Influence Of Deformation Rate On Deformation Behavior Of Magnesium Alloy And Research Of Detwinning

At plastic deformation process of hexagonal close-packed structure, deformation twinning is an important mechanism of plastic deformation and has great influence on the mechanical properties of the alloy. In the paper, the influence of rate on deformation behavior of magnesium alloys and influence of annealing treatment on detwinning are researched through Mg-Gd-Y-Zr and AZ31 alloys.Mg-10Gd-3Y-0.3Zr alloy is compressed for different deformation rates at 25℃,150℃ and 175℃. When compression rates are reduced from 1 mm/min to 0.01 mm/min at 175℃, the strength dose not reduce but increase.Because the solute atoms have enough time to segregation to the deformation twin boundary and pin twin boundary, hindering the movement of twin boundary effectively,making the twin slightly thinner and enhancing the strengh of alloys.Strength is increased from 317 MPa to 418 MPa. It does not appear pinning effect of twin at compression of 25 ℃.Pinning effect at compression of 150℃ is weaker than at 175℃. Deformation texture is gradually strengthening in the process of compression, causeing a rotation of the base level and gradually parallelling to the direction of compression. Portevin-Le Chatelie phenomenon is observed in the process of high temperature compression. Rate of atomic diffusion is faster, promoting interaction between solute atoms and dislocations at high temperature.Hot rolled AZ31 alloy compressed along ND can detwin at room temperature for different annealing treatment after pre-compression along TD. Experiment shows that compression presents different mechanical properties and organization at different direction. The yield strength that precompression AZ31 alloy subjected to annealing is obviously improved 20 MPa. Sample without annealing treatment can occur detwinning in the early deformation completely. Sample with annealing treatment can delay the occurrence of detwinning. Precompressed sample with samll amount along the direction of TD first finish detwinning along the direction of ND and strain hardening. Twin-detwin can restore to the initial texture of alloy.Mg-10Gd-3Y-0.3Zr and Mg-2Gd-2Y-0.3Zr alloys are tensile for annealing treatment after first compressed the strain of 5%. Twin area fraction of Mg-2Gd-2Y-0.3Zr is more than that of Mg-10Gd-3Y-0.3Zr alloy, but compressive strength and yield strength are lower than that of Mg-10Gd-3Y-0.3Zr after compression deformation. Mg-10Gd-3Y-0.3Zr alloy can not form detwinning in the subsequent tension after compression, however, Mg-2Gd-2Y-0.3Zr alloy is able to form detwinning. The yield strength of detwinning is increased 20 MPa and number of detwin is more than sample without annealing after annealing treatment. Mg-2Gd-2Y-0.3Zr alloy mostly formed{1012}twin, Mg-10Gd-3Y-0.3Zr alloy exists other types of twinning.