first of all, i cant believe u're asking this here. u're a very lasy mechanical eng. student Samuel Olad. so u want people on the forum to do the home assignment for u? your teacher Asif won't appreciate it. secondly, i can help u with some hints on the assignment. effects are :changes in the microstructure and in mechanical properties microstructure is about: what had happened in: fusion zone, partially melted zone and heat affected zone during welding and how these changes have affected the weld in terms of grain growth, phases that are formed. for exmple, in the fusion zone of Alum. alloys in laser welding this is what happens: The grain structure in laser-welded of Al-Mg-Si and Al-Mg alloys primarily consist of fine columnar dendrites, originating from the fusion line and some equiaxed grains in the weld center. Higher travel speeds lead to a more elongated weld pool which leads to finer dendrite structures and grain sizes, resulting from low heat input. Lower welding speeds cause columnar grains to curve away from the normal and they align themselves with the welding direction eventually Depending on the Mg contents in Al alloys, oxides such as Al2O3, Al2MgO4, MgO, or their combination may occur. mechanical properties: remember any changes in the material's microstructure will alter its mechanical properties. discuss the mech. properties ( strength, hardenss, ductility and fatigue) basing on the effects of what happened in weld's microstructue. for example: in the fusion zone there is formation of new grains due to high temperature above recrystallisation's. this will decrease the weld' strength if the new grains are bigger than that of the base metal. for ductility of alum. alloy in laser welding, it goes as this: Because lower welding speeds cause columnar grains to curve away from the normal and they align themselves with the welding direction eventually. There is a decrease in ductility with increase in welding speed. u gotta hurry up, the due date is on dec. 12/ good luck