Study On Hrat Treatment Process Of Laser Deposition TA15/Ti₂AlNb Gradient Composite

In recent years,gradient composites have been increasingly used in high-tech fields.Laser deposition manufacturing has significant advantages in the fabrication of composite materials.In this paper,TA15/Ti2AlNb direct transition and gradient composite structure samples were prepared by LDM technology,and a variety of heat treatments were carried out on the samples.The changes of microstructure and mechanical properties of the samples were analyzed,and the ways to improve the comprehensive properties of the alloy composite were explored,which provided reference for the design of new aerospace structures.The results show that the microstructure of TA15/Ti2AlNb transition interface is improved effectively by heat treatment,and the microstructure on both sides becomes more uniform,and the tensile strength and microhardness of the samples are not significantly reduced,while the plasticity is significantly improved,which makes it have better comprehensive properties,but the transition interface is relatively weak.The effects of different cooling methods on the microstructure and properties of TA15/Ti2AlNb after annealing heat treatment show that the microstructures of furnace cooling and air cooling are similar,martensite ?' phases appear in TA15 side after oil cooling,and the microstructure of TA15 side after water cooling is relatively fine and evenly distributed.The volume fraction of O phases in Ti2AlNb side decreases after oil cooling and water cooling.The higher the cooling rate is,the higher the microhardness of TA15 side structure is.After water cooling,the highest microhardness of TA15 side reaches 503.2 HV0.2,while the cooling rate has little effect on the microhardness of Ti2AlNb side.Gradient structure can effectively improve the comprehensive mechanical properties of the TA15/Ti2AlNb gradient composite structure samples,the properties of the transition region of the gradient composite are no longer weak,and the comprehensive properties of the samples with three-layer transition zone are better than those of one-layer samples.The properties of annealed samples are better than those of as-deposite and solution and aging samples.The tensile strength and elongation after fracture of TA15/Ti2AlNb composite with three transition layers are 909.27MPa and 6.73%respectively after annealing at 900?×1h for 1 hour.With the increase of Ti2AlNb alloy content,the microhardness of each transition layer increases before decreases.The hardness of each transition layer of as-deposite sample is relatively high,which is 462.1 HV0.2,470.5 HV0.2 and 457.6 HV0.2 respectively.