ALLOYING OF AL3TI TO FORM CUBIC PHASES

The recent discovery of cubic L1(2) trialuminides formed by alloying normally tetragonal Al3Ti with Cr, Mn and Co, when combined with previous work with Fe, Ni, Cu and Zn as cubic stabilizing elements, makes it possible to examine changes in properties and structure as a function of the stabilizing element. In particular, the improvement in mechanical properties with the decreasing atomic number of the stabilizing element, Zn to Cr, can be related to decreased bond strengths as shown by changes in the lattice constant and elastic moduli. As expected, there are corresponding changes in the nature of the dislocations carrying the plastic deformation. Recent attempts to understand the fracture behavior of the cubic forms are discussed. Determinations of the cyclic oxidation resistance and the coefficient of thermal expansion for the alloys with best mechanical properties, Al67Cr8Ti25 and Al67Mn8Ti25, are also presented.