Study on the aluminium-magnesium-silicon alloy (6th Report)

Abstract

This is to report on the study of the cracking in the heat-affected zone and the mechanical properties and electrical conductivity of the welded products of Al-Mg-Si alloy with different Mg/Si weight ratio.The findings are as follows:(1) Weldability of Al-Mg-Si alloy is affected by the content of magnesium and silicon. Al-Mg-Si alloys containg Mg2Si of 0.5% to 1.0%, in the region of excess-Si, show the maximum tendency of weld heat-affected zone cracking.(2) Among the various kinds of filler metals, for example the same alloy, Al-0.8% Mg alloy and 4043 alloy, the welded products by the filler metal of 4043 alloy show the minimum tendency of weld heat-affected zone cracking.(3) As to the joint efficiency of welded products, annealed material has the joint efficiency of 100% in tensile strength, 120 to 150% in proof stress and 100% in electrical conductivity after welding, and such efficiency is regardless of the kinds of filler metals used in this experiment. Therefore, it is practically available without any trouble to use annealed materials for welding. T6 heat treated material has the joint efficiency of 50% to 60% in strength after welding and it is affected by the Mg/Si ratio, the filler metals and the speed of welding. Its efficiency can also be increased a little by the precipitation heat treatment after welding. However, it is more desirable to narrow the weld heat-affected zone by using the high speed welding method.