Plastic deformation of AZ31B magnesium alloy in the preform and electropulsing treatment process

Abstract

Magnesium alloys exhibit poor formability at room temperature owing to their hexagonal close-packed crystal structure. In this study, a multi-step preform and electropulsing treatment method was applied to the plastic deformation of AZ31B magnesium alloy to improve its cumulative ductility. The mechanical properties, microstructure, and dislocation evolution were investigated using various parameters. The cumulative elongation of all specimens increased significantly, with the maximum approximately twofold higher for the initial specimens. Although the yield strength decreased after the first step, it increased with the following steps. After electropulsing treatment, the specimens were recrystallized and the dislocations were annihilated. The deformed microstructure caused by preform recovered and the recovery degree was associated with the preform and electropulsing treatment parameters. Therefore, the preform and electropulsing treatment method is effective to enhance the ductility of AZ31B magnesium alloy at room temperature, and a set of appropriate pulse current parameters can achieve satisfactory strength and elongation results. Moreover, the effect of the pulse current on the dislocation mobility and climb mainly accounts for the beneficial restoration during the preform and electropulsing treatment process.

A Pulsed Current Application to the Deformation Processing of Materials

“…Due to the increase in deformability, pressure treatment becomes possible without increasing the temperatures of brittle materials that are difficult to deform under normal conditions. A number of studies show that deformation with current can achieve better deformability of titanium alloys [ 61 , 62 ], magnesium alloys [ 16 , 27 , 63 , 64 ], aluminum [ 65 , 66 ], shape-memory alloys based on TiNi [ 67 , 68 ], and some other materials [ 69 ].…”

Electro-plastic effect in Ti-6Al-4V: An experimental and numerical study

“…Many experimental attempts 5,[8][9][10][11][12][13][14][15][16] have been made to understand the material behavior during uniaxial electric-assisted tensile (EAT) or compression tests. Okazaki et al 5 conducted EAT tests (pulsed DC, temperature maintained at ;20°C) on wire specimens of CP titanium and observed that stress-drop increased with an increase in the energy density and attributed the same to the EP effect.…”

“…Zhang et al 14 reported that yield strength decreased (16%) and elongation increased (33%) with electropulsing treatment (current density of 885 A/ mm 2 , 30 min duration) on the pre-strained (14%) AZ31B alloy (uniaxial tension test, temperature ;137°C) compared to that without electric aid and attributed the same to dislocation annihilation. Later the same group, 15 performed both prestrain (at 75% of elongation) and electro-pulsing treatment (current densities of 1000 and 1100 A/mm 2 , maximum duration of 11 min) repeatedly during uniaxial tension of AZ31B and observed that elongation increased with decrease in duration of treatment. Guo et al 16 conducted EAT (pulsed DC) of AZ31B alloy and observed that elongation increased by 41% compared to room temperature tests by suitable selection of pulse parameters (temperature reached is ;268°C and at which microstructural changes are reported).…”