Mechanical assessment of autogenous gas tungsten arc weldments of a super alpha-2 alloy
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Butt welding of a 2-mm-thick super alpha-2 alloy (Ti-23Al-9Nb-2Mo-0.9Si) was carried out employing autogenous gas tungsten arc technique. Process parameters were adjusted to achieve full-penetration weld. Only β-Ti-based phase was detected in the fusion zone; however, minor quantities of a Ti3Al-based structure were found at heat input higher than 518 J mm−1. No cracking was observed within the fusion zone and its associated heat-affected zones. Subgrain boundaries and acicular transformation products were observed within the HAZ grains. The acicular transformation products are believed to be responsible for the higher microhardness value of the HAZ compared to those of the fusion zone and base material. It was found that the fusion zone and HAZ had lower strength and ductility than the base material. Fracture occurred within the HAZ, which is attributed to its higher microhardness value and acicular transformed microstructure. The maximum weld tensile strength achieved was about 90% of that of the base material.
KeywordsWelding Heat Input Fusion Zone Cleavage Fracture Titanium Aluminide
Thanks are to Dr. S. Kerry of DRA Farnborough, England, for providing the base material and to University of Tehran for financial support for the present research.
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