Biform resolidification and amorphous phases in a laser and electron beam processed tantalum-iridium alloy

A 50 at. % Ta-Ir alloy has been surface melted by a CW CO/sub 2/ laser and, in a separate study, by a CW electron beam. Metallographic and transmission electron microscopic analysis has revealed both a microcrystalline region and amorphous regions in the resolidified layers. Evidence has been found by TEM that amorphous regions of two distinct compositions exist in the laser-irradiated case. A two-dimensional finite element heat flow analysis has been used to estimate cooling rate and resolidification velocities.