Cai Qi, Li Xinyao, Li Shukui, He Chuan, Liu Xingwei, Feng Xinya
School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China.
China National Key Laboratory of Science and Technology on Materials under Shock and Impact, Beijing Institute of Technology, Beijing 100081, China.
Materials (Basel). 2020 Nov 4;13(21):4957. doi: 10.3390/ma13214957.
The Mg-0.6Al-20.8Gd (wt.%) alloys were homogenized at 620 °C for 20 min under 0 T and 1 T, followed by furnace cooling, quenching, and air cooling, respectively. The effects of the magnetic field on the phase constituent, microstructure, secondary phase precipitation, and mechanical properties of the Mg-Al-Gd alloys were investigated. The Mg-Al-Gd alloys contained α-Mg, MgGd, AlGd, and GdH phases, and the phase constituents were hardly influenced by the applied magnetic field. However, the precipitation of the paramagnetic MgGd upon cooling was accelerated by the magnetic field, and that of the ferromagnetic AlGd phases was inhibited. In addition, the AlGd phase was significantly refined and driven to segregate at the grain boundaries by the magnetic field, and the resultant pinning effect led to the microstructure change from dendritic α-Mg grains to rosette-like ones. When the magnetic field was only applied to the homogenization stage, the content of the MgGd phase remained unchanged in the quenched alloy, whereas the MgGd laths were significantly refined. By contrast, the contents of the AlGd and GdH phases were increased, while the precipitation sites were still within the α-Mg grains. The MgGd laths were incapable of providing precipitation strengthening, while the AlGd and GdH particles brought positive effects on the enhancement of the mechanical properties. In the quenching condition, the hardness, compression strength, and ductility can be improved by the magnetic treatment, whereas these mechanical properties can be suppressed in the furnace cooled condition by the magnetic treatment.
Mg-0.6Al-20.8Gd（重量百分比）合金在620℃下于0T和1T磁场中均匀化处理20分钟，随后分别进行炉冷、淬火和空冷。研究了磁场对Mg-Al-Gd合金的相组成、微观结构、第二相析出以及力学性能的影响。Mg-Al-Gd合金包含α-Mg、MgGd、AlGd和GdH相，相组成几乎不受外加磁场的影响。然而，冷却时顺磁性MgGd的析出被磁场加速，而铁磁性AlGd相的析出受到抑制。此外，AlGd相被磁场显著细化并驱使其在晶界处偏聚，由此产生的钉扎效应导致微观结构从树枝状α-Mg晶粒转变为玫瑰花状晶粒。当仅在均匀化阶段施加磁场时，淬火合金中MgGd相的含量保持不变，而MgGd板条显著细化。相比之下，AlGd和GdH相的含量增加，而析出位置仍在α-Mg晶粒内。MgGd板条无法提供析出强化，而AlGd和GdH颗粒对力学性能的增强产生积极影响。在淬火条件下，磁处理可提高硬度、抗压强度和延展性，而在炉冷条件下，磁处理会抑制这些力学性能。
