The transformation temperature is strongly influenced: by the interstitial elements oxygen, nitrogen, and carbon (alpha stabilizers), which raise the transformation temperature; by hydrogen (beta stabilizer), which lowers the transformation temperature; and by metallic impurity or alloying elements, which may either, raise or, lower the transformation temperature [ASM6]. Depending on their microstructure, titanium alloys have been conservatively classified into three categories: alpha alloys (consisting of various grades of commercially pure titanium alloys, also contain only trace or limited amounts of beta phase); alpha + beta alloys (presenting alpha stage and a small volume fraction of beta phase in symmetry, although martensite transformation can also occur upon fast cooling); and beta alloys (which do not transform martensitically upon fast cooling from the beta phase field) (Lütjering,Williams, 2007: …show more content…
Good results are generally obtained when laser welding is applied to titanium alloys. The high-energy-density welding processes to produce full-penetration, single-pass welds during laser welding, minimizes the difficulties associated with conventional welding methods, regarding to distortion and residual stress (Costaeal., 2007), where the physical properties of titanium make laser a good choice for welding its alloys, its low thermal conductivity prevents heat dissipation, and its low coefficient of thermal expansion, avoids the appearance of stresses during welding. Also the good absorption rate of titanium, for the laser beam, and its high melting point (Bertrand et al., 2007), indicate that, high energy must be used to weld these alloys, thus laser welding is an adequate technology to join these