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Biodegradable magnesium (Mg) alloy emerges as revolutionary biomaterial by meeting both engineering and medical requirements for implants. In this study, we report a Mg alloy Mg-2.5Nd-0.21Zn-0.44Zr (wt. %, denoted as JDBM) potential for vascular stent application due to its outstanding performance in corrosion behaviors and biocompatibility. The investigation of corrosion properties evaluated by immersion test and electrochemical measurement shows less susceptibility to pitting corrosion and lower corrosion rate of JDBM as compared with AZ31 alloy. The corrosion products of JDBM do not cause significant adverse effect on the cell viability and growth during in vitro cytotoxicity test of the Mg extract via human vascular endothelial cells (HUVECs). We also investigated macrophage response to the Mg extract and observed compromised foreign body reaction (FBR) determined by human peripheral blood derived macrophage fusion and inflammatory cytokine and chemokine secretion. At last, we performed in vivo degradation assessment via implantation of JDBM stent in an animal model, and confirmed long-term stability and structural integrity of the stent in blood vessel. Thus, the JDBM alloy with excellent biocompatibility and long-term stability and durability in vivo, represents a significant advance in the development of biodegradable implants.

We perform a systematic structural investigation of the I-phase particles embedded in Mg matrix in I-phase-reinforced Mg–3.5Zn–0.6Gd alloy and offer evidence to the presence of dislocations in the I-phase particles. Such dislocations are found to be formed on the (0001) plane of Mg matrix, which is attributed to their slipping into the 5-fold and 2-fold planes of I-phase particles. We also discuss how deformation conditions of wrought Mg alloys affect the deformation behaviors of the I-phase and how deformation behavior of I-phase affect the mechanical properties of wrought Mg alloys. The bonding between the I-phase and Mg matrix was also confirmed to be strong.

Bulk metallic glassy composites reinforced by ZrO2 with various volume fraction and particle size were fabricated successfully by spark plasma sintering. The compression test results indicate that mechanical property of composite is related to the particle size and volume fraction of ZrO2. Due to the stress concentration between the ZrO2 and the glassy matrix, both the plastic strain and fracture strength increase firstly and then decrease with the increase of volume fraction of ZrO2. The deformation morphologies of composites after compression reflect the ductile–brittle transition process.

Mg–1.5Zn–0.25Gd (at.%) alloy reinforced by icosahedral quasicrystalline phase (I-phase) was fabricated and subjected to cyclic extrusion and compression (CEC) at 350 °C to investigate the microstructure evolution during CEC and its effect on the mechanical properties. It is observed that, during CEC, the microstructure of the alloy was greatly refined by dynamic recrystallization (DRX), large numbers of I-phase particles precipitated and then grew up, the texture of the alloy was obviously weakened. These changes in microstructure improved the mechanical properties of the alloy significantly and the alloy processed by 8 passes CEC exhibited outstanding plasticity of 31.4% and moderate yield strength of 161 MPa.

In the present study, two kinds of bulk metallic glasses (Zr55Cu30Al10Ni5 and Cu46Zr42Al7Y5) with high strength and no plastic strain were adopted as matrixes. Both of them were reinforced by ductile crystalline TiNb with the same volume fraction and particle size. The compression results showed that the plastic strain of TiNb/Zr55Cu30Al10Ni5 composite was higher 292% than that of TiNb/Cu46Zr42Al7Y5 composite. It should be related to the fracture toughness of the glassy matrix. For the glassy matrix with high toughness, the formation of shear bands and micro-crack at the front of the crack reduced the energy of main crack development. It resulted in a large plastic strain. On the other hand, for the brittle metallic glassy matrix, crack developed quickly through the cross section so that no more shear bands was formed. It resulted in the failure of the sample with smaller plastic strain.

Mg–10Gd–3Y–1.8Zn–0.5Zr (wt.%) (GWZ1032K) alloys are prepared by permanent mold casting at cooling rate of 5 K/s, or further prepared by melt spinning at cooling rate of 104 K/s, or by slow solidification at different cooling rates (0.5 K/s, 0.1 K/s, 0.01 K/s and 0.005 K/s). (Mg,Zn)3RE phase and 14H-LPSO structure in alloys under different conditions are measured by XRD and observed under electron microscope. It shows there is no LPSO structure in the alloy prepared by melt spinning at cooling rate of 104 K/s. In the alloy prepared by permanent mold casting at cooling rate of 5 K/s, fine lamellar 14H-LPSO structure appears in the matrix nearby grain boundaries. With the cooling rates slowing down from 0.5 K/s to 0.005 K/s, (Mg,Zn)3RE phase is gradually replaced by 14H-LPSO phase at grain boundaries, and lamellar 14H-LPSO structure also propagates in α-Mg matrix. Both (Mg,Zn)3RE phase and 14H-LPSO phase are present at grain boundaries in the alloys solidified at cooling rates of 0.5 K/s and 0.1 K/s. When the cooling rate is very slow (0.005 K/s), lamellar 14H-LPSO structure penetrates throughout the matrix grain. It suggests the cooling rate is an important factor for the formation of 14H-LPSO structure in as-cast GWZ1032K alloys. The orientation relationship between (Mg,Zn)3RE phase and 14H-LPSO phase is determined by the composite SAED patterns, which is expressed as (1 1 0)(Mg,Zn)3RE//(0 0 1 4)14H-LPSO phase, [ 3 ¯ 3 2 ] ( Mg , Zn ) 3 RE / / [ 1 1 0 ] 14 H-LPSO phase and [ 1 ¯ 1 2 ] ( Mg , Zn ) 3 RE / / [ 2 1 0 ] 14 H-LPSO phase .

The crystallization behaviors of Mg65Cu25Gd10, Mg65Cu20Ag5Gd10 and Mg65Cu20Ni5Gd10 metallic glasses were compared with respect to the continuous heating and the isothermal annealing. The results showed that both the partial substitution Ag and Ni for Cu in the Mg65Cu25Gd10 glass can increase the activation energy for the first crystallization and however decrease the thermal stability and the crystal growth rate during the isothermal annealing. The difference in the influence on the crystallization behaviors between Ag addition and Ni addition was analyzed in details. The examination of the crystallization product after the isothermal annealing revealed that Ag addition can effectively suppress the formation of the Mg2Cu crystalline phase of Mg65Cu25Gd10 glass while Ni addition can promote the Mg2Cu formation, which is well consistent with the larger glass-forming ability (GFA) of the Mg65Cu20Ag5Gd10 alloy than that of the Mg65Cu20Ni5Gd10 alloy. In addition, the possible relation between the crystallization features with the GFA was discussed.

Mg–Zn–Gd and Mg–Zn–Gd–Cu alloys, reinforced with quasicrystal (I-phase) and Laves phases, have been produced by extrusion process. The deformation behavior of these two alloys at room temperature and at elevated temperatures was investigated, respectively. The Mg–Zn–Gd alloy has high UTS of 305 MPa and elongation of 14.6% due to the strengthening effect of I-phase, while Mg–Zn–Gd–Cu alloy with Laves phases has higher yield stress of 217 MPa due to more strengthening particles and lower elongation of 11.9% resulting from the low content of I-phase and low symmetry of Laves phase due to which it cleaves easily (while the I-phase has a very high symmetry and therefore isotropic in nature). At high temperatures, Mg–Zn–Gd alloy shows large strain due to the excellent plastic compatibility coming from low interfacial energy of I-phase/matrix; Mg–Zn–Gd–Cu alloy has higher level of flow stress, strain exponent and more stable microstructure than Mg–Zn–Gd alloy due to better heat-resistance supplied by collaboration of Laves phases and quasicrystal phase, which can provide more effective pinning effect and suppress grain growth during deformation.

The effect of substitution of Ni for Cu on the glass forming ability and mechanical properties was studied in Mg 65 Cu 25− x Ni x Gd 10 ( x = 0, 5, 10, 15, 20, 25) alloys by thermal analysis and X-ray diffractometry (XRD). With increasing x from 0 to 25 at.%, the glass transition temperature, T g, of Mg 65 Cu 25− x Ni x Gd 10 alloys increases from 417 to 450 K, and the onset temperature of crystallization, T x , decreases slightly, resulting in a decrease in the supercooled liquid region. However, an appropriate substition of Cu by Ni (5 at.%) in Mg 65 Cu 25 Gd 10 significantly improves mechanical properties, especially improves the ductility of Mg-based bulk metallic glass (BMG) while keeping good glass forming ability (GFA). The Mg 65 Cu 20 Ni 5 Gd 10 BMG sample of 5 mm in diameter is fabricated by the conventional Cu-mold casting method in an argon atomsphere.