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In this study, interconnected porous Mg-2Zn-xY alloys with different phase compositions were prepared by various Y additions (x = 0.4, 3, and 6 wt. %) to adjust the compressive properties and energy absorption characteristics. Several characterization methods were then applied to identify the microstructure of the porous Mg-Zn-Y and describe the details of the second phase. Compressive tests were performed at room temperature (RT), 200°C, and 300°C to study the impact of the Y addition and testing temperature on the compressive properties of the porous Mg-Zn-Y. The experimental results showed that a high Y content promotes a microstructure refinement and increases the volume fraction of the second phase. When the Y content increases, different Mg-Zn-Y ternary phases appear: I-phase (Mg3Zn6Y), W-phase (Mg3Zn3Y2), and LPSO phase (Mg12ZnY). When the Y content ranges between 0.4% and 6%, the compressive strength increases from 6.30 MPa to 9.23 MPa, and the energy absorption capacity increases from 7.33 MJ/m3 to 10.97 MJ/m3 at RT, which is mainly attributed to the phase composition and volume fraction of the second phase. However, the average energy absorption efficiency is independent of the Y content. In addition, the compressive deformation behaviors of the porous Mg-Zn-Y are altered by the testing temperature. The compressive strength and energy absorption capacity of the porous Mg-Zn-Y decrease due to the softening effect of the high temperature on the struts. The deformation behaviors at different temperatures are finally observed to reflect the failure mechanisms of the struts.

Plasma electrolytic oxidation (PEO) technology was used to deposit a ceramic coating on the strut of open-cell Mg foams. In this experiment, the microstructure, the phase composition, and the elemental distribution of the PEO-coated Mg foams were investigated. Effect of the PEO treatment on the compressive properties and the sound absorption characteristic of open-cell Mg foams were studied. The experimental results indicate that PEO coating is mainly composed of a mixture of MgO and MgAl2O4 ceramics with high hardness and high brittleness. The compressive strength and the energy absorption capacity of Mg foams improved after being subjected to PEO treatment; however, the brittleness of the PEO-coated foams was more noticeable than that of the uncoated foams. The sound absorption coefficient of the PEO-coated Mg foams is slightly greater than that of the uncoated foams, which is mainly attributed to increased viscous friction induced by the micro-pores in the PEO coatings.

In this study, open-cell Mg composite foams reinforced with in-situ Mg2Si were prepared. In order to refine the Mg2Si compound, the composite foams were co-modified with Y + Sb elements followed by solution heat treatment. The influences of complex modification and holding time of solution heat treatment on the microstructure and compressive properties of the composite foams were studied. The experimental results show that the morphology of Mg2Si is effectively changed by complex modification. The coarse dendritic primary Mg2Si (∼40 μm) is altered to the fine polygonal shape (∼10 μm); the coarse eutectic Mg2Si is transformed to a long rod or granular shape. Both compressive strength and energy absorption capacity of the composite foams are significantly increased. Additionally, with the increasing holding time of solution heat treatment, the eutectic Mg2Si undergoes obvious spheroidization, and the corner of the primary Mg2Si occurs passivation. Consequently, the compressive strength and energy absorption capacity are further improved.