Synthesis of high-strain-rate superplastic magnesium alloy sheets using a high-ratio differential speed rolling technique

Influence of texture on superplastic behavior of friction stir processed ZK60 magnesium alloy

“…Therefore, studies on the superplastic deformation of magnesium alloys have mainly been focused on optimizing the microstructure via various plastic deformation methods, such as equal channel angular pressing (ECAP) [2][3][4], hot rolling [5], extrusion [6], friction stir processing (FSP) [7,8], and differential speed rolling (DSR) [9]. However, as commonly observed in hexagonal closepacked metals, texture was often developed and was proved to influence the mechanical properties of magnesium alloys at both room and high temperatures [10].…”

Two different types of deformation behaviors in ultrafine grained Mg alloys at high temperatures and development of the generalized constitutive equation for describing their deformation behavior

“…There are two commercial composition-based magnesium alloys that exhibit good superplasticity: Mg-Al-Zn (AZ) and Mg-Zn-Zr (ZK) alloys, which contain second phase particles that are necessary to develop and stabilize the fine-grained microstructures. Many researchers have studied the enhancement of superplasticity of these magnesium alloys by decreasing their grain sizes [1][2][3][4][5][6][7][8][9][10][11][12]. Severe plastic deformation (SPD), such as equal-channel angular pressing (ECAP) and accumulative roll bonding, is an effective method to produce bulk material with ultrafine-grained (UFG) grains in many metals, including Mg alloys.…”

“…Severe plastic deformation (SPD), such as equal-channel angular pressing (ECAP) and accumulative roll bonding, is an effective method to produce bulk material with ultrafine-grained (UFG) grains in many metals, including Mg alloys. Grain size reduction by SPD decreases the lower limit of temperature for superplasticity by increasing the contribution of grain boundary sliding to the creep deformation rate at low temperatures (r 0.5T m , where T m is the melting temperature of the material of interest), allowing for achievement of lowtemperature superplasticity [1,2,4,5,8,9]. For example, an ECAPprocessed AZ61 (Mg-6Al-1Zn) alloy exhibited a tensile elongation of 1190% at a strain rate of 3 Â 10 À 5 s À 1 at 448 K [2], and an ECAPprocessed ZK60 (Mg-6Zn-0.5Zr) alloy exhibited a very large tensile elongation of 2040% at 3 Â 10 À 4 s À 1 at 493 K [5].…”

“…Thus, control over the size and distribution of second phase particles is crucial in achieving high-strain-rate superplasticity (HSRS). Kim et al [8] discovered a route for developing thermally stable UFG microstructures of a ZK60 alloy using the high-ratio differential speed rolling (HRDSR) technique under controlled processing conditions. The HRDSR-processed ZK60 alloy exhibited HSRS with a large tensile elongation of 926% at 1 Â 10 À 2 s À 1 at 553 K [8].…”

“…Kim et al [8] discovered a route for developing thermally stable UFG microstructures of a ZK60 alloy using the high-ratio differential speed rolling (HRDSR) technique under controlled processing conditions. The HRDSR-processed ZK60 alloy exhibited HSRS with a large tensile elongation of 926% at 1 Â 10 À 2 s À 1 at 553 K [8]. The UFG AZ91 (Mg-9Al-1Zn) alloy with good thermal stability, which was prepared by submerged friction stir processing, also exhibited HSRS with a tensile elongation of 990% at 2 Â 10 À 2 s À 1 at 623 K [11].…”