Evaluation of Dynamic Deformation Behavior of LPSO Type Magnesium Alloy by AE Method and High Speed Camera

Introduction

machinery to improve fuel consumption has been desired from the viewpoint of global warming and other environmental problems. One proposed solution is use of magnesium alloys, which are lighter in weight than other structural materials. The density of magnesium is 1.73 g/m3 , which is the lowest among practical metal materials, being about 2/3 that of aluminum and 1/4 that of steel. Magnesium also has the advantages of superior specific strength, specific proof stress, vibration damping capacity, heat dissipation, dimensional stability, electromagnetic shielding capacity, machinability, and recyclability. However, because general magnesium alloys have a hexagonal closest-packed structure (HCP crystal structure), as shown in Fig. 1, large-scale plastic deformation at room temperature is not as easy as with other crystal structures. Moreover, the mechanical properties of magnesium alloys are not significantly superior to those of aluminum alloys. Due to these issues, little progress has been made in practical application. The Long-Period Stacking Ordered (LPSO) type magnesium alloy, which was developed by Kawamura et al. 1) in 2001, simultaneously achieves high strength, high heat resistance, and incombustibility, and has been an object of active research. Kawamura et al. realized the LPSO structure with Mg97Zn1Y2 by the rapid solidification powder metallurgy method. The LPSO structure, as its name suggests, is a structure with a long-span atomic arrangement in comparison with conventional magnesium alloys. It has been reported that a deformation mechanism called kink deformation occurs in microregions in this LPSO structure, and the formation of kink deformation bands is thought to contribute to high strength. Hagihara et al. 2) performed compressions tests of unidirectionally solidified materials having a LPSO single phase structure and investigated the orientation change caused by the deformation bands. The orientation change caused by deformation bands does not take a fixed value like that in the case of twinning deformation, but rather, displays a wide distribution. Based on this, some researchers have maintained that deformation bands are caused by kink deformation and not twinning deformation. On the other hand, Kishida et al. 3) proposed that the distinctive deformation bands formed by Mg-Al-Gd system alloys that contain the LPSO phase are not formed by kink deformation, but by twinning deformation followed by crystal rotation. Since the twins that occur here are a twin system called {112ത1} tensile twins and have rarely been reported in magnesium and its alloys, it is possible that the LPSO structure plays a critical role in the formation of this twin system. Thus, there are still many unknown points in connection with the kink deformation of the LPSO phase, and it is necessary to elucidate the detailed behavior of this kink deformation for further alloy development of LPSO type magnesium alloys.

October 29, 2025 GMT