Corrosion behavior of Mg-Gd-Zn based alloys in aqueous NaCl solution

The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phase.The morphology of the second phase at the grain boundary differed in both alloys:it was a continuous network structure in Mg-10Gd-6Zn,whereas it was relatively discrete in Mg-10Gd-2Zn.The dendrites were finer in size and highly branched in Mg-10Gd-6Zn.The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn alloys.Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode,however,filiform corrosion dominated in the later stage,which was facilitated by the LPSO phase in the matrix.Severe micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second phase.The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times.Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times,and was removed by the chromic acid used for the corrosion product removal.

Microstructural, mechanical and corrosion characterization of an as-cast Mg-3Zn-0.4Ca alloy for biomedical applications

The as-cast Mg-3Zn-0.4Ca alloy shows a great potential to be used in biomedical applications due to its composition,mechanical properties and biodegradability.Zn and Ca appear naturally in the organism accomplishing vital functions.The alloy consists of an a-Mg matrix and a eutectic composed of a-Mg4-Ca2Mg6Zn3.The eutectic product enhances the mechanical properties of the studied alloy,causing strengthening and providing superior hardness values.In this alloy,cracks initiate at the intermetallic compounds and progress through the matrix because of the open network formed by the eutectics.Attending to the corrosion results,the eutectic product presents a noble potential compared to the a-Mg phase.For this reason,the corrosion progresses preferentially through the matrix,avoiding the(α-Mg+Ca2Mg6Zri3)eutectic product,when the alloy is in direct contact to Hank's solution.

添加合金化元素对铸态Mg-Sn-Ca合金的显微组织和力学性能的影响(英文)

在铸态Mg-Sn-Ca （TX系列）合金中添加不同含量的Sn、Ca、Al、Si和Zn等合金化元素，研究其在25~250°C温度范围内的压缩强度和显微组织变化。当合金中Sn/Ca质量比到达2.5时，在晶界处有Mg2Ca相生成；而当Sn/Ca质量比为3时，合金基体中只有CaMgSn相存在。当Sn/Ca质量比在2.5以上时，合金的压缩强度随着温度的升高而降低，在100~1750°C保持基本不变，这主要是由于生成的Mg2Ca相的强化作用所致。然而，当Sn/Ca质量比为3时，合金的强度较低，且随着温度的升高而下降更快。在这些合金中，Mg-3Sn-2Ca合金的强度最高。向其中添加0.4%Al会导致其强度增加，然而同时添加Si会导致强度下降。同样地，添加Zn也能够提高合金的强度，而同时添加Al会导致强度下降。导致合金强度变化的原因与合金中生成的各种金属间化合物有关。

Electrochemical behavior of magnesium alloys in simulated body fluids

Potentiodynamic electrochemical technique was utilized to study the corrosion behavior of magnesium alloys in simulated body fluids(SBFs). The influence of materials,solutions and their temperature on corrosion rate was mainly discussed. The results demonstrate that the free corrosion potential(Ecorr) of AZ31 and AZ91 alloys rises rapidly at initial stage,and then stabilizes at some value. Ecorr of WE43 alloy increases continuously. While Ecorr of AZ91 alloy with macro-arc oxidation(MAO) coating decreases drastically in 3 min,and then fluctuates between -1 607 mV and -1 503 mV. The WE43 alloy has better corrosion resistance in Hank's solution,compared with AZ31 and AZ91 alloys. Corrosion rates of the alloys are sensitive to the chemical composition and temperature of SBFs. A thin MgF2 film slightly improves corrosion resistance. An MAO coating on AZ91 alloy significantly reduces corrosion rate and enhances Ecorr. Pitting corrosion occurs on both AZ31 and WE43 alloys in Hank's solution.

Bulk and local textures of pure magnesium processed by rotary swaging

Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed a combination of different components such as {00.2} basal fibre and two weak {10.0} and {11.0} fibres. Asymmetric distribution of the basal fibre around swaging direction was observed and being related to the processing parameters. Texture gradient analysis by synchrotron radiation demonstrates a non-uniform deformation of the RS processed pure Mg from surface to the centre.

Mg-4Al-2Ba-2Ca(ABaX422)合金的热锻及热加工图的构建（英文）

将Mg-4Al-2Ba-2Ca(ABa X422)合金在300~500°C的温度范围内、0.01~10 mm/s的加工速率下热锻成杯型件,构建其热加工图,并研究其显微组织的演变。采用有限元法对该工艺进行模拟,估计加工余量的局部应变速率和平均应变速率范围。热加工图存在以下2个区域:(1)300~390°C,0.0003~0.001 s^(-1);(2)400~500°C,0.0003~0.3 s^(-1);这2个区域都存在动态再结晶(DRX)。该图表明,在高应变速率和低于400°C的温度下存在大范围的流动失稳区,在此区域会发生流动局部化。在上述2个区域条件下制备的锻件完好且组织均匀,在第一个区域条件下锻造所获锻件的晶粒尺寸更小。然而,当在流动失稳区锻造时,合金在最终成形前发生断裂。实验结果表明,上述2个区域条件下的荷载-行程曲线与模拟曲线吻合较好,而在失稳区获得的曲线则不平坦。