Powder metallurgy

Abstract

Powder metallurgy (PM) technology has undergone advances of a breakthrough nature in the past few years. For example, rapid solidification offers new refinements in microstructure, extension of alloying, the ability to fabricate previously unprocessable compositions, and production of previously unobtainable crystalline and amorphous structures. Mechanical alloying offers dispersion-strengthened materials having elevated-temperature capability beyond conventional cast ingot and wrought material, and greater excursions from equilibrium than rapid solidification. Pushing the horizons even further are nanostructures, where the crystal grains are of a size (tens of nm) where more than half the atoms present are not located on a crystal lattice. In addition, composites offer performance capabilities beyond the accepted norm for monolithic materials. In this area, synthesis can include evolving fabrication techniques such as spray deposition, providing not only novel microstructures, but also the ability to produce near-net shapes directly. Powder metallurgy is also amenable to rate-dependant processes such as thermochemical processing. In this technique, hydrogen is used as a temporary alloying element to enhance the processability and mechanical properties of hydride-forming elements such as titanium. A table shows projected growth for rapid solidification materials in the US to 1993.