tailieunhanh - Partially melted zone

Formation of partially melted zone Consider welding of Cu 2219 alloy • Metal at position a is completely melted. • Metal at position b is heated upto between the eutectic temperature TE and the liquidus temperature TL. The metal becomes a solid + liquid mixture partially melted. • Metal at position c is not melted at all. WM PMZ BM Formation of PMZ in 2219 | Part II Partially meted zone Grain boundary segregation is one of the serious problems observed in partially melted zone. This unfortunately lowers the mechanical properties of the welds. The liquated and re-solidified material along the grain boundary is shown in fig a dark-etched area is eutectic GB and a lighter etched area is a Al-rich band along GB . - making grain boundary weaker. a PMZ microstructure of GMAWin 6061 aluminium made with 4145 aluminium filler wire b enlarged. Suranaree University of Technology Formation of partially melted zone Consider welding of Cu 2219 alloy Metal at position a is completely melted. Metal at position b is heated upto between the eutectic temperature TE and the liquidus temperature TL. The metal becomes a solid liquid mixture partially melted. Metal at position c is not melted at all. Formation of PMZ in 2219 aluminium weld a Al-rich side of Al-Cu phase diagram b thermal cycles c transverse cross section. Suranaree University of Technology Tapany Udomphol Sep-Dec 2007 Microstructure evolution in PMZ of Cu 2219 allo g w 1 At T Te microstructure of the base metal consists of a and 0 Al2Cu within grains and along GB see fig a . At T Te eutectic reaction occurs a 0 Le liquid of eutectic composition CE . Cooling at this point gives microstructure of eutectic particles and some GB eutectic fig b and c . At T Te liquation inside PMZ intensifies more a dissolve into liquid phase changing composition to hypoeutectic liquid. Cooling at this point gives Cu-depleted a and Cu rich eutectic. Suranaree University of Technology Microstructure evolution in PMZ of 2219 Al alloy. f A-j eutectic eutectic 20 um during welding after welding eutectic liquid 0 hypoeutectic r V -liquid . GB eutectic T Eutectic Udomphol Sep-Dec 2007 at T Te PMZ fusion 5 o zone more a melted Into liquid at T TE W um I base metal 2219 Al o no liquation at T Te .