Influence of Particle Size and Shape on the Mechanical Properties of Titanium-Titanium Boride Metal Matrix Composite

Titanium and its alloys offer many attractive characteristics for aerospace application, because of their low density, high specific strength, adequate fatigue strength, and corrosion resistance.   However, titanium is underutilized in the industry due to the high cost of Ti and poor wear resistance.  Powder metallurgy (PM) has been taken into account for producing economical titanium components.  Titanium and its alloys reinforced with ceramic particles, such as TiB, SiC, Al₂O₃, and B₄C, improve their wear resistance and tensile properties.  TiB as reinforcement is attractive because of the absence of an intermediate phase between Ti and TiB.  TiB forms as long, pristine single crystal whiskers in the titanium matrix at relatively lower temperature.  This means that with a small amount of reinforcement, large increase in composite modulus and strength are possible, according to the theories of whisker-induced stiffening and strengthening.

On the other hand, the tensile behavior and wear resistance depends on the reinforcement morphology of the composites.  The difference in the reinforcement morphology is probably due to a different size and shape of raw powders.

In this study, pulverized and gas atomized pure titanium powders were used as the matrix with powder sizes of 45μm and 150μm.  TiB-reinforced titanium composites were prepared by spark plasma sintering.  TiB reinforced titanium with gas-atomized titanium powder of 150μm shows the higher relative density.  The composite with pulverized titanium powder of 45μm had the highest tensile strength and Vickers hardness.  Both tensile strength and Vickers hardness increased with increasing TiB volume fraction.