Study On The Properties Of Ti-6Al-4v+xY₂O₃ Alloy Prepared By Spark Plasma Sintering And Metal Injection Molding

Metal Injection Molding(MIM)can produce small and medium-sized parts with complex geometry in large batch and near net shape without significantly increasing the cost,but its experimental process is much and time-consuming,so it is not suitable for large-scale test of new material development and design.Spark Plasma Sintering(SPS)is widely used in the development and composition design of new materials because of its advantages such as short experimental process and controllable structure.Therefore,in this experiment,the composition of Ti-6Al-4V alloy and rare earth Y₂O₃ were designed by SPS,and the influence of micro/nano Y₂O₃ on the microstructure and mechanical properties of Ti-6Al-4V alloy was explored;then Ti-6Al-4V+x Y₂O₃ alloy was prepared by MIM according to the optimization results of SPS.In the composition design of SPS,the effect of Y₂O₃ particle size and content(0%,0.2%,0.4%,0.6%,0.8%)on the microstructure and mechanical properties of Ti-6Al-4V alloy was investigated.The results show that the microstructure of the alloy is widmanstatten structure when Y₂O₃ is added,and the grain size of Ti-6Al-4V alloy can be refined when 0.2%is added.Through the compression test of Ti-6Al-4V+micron Y₂O₃ alloy,it is found that when the content of micron Y₂O₃ is 0.8%,the compression performance of the alloy is the best,and the compressive strength,yield strength and deformation are 1852 MPa,970 MPa and 28.9%,respectively.Compared with no Y₂O₃,the compressive strength and yield strength increased by 14.1%and 7.8%respectively.With the increase of Y₂O₃ content,the average grain size of Ti-6Al-4V alloy decreases with the increase of Y₂O₃ content.When Y₂O₃ content is 0.8%,the grain size can reach33?m.When Y₂O₃ content is more than 0.6%,Y₂O₃ nanoparticles begin to precipitate at the grain boundary.When Y₂O₃ content is 0.6%,the compressive strength,yield strength and deformation are 1158 MPa and 1974 MPa respectively.The yield strength and compressive strength increased by 13.5%and 24%respectively,and the deformation increased from 24.8%to 33%compared with those of no Y₂O₃.The Ti-6Al-4V+micro Y₂O₃ alloy and Ti-6Al-4V+nano Y₂O₃ alloy were optimized by SPS method.The Ti-6Al-4V alloy was prepared by adding 0.6%nano Y₂O₃.The binder formula was POM:HDPE:EVA:PW:SA=86:5:5:2:2.In the process of MIM degreasing,the influence of powder loading on the degreasing rate was compared.It was found that the degreasing rate of green billets was 88.4%at56%powder loading and 86.1%at 60%loading.The effect of sintering temperature on the mechanical properties of the alloy was studied.The results show that the densification and mechanical properties of the samples increase with the increase of sintering temperature at 1170??1280?.The best mechanical properties at 1280?are 60%powder loading,94.82%densification,872 MPa tensile strength,2.0%elongation and1550 MPa bending strength.