Study On Laser Deposited Of TA15/Ti₂AlNb Gradient Composite Structure

TA15 has good comprehensive properties such as plasticity and thermal stability.It can work at 500? for a long time.Ti2AlNb has good specific strength,room temperature plasticity,fracture toughness and other characteristics.It can work for a long time at 650??850?.The composite structure of TA15 and Ti2AlNb can meet the requirements of aerospace parts working in different temperature environments.In this paper,the temperature field distribution of TA15/Ti2AlNb gradient composite structure prepared by laser deposition was simulated by finite element analysis.TA15/Ti2AlNb direct transition composite structure,TA15/Ti2AlNb gradient composite structure with 1 and 3 gradient layers were fabricated by laser deposition manufacturing technology.At the same time,the microstructure,tensile strength and microhardness of TA15/Ti2AlNb gradient composite structure were analyzed and studied.The results show that:through the simulation of temperature field distribution during the deposition process of TA15/Ti2AlNb direct transition composite structure,it is found that with the increase of deposition height,the maximum temperature value of center position of TA15 side and Ti2AlNb side gradually increases,while the transition interface node temperature decreases.The microstructure of TA15 side is composed of ? phases and ? phases.The transition interface is composed of ? phases,O phases,?2 phases,? phases and B2 phases.The pahse evolution of Ti2AlNb side is B2+O+?2?B2-O?B2.The transition interface is the weak position of TA15/Ti2AlNb direct transition composite structure.From the TA15 side to Ti2AlNb side,the microhardness decreases first,then increases before decreases,The microhardness of transition interface is not lower than that of TA15 side.Comparing the TA15/Ti2AlNb gradient composite structures with 0,1 and 3 layers,it can be found that with the increase of gradient layers,the temperature in the transition zone of TA15/Ti2AlNb gradient composite structure increases gradually,and the temperature gradient decreases gradually.The microstructure difference of each transition interface decreases gradually,and the microstructure on both sides of the transition zone is refined.With the number of gradient layers increaseing,the room temperature tensile strength of the TA15/Ti2AlNb gradient composite structure decreases,but the elongation after fracture increases.The fracture position occurs in the transition zone and gradually approaches to Ti2AlNb side.With the increase of the number of gradient layers,the difference of the transition interface weakens and the fluctuation of the microhardness in the transition zone decreases.