TABLE OF CONTENTS The MA titanium base alloys are still in the research state, but some interesting advances have been made in the following:
Ti-Mg immiscible;
dispersion strengthened Ti xAl and Ti 5Si 3.
Though Ti-Mg forms an immiscible system and solubility obtained of Mg in titanium by conventional methods is negligible, it is an attractive alloying element to titanium due to its low density. Using MA, solid solution of Mg up to 3.1% in titanium has been achieved [28]. Magnesium also appears to be a very strong ? stabiliser, which depresses the ? transus in binary Ti-Mg as well as in ternary Ti-Mg-Gd systems.
Titanium aluminides based on ?-TiAl (L1 structure) are potentially very attractive low-density materials for use at elevated temperatures in aerospace applications. However, these alloys, like most intermetallics suffer from low ductility and fracture toughness at ambient temperatures due to the presence of a superlattice, and low corrosion resistance even at the moderately high temperature. However, the inherent brittleness of these alloys limits their fabricality. Alloying additions such as Mn for ductility and Cr and Nb for oxidation resistance improve these properties appreciably. The nanocrystalline equiaxed ?-grains and the fine lamella ?/ ? 2 microstructure also results in the same effects. The MG process has been applied to two such alloys [29,30], Ti-25% Al-10% Nb-3% V-2% Mo(at%) and Ti-48% Al-2% Mn-2% Nb(at%). The microstructure of the consolidated gas atomised powder shows a mainly uniform two-phase structure consisting...
