Structure, properties and fracture of pulsed Nd:YAG laser welded Ti-14.8wt%Al-21.3wt%Nb titanium aluminide

Recent rapid solidification, powder metallurgy and quenching studies on Nb-rich Ti-Al-Nb alloys have determined that rapid cooling suppresses beta decomposition to α/sub 2/ and instead promotes the formation of an ordered BCC β superlattice (CsCl) designated as B2. Based on these observations, the present study was initiated in which a pulsed Nd:YAG laser was utilized to generate a rapidly cooled fusion zone microstructure in Ti-14-21 comprised of a potentially ductile ordered β phase. The authors have determined that the generation of a metastable ordered β-phase can improve weld ductility while providing hardness levels superior to that of the base metal. Although laser processing should alleviate weld cracking, the optimization of weld properties in service will require the determination of an optimum stabilizing heat treatment which provides acceptible room and elevated temperature properties