The Effect of Zirconium and Yttrium Oxide on the Microstructure and Mechanical Properties of Ti-Si-Zr Based Composites

Abstract

Ti-4Si-xZr-yY2O3/5TiO2 matrix composites, containing various weight percentages (0 and 1.3) of zirconium and (0 and 0.3) yttrium oxide, were synthesized via ball milling and powder metallurgical route. Mechanical alloying of the powders was confirmed after ball milling using x-ray diffraction (XRD) and scanning electron microscope (SEM). The ball-milled powders were cold compacted at a pressure of 550 MPa. Sintering was done first at 600 °C for 2h, followed by 800 °C for 2h, then 1000 °C for 2h and finally at 1250 °C for 3h, all in a controlled vacuum environment. The effect of the addition in weight percentages of Zr and Y2O3 on the microstructure, porosity, hardness, elastic modulus, and fracture toughness of the sintered composites, were studied. The results show improvements in the microhardness by 2.2 times, elastic modulus by 34.3%, porosity by 50 %, and fracture toughness by 57%, when Zr and Y2O3 content was 1.3 wt% and 0.3 wt%, respectively. The improvements in the microstructure and mechanical properties can be attributed to the formation of more stable; Ti5Si3 and Ti5Si4 phases and the solid solutions of Ti2Zr, Zr3Si2, and Ti2Zr3Si3 compounds.