The effects of Nd addition on corrosion behavior of Mg66Zn30Ca4 amorphous alloys in simulated body f luids(SBF) were studied in this paper. Electrochemical properties of the samples before and after corrosion were determined. Surface morphologies of samples after immersion in SBF at 37℃ for different times were observed under scanning electron microscope(SEM). Results show that the corrosion resistance of Mg-based alloys in SBF is improved with the addition of Nd element. The electrochemical properties indicate that microalloying Nd element to the alloys leads to an ennoblement in the open circuit potentials of the alloys and a decrease in the anodic current density in SBF, especially for the Mg66-xZn30Ca4 Ndx alloys with Nd content of 1.0at.%-1.5at.%. It was observed that the surface morphologies of the alloys immersed in SBF change with the Nd addition. A f lakelike structure parallel to the alloy substrate formed on the surface of 1.0at.% Nd-containing alloy immersed in SBF for 7 days improves the corrosion resistance of the amorphous alloys by blocking the corrosion liquid from attacking the alloys.
Metallic glasses(MG)represent an interesting group of materials as they possess outstanding physical,chemical and mechanical properties compared to their crystalline counterparts.This paper reviews the synergistic influence of Ni and Nb elements on thermal stability of supercooled liquid and corrosion resistance of as-cast Cu-Zr(Hf)-Ti-Ni-Nb bulk metallic glasses(BMGs).Additionally,in-situ second phase reinforced Cu-based BMG composites with high corrosion resistance and excellent mechanical properties are investigated.On the other hand,this paper reports the development of ultra-high corrosion resistant Ni-based metallic glasses at high temperatures for their potential applications.Corrosion resistance and XPS analysis of the Nifree Ti-based BMG are also introduced.
In our current work,AZ31 magnesium alloy foams with closed-cell were successfully fabricated by melt foaming method using Ca and CaCO3 as thickening and blowing agent,respectively.The influences of porosity and pore size on the quasi-static compressive properties of the foams were systematically investigated.The results showed that the yield strength,energy absorption capacity and ideality energy absorption efficiency were decreased with the increase in porosity.However,specimens with porosities of 60%,65%and 70%possessed similar total energy absorption capacity and ideality energy absorption efficiency.Meanwhile,experimental results showed that mean plateau strength of the foams was increased first and then decreased with increase in mean pore size.In addition,energy absorption capacities were almost the same in the initial stage,while the differences were obvious in the middle stage.From the engineering point of view,the specimens with mean pore size of 1.5 mm possess good combination of mean plateau strength and energy absorption characteristics under the present conditions.
Mg-Zn-Y-based quasi-crystal (QC) alloys were fabricated by pouring melts into different cooling media. The effects of different cooling rates on the QC morphology, size, volume fraction and micro-hardness were studied. Multi-component Mg-Zn-Y-based QC alloys were synthesized based on amorphous design principle. QC morphology transformation and its influencing factors were analyzed. Micro/nano spherical quasi-crystals (QCs) were fabricated through a wedge-shaped copper mould and their forming mechanism were discussed by atoms cluster theory, optimum cooling rate theory and the known crucial criteria. The results of research show that with the cooling rate reduced, the solidified morphology of QC phase changes from near-spherical, micro petals (1 to 2 μm) to big petals (20 μm) and finally grows up to bulk pentagon or hexagon (200 to 400 μm). Multi-component micro-spherical QCs possess higher value of micro-hardness than petal-like QCs with the same components, and also higher than ternary micro-Mg-Zn-Y QCs. The fine master alloys containing micro-QCs (0.4 μm) and nano-QCs (about 300 nm and 40 nm) have been fabricated correspondingly on the middle and the tip of wedge-shaped castings. A morphology evolution schematic diagram of Mg-Zn-Y-based QCs is included in this paper.
