Microstructure and properties of Ti/(TiB+TiC) composites prepared by low-cost TiH2 powders

Abstract

Ti/(TiB+TiC) titanium matrix composites with the excellent mechanical properties were prepared by vacuum pressureless sintering and hot extrusion by using low-cost TiH2 powders instead of pure titanium powders and adding B4C to in-situ produce TiB and TiC reinforcements. The effects of preparation technology and reinforcements on the microstructure and properties of the Ti/(TiB+TiC) composites were analyzed. The results show that the TiH2 powders have the good sintering activity, and the relative density of the sample after dehydrogenation and sintering can reach 97.7%, which is further increased to 99.9% after the hot extrusion as closed to full density. The TiB reinforcements are short fibrous, and the TiC reinforcements are granular, which are uniformly distributed in the equiaxed α-Ti matrix, restraining the growth of equiaxed grains and refining the grains. The hot extrusion process can further refine the grains and make the microstructure more uniform and compact, the as-extruded titanium matrix composites show the high hardness and good matching of strength and ductility. The TiH2+4%B4C (volume fraction) extruded composites have the Vickers hardness of Hv0.3 310, yield strength of 683 MPa, tensile strength of 851 MPa, and elongation of 15.1% after fracture.

Keywords

• tih2 powders
• titanium matrix composites
• hot extrusion
• microstructure
• mechanical properties