A systematic study of channel-angle effects on microstructure, strength-ductility, and corrosion behavior of high-purity magnesium in forward-parallel extrusion

초록

This work systematically investigated the processing of high-purity magnesium by forward extrusion (FE) and forward-parallel extrusion (FPE) with three different channel angles of 90 degrees, 105 degrees and 120 degrees. Tensile testing, electrochemical measurements, hydrogen evolution, weight loss tests and microstructural characterization were employed to clarify how the additional FPE shear path tailored the microstructure, mechanical properties and corrosion behavior relative to conventional FE. Compared with Phi 10FE, FPE produced finer and more homogeneous grain structures, increased the fraction of high-angle grain boundaries and further weakened the basal texture. The yield strength increased from 33 MPa after Phi 10FE to approximately 71 MPa after all FPE routes. The ultimate tensile strength was also markedly enhanced, increasing from 119 MPa for Phi 10FE to 191 MPa, 182 MPa and 197 MPa for 90 degrees FPE, 105 degrees FPE and 120 degrees FPE, respectively. Meanwhile, the elongation improved from 7.5% for Phi 10FE to 10.1% and 9.8% for the 90 degrees FPE and 105 degrees FPE samples, respectively, while the 120 degrees FPE sample retained a high elongation of 9.0% together with the highest tensile strength. Long-term immersion tests further showed that FPE reduced hydrogen evolution compared with Phi 10FE, with the 90 degrees FPE sample showing the lowest hydrogen release and corrosion rate. The corrosion-rate order was 90 degrees FPE <105 degrees FPE <120 degrees FPE < Phi 10FE < cast. These results demonstrate that FPE provides additional microstructural and property advantages over conventional FE, and that channel-angle selection enables high-purity Mg to be tuned toward either higher strength or improved ductility/corrosion resistance.

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