Abstract

In this work, microstructure, mechanical properties and fracture behavior of the magnesium/steel bimetal using compound casting assisted with hot-dip aluminizing were investigated, and the interface bonding mechanism of the magnesium/steel bimetal were also analyzed. The results indicate that the magnesium/steel bimetal obtained without hot-dip aluminizing had larger gaps through the whole interface without reaction layers between magnesium and steel, leading to a poor mechanical bonding. After the steel substrate was hot-dip aluminized, an intermetallic layer along with an Al topcoat layer were formed on the surface of the steel substrate, and the intermetallic layer was constituted by Fe₂Al₅, τ₁₀-Al₉Fe₄Si₃, FeAl₃ and τ₆-Al_4.5FeSi phases. In the case of the magnesium/steel bimetal obtained with hot-dip aluminizing, a compact and uniform interface layer with an average thickness of about 17 μm that consisted of Fe₂Al₅, τ₁₀-Al₉Fe₄Si₃, FeAl₃ and Al₁₂Mg₁₇ intermetallic compounds was formed between the magnesium and the steel, obtaining a superior metallurgical bonding. The interface layer had much higher nano-hardnesses compared to the magnesium and steel matrixes, and its average nano-hardness was up to 11.1 GPa, while there were respectively 1.1 and 4.2 GPa for the magnesium and steel matrixes. The shear strength of the magnesium/steel bimetal with hot-dip aluminizing reached to 23.3 MPa, which increased by 8.59 times than that of the composites without hot-dip aluminizing. The fracture of the magnesium/steel bimetal with hot-dip aluminizing represented a brittle fracture nature, initiating from the interface layer.

Graphic Abstract

中文翻译：

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热浸渗铝复合铸造镁/钢双金属组织、力学性能及断裂行为

摘要

本文研究了热浸镀铝复合铸造镁/钢双金属的显微组织、力学性能和断裂行为，并分析了镁/钢双金属的界面结合机理。结果表明，未经热浸镀铝获得的镁/钢双金属在整个界面上具有较大的间隙，镁与钢之间没有反应层，导致机械结合不良。钢基体热浸镀铝后，在钢基体表面形成金属间层和Al面漆层，金属间层由Fe ₂ Al ₅ , τ ₁₀ -Al ₉ Fe ₄ Si构成₃、FeAl ₃和τ ₆ -Al _4.5 FeSi相。在通过热浸镀铝获得的镁/钢双金属的情况下，由 Fe ₂ Al ₅ , τ ₁₀ -Al ₉ Fe ₄ Si ₃ , FeAl ₃组成的平均厚度约为 17 μm 的致密均匀的界面层和 Al ₁₂ Mg ₁₇镁和钢之间形成金属间化合物，获得了优良的冶金结合。与镁基体和钢基体相比，界面层具有更高的纳米硬度，其平均纳米硬度高达 11.1 GPa，而镁基体和钢基体的平均纳米硬度分别为 1.1 和 4.2 GPa。热浸镀铝镁/钢双金属的剪切强度达到23.3 MPa，比未热浸镀铝的复合材料提高了8.59倍。镁/钢双金属与热浸镀铝的断裂代表了脆性断裂性质，从界面层开始。

图形摘要