Study On The Microstructure And Mechanical Property Of TiAl-based Metal Composites Fabricated By Selective Laser Melting

Titanium aluminum?TiAl?-based alloys has excellent high temperature performance,such as low density,good heat resistance,high specific strength,good oxidation resistance and high temperature creep property.It is considered to be an ideal material for future applications of light structural components in aerospace and automotive industry.However,due to the brittleness and poor thermal deformability of TiAl alloy,the parts manufactured by traditional technology are easy to crack,and cannot form the complex structure parts with excellent performance.Without the using of tools and dies,Selective Laser Melting?SLM?can directly melting the TiAl alloy powder to process the parts with complex structure under the action of high energy laser beam,and the manufacturing speed is fast,so short the product development cycle,it is suitable for forming the complex components in the field of Aeronautics and Astronautics.Compared with the traditional manufacturing process,the rapid melting of metal powders and rapid cooling of molten pool in SLM forming process,so the parts processed by SLM are quiet different from the parts fabricated by the traditional methods in microstructure and mechanical properties.In this paper,TiAl-based metal powder materials were prepared with Ti-48Al-2Cr-2Nb as matrix powder,and the process,microstructure and mechanical properties of TiAl-based alloys formed by SLM were studied.The paper research the forming process,microstructure and mechanical properties of TiAl-based metal powder processed by SLM.The main contents are as follows:?1?TiAl-based metal composite powder had been processed by SLM,and the influence of the laser scan line spacing on grains characteristic,crystallographic texture,phase transition and nanohardness of the SLM-processed samples had been systematic investigated.The study found that in the Ti-48Al-2Cr-2Nb/RGO alloy formed by SLM,with the increase of the laser scan line spacing,the grains of the SLM-processed samples gradually refined,while their grains orientations with a combination of?0001?,?101?1?and?112?1?directions basically remain unchanged.The content of high-angle grain boundaries?HAGBs?decreased with the increase of the laser scan line spacing.The parts fabricated by SLM mainly consist of?₂,?and B₂ phases.With increasing the laser scan line spacing,the content of?₂ phase decreased while the contents of?and B₂ increased.The nanohardness and Young's modulus respectively increased from 8.13±0.392 GPa and 155.62±7.78 GPa to 9.85±0.458 GPa and 179.02±8.90 GPa when increasing the laser scan line spacing.?2?The microstructure evolution and mechanical properties of SLM-processed TiAl/B parts with varied B content were systematically discussed.And found that the average grain size of SLM-processed TiAl/B parts significant refined from 16.64?m to 5.66?m when the content of B element increased from 0 to 2 wt%,in addition,the crystallographic orientations transformed from a strong?101?1?and?112?1?orientations to a dominated?0001?orientation.With increasing the content of B element from 0 to 1 wt%,the{0001}texture index of SLM-processed TiAl/B parts increased from 10.78 to 22.69,and the HAGBs increased from 87.9%to 94.4%.The compressive strength and strain respectively increased from 1083.16 MPa and 3.43%to 1610.53 MPa and 5.17%when the content of B element increased from 0 to 2 wt%.And the failure mode is typical brittleness fracture.In this paper,the research results of microstructure and mechanical properties of the TiAl matrix composites parts processed by SLM provide a basis theoretical for SLM forming process,which is conducive to the popularization and application of SLM technology.