A STUDY OF WELD HEAT-AFFECTED ZONES IN THE TITANIUM - 6A1-6V-2SN ALLOY
WATERVLIET ARSENAL NY
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A new high-strength alpha-beta type titanium alloy was recently developed which is heat treatable to useful yield strengths above 180,000 psi, with 7 percent elongation, 16 percent reduction in area, and 7 ft.-ibs. Charpy V-notch impact energy at -40 F. Preliminary manual welding experience with this alloy disclosed a strong tendency for cracking in the heat-affected zone. This study was performed to determine resultant toughness in the heat affected zones for various welding conditions. Preheat was the most influential factor in retaining toughness in solution treated and aged base metal welding without it caused severe losses in impact strength and notched tensile strength which could not be recovered by aging treatments afterwards or resolution treating and aging. Mechanisms causing changes in properties involving beta becomes alpha and beta becomes alpha on cooling, and alpha becomes alpha beta and beta becomes alpha upon reheating were studies by X-ray diffraction volumetric analysis and photomicrographic techniques. No evidence of omega phase forming or transforming was found in the aging procedures studied.
- Fabrication Metallurgy
- Couplers, Fasteners and Joints