1997 Volume 83 Issue 12 Pages 821-826
Conventional titanium alloys such as Ti-6Al-4V show lower stiffness, poorer abration-related properties and poorer high temperature properties than nickel-based alloys. In order to overcome these drawbacks, an attempt was made to produce titanium-based particulate composites using the blended elemental powder metallurgy method. Firstly, the effect of titanium powder size on the sintered density and how to disperse the reinforcing ceramic particulates uniformly in the matrix were investigated in detail to optimize processing conditions. It was shown that the size of titanium powder needs to be smaller than 45μm (-325mesh) to raise the sintered density to a critical value of 95%. The uniform distribution of the particulates was accomplished by a forced mixing technique with a mechanofusion apparatus. Secondly, Ti-6Al-2Sn-4Zr-2Mo/TiB composites were produced using the above processing conditions. The composites showed superior tensile properties, Young's modulus and high cycle fatigue strength compared with those for the matrix alloy. For example, high cycle fatigue strength at 107 cycles was increased to 490MPa from 333MPa for the matrix alloy by the dispersion of 10% TiB. The tensile and Young's modulus data were compared with those predicted by the existing models, and three main factors such as the increase in tensile strength, increase in Young's modulus and matrix microstructure refinement were found to contribute to the increase in high cycle fatigue strength.