Solidification crack and morphology for laser weave welding of Al 5J32 alloy

Linear and weaving laser welding were performed on a self-restraint tapered specimen of an Al 5J32 alloy. Linear welding produced columnar grains along the fusion line and equiaxed grains along the centreline. Solidification crack developed along the centreline having equiaxed grains. For laser weave weld, the solidification crack disappeared at a weaving frequency of 5 Hz. However, as the weaving frequency increased further, the length of the columnar grains inside the weaving trajectory curve became smaller than that outside the curve, and the equiaxed grains did not necessarily grow along the centreline of the weld. Therefore, the wide equiaxed grains deviated from the transverse weaving profile and a near linear solidification crack developed. The simulated morphology using solidification rate and temperature gradient correlated well with the solidification morphology obtained from the experiments. The limiting boundary condition for differentiating between the columnar and the equiaxed microstructures in the alloy was G = 3·5 R.