Structure characterization of a laser-processed Al-Mo alloy

The surface structure of a laser-processed Al-Mo alloy has been characteriz ed using scanning electron microscopy (SEM), transmission electron microsco py (TEM) and X-ray diffractory (XRD). The alloy was prepared by first laser alloying a mixture of Al and Mo powders into an Al substrate and then lase r remelting the alloyed surface. Following the fi rst laser alloying proces s, the needle-like equilibrium phases (Al5Mo(h) and Al5Mo(r)) are formed wi th a broad size ranges and distribute inhomogeneously in the alpha-Al solid solution matrix. Th is coarse structure is replaced by a fi ner, uniform d ispersion of dendrites after the subsequent laser remelting. Four basic typ es of solid states precipitates are observed: (1) irregularly shaped partic les constructing the dendrites and having a nearly Al5Mo stoichiometry; (2) needle-like particles which is the Al5Mo (r) phase; (3) Faceted particles having a cubic structure with a stoichiometry close to Al7Mo (4) tiny, equi -axed particles, with a rather narrow particle size distribution and a cubi c structure. (C) 1998 Chapman & Hall.