Microstructure evolution and corrosion behavior of TIG welded joint of a new MgGdNdZnZr alloy during post-weld heat treatment

IF 13.8 1区材料科学 Q1 METALLURGY & METALLURGICAL ENGINEERING

Journal of Magnesium and Alloys Pub Date : 2025-08-01 DOI:10.1016/j.jma.2024.04.019

Xin Tong, Qiman Wang, Guohua Wu, Fangzhou Qi, Junmin Zhan, Liang Zhang

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Abstract

The corrosion behavior of the tungsten inert gas (TIG) welded Mg3Nd3Gd0.2Zn0.5Zr alloy with different post-weld heat treatments was systematically investigated. The results show that the corrosion resistance of the sand-cast base material (BM) was inferior to that of the fusion zone (FZ), which was attributed to the larger grain size and exacerbated galvanic corrosion caused by coarser Mg₃(Nd, Gd) eutectic phases and numerous β precipitates. It is found that post-weld solid-solution (T4) treatment could significantly enhance the corrosion resistance of the joint due to the dissolution of the cathodic second phases and the denser protective film abundant in RE oxides generated in corrosive solution. The precipitation of nanosized phases and ZnZr clusters would slightly increase the susceptibility to localized corrosion of the peak-aged (T6) joint. As the main corrosion products, MgO and Mg(OH)₂ are distributed throughout the whole corrosion film, while RE oxides and RE hydroxides are mainly distributed in the inner layer, which can be explained by inward oxidation and replacement reactions between RE elements and MgO/Mg(OH)₂. Based on the composition and structure of the corrosion product film, a physical model has been proposed for depicting the microstructure evolution associated with the corresponding corrosion behavior of the joints. This work could promote the applications of welded MgRE alloy joint in some corrosion environments.

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新型镁钆钕锌锆合金氩弧焊焊接接头在焊后热处理期间的显微组织演变和腐蚀行为

系统研究了钨惰性气体（TIG）焊接Mg3Nd3Gd0.2Zn0.5Zr合金经不同焊后热处理后的腐蚀行为。结果表明：砂铸基材（BM）的耐蚀性不如熔合区（FZ），这是由于晶粒尺寸较大，Mg3（Nd, Gd）共晶相粗大和大量β析出导致电蚀加剧所致；发现焊后固溶（T4）处理可以显著提高接头的耐蚀性，这是由于腐蚀溶液中生成的丰富的稀土氧化物中阴极第二相的溶解和更致密的保护膜。纳米相和ZnZr团簇的析出会略微增加峰时效（T6）接头的局部腐蚀敏感性。MgO和Mg(OH)2作为主要腐蚀产物分布在整个腐蚀膜中，而RE氧化物和RE氢氧化物主要分布在内层，这可以解释为RE元素与MgO/Mg(OH)2之间的向内氧化和取代反应。基于腐蚀产物膜的组成和结构，提出了一个描述与接头腐蚀行为相关的微观组织演变的物理模型。该工作可促进MgRE合金焊接接头在某些腐蚀环境中的应用。

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来源期刊

Journal of Magnesium and Alloys Engineering-Mechanics of Materials

CiteScore

20.20

自引率

14.80%

发文量

审稿时长

59 days

期刊介绍： The Journal of Magnesium and Alloys serves as a global platform for both theoretical and experimental studies in magnesium science and engineering. It welcomes submissions investigating various scientific and engineering factors impacting the metallurgy, processing, microstructure, properties, and applications of magnesium and alloys. The journal covers all aspects of magnesium and alloy research, including raw materials, alloy casting, extrusion and deformation, corrosion and surface treatment, joining and machining, simulation and modeling, microstructure evolution and mechanical properties, new alloy development, magnesium-based composites, bio-materials and energy materials, applications, and recycling.