Tokunaga Toko, Hagihara Koji, Yamasaki Michiaki, Mayama Tsuyoshi, Yamamoto Kazuki, Narimoto Hiroki, Kida Taiki, Kawamura Yoshihito, Nakano Takayoshi
Department of Physical Science and Engineering, Nagoya Institute of Technology, Nagoya, Aichi, Japan.
Division of Materials and Manufacturing Science, Graduate School of Engineering, Suita, Osaka, Japan.
Sci Technol Adv Mater. 2022 Nov 3;23(1):752-766. doi: 10.1080/14686996.2022.2137696. eCollection 2022.
The variation in the mechanical properties with the volume fraction of the long-period stacking ordered (LPSO) phase in directionally solidified (DS) Mg/LPSO two-phase alloys was examined. Unexpectedly, the yield stress of the DS alloys increases non-monotonically with an increase in the volume fraction of the LPSO phase. The LPSO phase is considered an effective strengthening phase in Mg alloys, when the stress is applied parallel to the growth direction. Nevertheless, the highest strength was obtained in alloys with 61-86 vol.% of the LPSO phase, which was considerably higher than that in the LPSO single-phase alloy. It was clarified that this complicated variation in the yield stress was generated from the change in the formation stress of kink bands, which varied with the thickness of the LPSO-phase grains. Furthermore, the coexistence of Mg in the LPSO phase alloy induced the homogeneous formation of kink bands in the alloys, leading to the enhancement of the 'kink-band strengthening'. The results demonstrated that microstructural control is significantly important in Mg/LPSO two-phase alloys, in which both phases exhibit strong plastic anisotropy, to realize the maximum mechanical properties.
研究了定向凝固（DS）Mg/LPSO两相合金中力学性能随长周期堆垛有序（LPSO）相体积分数的变化。出乎意料的是，DS合金的屈服应力随着LPSO相体积分数的增加而非单调增加。当应力平行于生长方向施加时，LPSO相被认为是Mg合金中的有效强化相。然而，在LPSO相体积分数为61-86 vol.%的合金中获得了最高强度，这大大高于LPSO单相合金中的强度。结果表明，屈服应力的这种复杂变化是由扭折带形成应力的变化引起的，该应力随LPSO相晶粒的厚度而变化。此外，LPSO相合金中Mg的共存导致合金中扭折带的均匀形成，从而增强了“扭折带强化”。结果表明，在Mg/LPSO两相合金中，微观结构控制对于实现最大力学性能具有重要意义，其中两相均表现出强烈的塑性各向异性。
