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Influence of Heat Treatment on the Microstructure and Corrosion Behavior of Thixo-cast Mg-Y-Nd-Zr
Journal of Materials Engineering and Performance ( IF 2.3 ) Pub Date : 2020-09-10 , DOI: 10.1007/s11665-020-05085-1
Z. Szklarz , Ł. Rogal

The influence of semisolid metal processing (SSM, also called thixoforming) and T6 heat treatment (HT) on the microstructure and corrosion behavior in chlorides of Mg-Y-Nd-Zr (WE43B) magnesium alloy was investigated. The as-cast microstructure is composed of α-Mg grains with the size of 52.8 ± 1.9 μm surrounded by eutectic precipitations enriched in rare-earth elements (Y, Nd). The thixo-cast microstructure contained α-Mg globular grains with the size of 65.5 ± 2.1 μm surrounded by a fine eutectic mixture in the volume of 26.6%. The T6 HT (heat treatment and saturation at 525°C/5 h, cooling in H2O and aging at 190°C/48 h) caused an increase of yield strength to 180 MPa and tensile strength to 280 MPa at the hardness 105 ± 4 HV5. Next, the electrochemical response was investigated in 0.1 M NaCl using the global and local LSV (linear sweep voltammetry) and EIS (electrochemical impedance spectroscopy) methods. The EIS method suggests the same mechanism for the processes occurring at the electrode/electrolyte interface and shows higher values of the polarization resistances of treated samples after 24-h immersion tests. In particular, better corrosion resistance in chlorides is observed in the alloy after SSM compared to the SSM/HT specimen, which has also been confirmed by the LSV tests performed after 24-h immersion. By using a local technique, a higher susceptibility of the matrix of SSM and SSM/HT samples to pitting corrosion has been revealed.



中文翻译:

热处理对触变铸造Mg-Y-Nd-Zr显微组织和腐蚀行为的影响

研究了半固态金属加工(SSM,也称为触变性)和T6热处理(HT)对Mg-Y-Nd-Zr(WE43B)镁合金的氯化物的组织和腐蚀行为的影响。铸态组织由尺寸为52.8±1.9μm的α-Mg晶粒组成,周围是富集稀土元素(Y,Nd)的共晶沉淀。触变铸造的微观结构包含尺寸为65.5±2.1μm的α-Mg球状颗粒,周围是体积为26.6%的精细共晶混合物。T6 HT(在525°C / 5 h时进行热处理和饱和,在H 2 O中冷却并在190°C / 48 h时效)在硬度105时导致屈服强度增加到180 MPa,抗拉强度增加到280 MPa。 ±4高压5。接下来,使用整体和局部LSV(线性扫描伏安法)和EIS(电化学阻抗谱)方法研究了在0.1 M NaCl中的电化学响应。EIS方法建议在电极/电解质界面处发生的过程具有相同的机理,并且在24小时的浸没测试后显示出较高的处理样品极化电阻值。尤其是,与SSM / HT试样相比,SSM试样在合金中观察到的氯化物具有更好的耐腐蚀性,这也被浸泡24小时后进行的LSV试验所证实。通过使用局部技术,已经揭示出SSM和SSM / HT样品的基质对点蚀的敏感性更高。

更新日期:2020-09-11
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