Microstructures and mechanical properties of zirconium-containing 7×××aluminum alloy prepared by selective laser melting

The preparation of 7×××series aluminum alloy by selective laser melting technology (SLM) is hindered by hot tearing. Novel ZrH2 modified 7075 composite powders were prepared by the low-energy ball milling technology. Zirconium-containing 7×××series aluminum alloy was then prepared by the SLM process. The microstructure and mechanical properties of the samples with different ZrH2contents (0.5%, 1.0%, 1.5%, mass fraction, the same below) were systematically investigated. The results show that the addition of ZrH2 can significantly reduce hot tearing and change the microstructure. When 1.5% ZrH2 is added, the hot tearing is completely eliminated and the grain microstructure is entirely composed of fine equiaxed grains. The transition of columnar grains to equiaxed grains is attributed to the in-situ formation of L12-Al3Zr which provides numerous nucleation positions for solidification. After T6 heat treatment, the tensile strength, yield strength and elongation of SLMed sample are (550±10), (490±5) MPa and (12±1)%, respectively. Fractography analysis shows a large number of dimples on the fracture surface after tensile testing, indicating ductile fracture mode.