Hot compression behavior and 3D processing maps of Mg-Gd-Y-Zn alloy formed by cold metal transfer wire arc additive manufacturing

Based on hot compression experiments, the hot deformation behavior and workability of the Mg-Gd-Y-Zn alloy fabricated by cold metal transfer wire arc additive manufacturing (WAAM-CMT) were studied. The compression experiments were performed at temperatures ranging from 350 to 500 °C, with strain rates between 0.001 and 1 s −1 . The results indicate that the peak stress of the alloy decreases significantly with lower strain rates and higher deformation temperatures. Combined with the analysis of the Arrhenius type equation (Eq.), the average value of the recrystallization activation energy (Q) was 308.4 kJ/mol. Utilizing the Zener-Hollomon parameter, we derived the constitutive Eq. for the deposited Mg-Gd-Y-Zn alloy during hot deformation: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mspace width="0.25em"/> <mml:mrow> <mml:mover> <mml:mi>ε</mml:mi> <mml:mo>˙</mml:mo> </mml:mover> </mml:mrow> <mml:mo>=</mml:mo> <mml:mn>2.499</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>21</mml:mn> </mml:msup> <mml:mo stretchy="false">[</mml:mo> <mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">sinh</mml:mi> </mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mrow> <mml:mn>0.0095</mml:mn> <mml:mi>σ</mml:mi> </mml:mrow> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:msup> <mml:mo stretchy="false">]</mml:mo> <mml:mrow> <mml:mn>7.02</mml:mn> </mml:mrow> </mml:msup> <mml:mo>⋅</mml:mo> <mml:mrow> <mml:mi mathvariant="normal">exp</mml:mi> </mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3.084</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>5</mml:mn> </mml:msup> <mml:mo>/</mml:mo> <mml:mi>R</mml:mi> <mml:mi>T</mml:mi> </mml:mrow> <mml:mo stretchy="false">)</mml:mo> </mml:math> . Using the dynamic material model, we established a three-dimensional (3D) processing maps for the deposited Mg-Gd-Y-Zn alloy. The main instability domain were temperatures from 350 to 385 °C with strain rates of 0.1 to 1.0 s −1 , and temperatures from 435 to 500 °C with strain rates of 0.4 to 1.0 s −1 . Considering the power dissipation map, the stable and power-efficient forming domains is in the temperature range from 435 to 500 °C and strain rate range from 0.001 to 0.04 s −1 . Due to dynamic recrystallisation (DRX), the grain of the deposited Mg-Gd-Y-Zn alloy is significantly refined after hot deformation. These findings provide valuable guidance for selecting integrated process equipment and optimizing deformation parameters for additive and on-line micro-forged magnesium rare earth alloys.