Microstructures and mechanical properties of Gas Tungsten Arc Welded joints of new Al–Mg–Sc and Al–Mg–Er alloy plates

The effect of microalloy element Sc and Er on Gas Tungsten Arc Welded (GTAW) joints of Al–Mg alloy was studied by comparative method. The microstructures and mechanical properties of Al–Mg–Sc and Al–Mg–Er alloy welded joint were examined by microhardness measurement, tensile test, optical microscopy and transmission electron microscope. The strength of Al–Mg–Sc welded joint is higher than that of Al–Mg–Er welded joint. The differences of the two welded joints can be attributed to the different thermal stability and the effect of Al3(Sc1−x,Zrx) particles and Al3(Er1−x,Zrx) particles. Al3(Sc1−x,Zrx) particles, which have higher thermal stability, are still coherent with Al matrix in the HAZ, can strongly pin dislocations and subgrain boundaries of the HAZ. There are strain strengthening and precipitation strengthening in the HAZ of Al–Mg–Sc welded joints. Notable coarsening of Al3(Er1−x,Zrx) particles and recrystallization in the HAZ of Al–Mg–Er welded joint lead to the reduction and disappearance of strain strengthening and precipitation strengthening.