy increases.The introduction of reinforcements can improve the thermal stability of alloy.With the increase of volume fraction of reinforcements,the martensitic inverse phase transition temperature of alloy increases.The addition of reinforcements in Ti-B4 C mode can improve the thermal stability of alloy better than that in Ti-TiB₂ mode.When the volume fraction of the reinforcements reaches 0.5%,the martensitic thermal stability of the alloy is the best.When the volume fraction of reinforcments reaches 0.5%,the strengthening effect of TiB and TiC as reinforcements was better than that of TiB as the single reinforcements.With the increase of volume fraction of reinforcements,the elongation of alloy decreases gradually,and the modulus of elasticity and yield increase gradually,and the tensile strength increases first and then decreases.When the volume fraction of the reinforcements is 0.5%,the comprehensive mechanical property of the alloy is the best.With the increase of volume fraction of reinforcement,the memory effect of alloy increases first and then decreases,and reaches maximum when volume fraction of reinforcements is 1%.