Microstructure and mechanical properties of laser deposition repair casting ZL114A aluminium alloy

Abstract:

ZL114A casting aluminum alloy with pre-groove damage was repaired by laser deposition repair (LDR). Microstructure and distribution law of laser deposition repaired zone before and after heat treatment were analyzed, and then microhardness and room temperature tensile properties of the sample were tested. The results showed that the repaired parts and the substrate formed a good metallurgical combination, at the bottom of the deposition layer were α-Al columnar dendrites which approximately paralleled to the normal directions of the fusion line with epitaxial growth feature. The primary dendrite arm spacing is about 15.7 μm,and the distance between secondary dendrites is about 5.27 μm. Eutectic structure presented as bifurcated rod or block in shape, and continuously distributed in the gaps among dendrite crystals, and α-Al columnar dendrites transformed into equiaxed crystal at the top of the last deposition layer. After the heat treatment, secondary dendrite arm of columnar dendrite is expansive because of atomic diffusion, and eutectic Si granulation were clear to be observed, the particle size is about 4.93 μm, and part of them distributed uniformly on both sides of primary dendritic arm. The hardness of repair area increased by an average of 55.5% than substrates after heat treatment, and the room temperature tensile properties were better than casting parts.