In-situ Low Rare Earth Alloying for Strength-Toughness Enhancement of AZ31 Mg Alloy

Description

This dataset covers a low-rare-earth Mg-3.34Al-1.59Gd-0.92Zn-0.43Mn alloy with a total rare-earth (RE) content of merely 2.23 wt.% fabricated via pulsed Cold Metal Transfer wire-arc directed energy deposition (pulsed CMT WA-DED) combined with interlayer pre-deposition of Gd/Y powders for in-situ alloying. Characterizations including XRD, SEM, EBSD and TEM verify that RE elements induce the in-situ formation of thermally stable η′-Al₈Mn₄RE heterogeneous nucleants, nano-sized RE-rich β′ phases and dispersed nano η-Al₈Mn₅ particles. Gradual grain refinement is realized via heterogeneous nucleation, constitutional supercooling and particle pinning mechanisms: the average grain size of as-deposited pure AZ31 is 23.6 μm, which reduces to 16.42 μm for the as-deposited RE-containing alloy and further decreases to 10.12 μm after T6 heat treatment. Meanwhile, the basal texture is drastically weakened, interlayer columnar grains are eliminated, the fraction of high-angle grain boundaries (HAGBs) rises, and residual strain is homogenized. Mechanical testing reveals that the as-deposited AZ31 possesses an average microhardness of 49.1 HV, a transverse ultimate tensile strength (UTS) of 218.9 MPa and an elongation of 22.2%. After RE addition, the microhardness rises to 55.3 HV and tensile strength improves, while the elongation drops to 11.8%–14%. Following T6 treatment, the microhardness reaches 60.3 HV; the alloy delivers a transverse UTS of 313.4 MPa and a building-direction UTS of 305.9 MPa, with the average elongation recovering to 19%. The tensile strength anisotropy is only 2.4%, and the comprehensive quality index Q reaches 508 MPa, outperforming most high-RE WA-DED Mg-RE alloys. Fracture morphology transforms from brittle cleavage fracture of monolithic AZ31 to a mixed ductile-brittle fracture dominated by deep dimples after heat treatment. The synergistic contributions of grain-boundary strengthening, RE solid-solution strengthening and Orowan precipitation strengthening from nano secondary phases simultaneously enhance strength, ductility and isotropy of the alloy.

Institutions

• Hebei University of Science and Technology

  Hebei, Shijiazhuang
• Beijing University of Technology

  Beijing, Beijing
• Nanjing University of Science and Technology

  Jiangsu, Nanjing

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