Superplastic Deformation Behavior of Rolled Mg-8Al-2Sn and Mg-8Al-1Sn-1Zn Alloys at High Temperatures

Abstract

The high-temperature superplastic deformation behavior of rolled Mg-8Al-2Sn (AT82) and Mg-8Al-1Sn-1Zn (ATZ811) alloys were investigated in this study. During tensile deformation at 573 K, no obvious grain growth occurred in both alloys, because of the high-volume fraction of second phases located at grain boundaries. Meanwhile, texture weakening was observed, suggesting that grain boundary sliding (GBS) is the dominant superplastic deformation mechanism, which agreed well with the strain rate sensitivity (m) and the activation energy (Q) calculations. The microstructural evolution during tensile deformation manifested that there were more and larger cavities in AT82 than ATZ811 during high-temperature tensile deformation. Therefore, superior superplasticity was found in the ATZ811 alloy that presented a tensile elongation of ~510% under a strain rate of 10−3 s−1 at 573 K, in contrast to the relatively inferior elongation of ~380% for the AT82 alloy. Meanwhile, good tensile properties at ambient temperature were also obtained in ATZ811 alloy, showing the ultimate tensile strength (UTS) of ~355 MPa, yield strength (YS) of ~250 MPa and elongation of ~18%. Excellent mechanical performance at both ambient and elevated temperatures can be realized by using economical elements and conventional rolling process, which is desirable for the industrial application of Mg alloy sheets.

Enhanced Mechanical Properties and Isotropy of Mg-2Al-0.8Sn Alloy through Ca Addition

“…The YSs of all samples result from the synergetic role of fine grains, tiny precipitates, solute atoms, and residual dislocation density [22]. The contribution of fine grains (𝜎 ) can be determined by the Hall-Petch relationship [23]:…”

“…Therefore, the strengthening contribution from solute atoms can be estimated by the following formula [31]: The YSs of all samples result from the synergetic role of fine grains, tiny precipitates, solute atoms, and residual dislocation density [22]. The contribution of fine grains (σ grain ) can be determined by the Hall-Petch relationship [23]:…”

High Strain Rate Superplasticity in Al-Zn-Mg-Based Alloy: Microstructural Design, Deformation Behavior, and Modeling

“…Superplastic deformation was accompanied by cavitation, which is typical of aluminum-based alloys [18,21,72]. As the grain boundary sliding (GBS) is a dominant superplastic deformation mechanism [71][72][73], the coarse secondary particles on the grain boundaries are expected to act as nucleation sites for strain-induced cavities [72]. In the studied alloy, the cavities formed near the eutectic particles and far from them (Figure 3c), but the volume fraction of the residual cavities reached only 1.2% after deformation to failure.…”