Effect of minor Sc on microstructure and mechanical properties of Al-Zn-Mg-Zr alloy metal-inert gas welds
Effect of minor Sc on microstructure and mechanical properties of Al-Zn-Mg-Zr alloy metal-inert gas welds
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DOI：
10.1016/j.jallcom.2014.11.227
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发表时间：
2015-04-25
影响因子：
6.2
通讯作者：
Yin, Zhimin
中科院分区：
文献类型：
--
作者：
Huang, Xing;Pan, Qinglin;Yin, Zhimin
以Al-Mg-Sc为钎料，对含有微量Sc的2.5 mm厚冷轧Al-Zn-Mg-Zr合金板进行了金属惰性气体（MIG）焊接。采用光学显微镜（OM）、扫描电镜（SEM）、能量色散x射线（EDX）、透射电镜（TEM）、维氏显微硬度试验和室温拉伸试验研究了Sc添加量对焊接接头组织和力学性能的影响。实验结果表明，微量Sc对接头的组织和力学性能有显著影响。在这两种情况下,贱金属由一个典型的纤维结构,不同宽度的各向等大的区域(EQZs)和细粒观察焊缝金属的融合边界,融合区表现出树突微结构和平均尺寸的铝-锌-镁- 0.10% - Sc -锆120μm,在铝-锌-镁- 0.25% - Sc -锆、粒径急剧下降到50μm。造成的晶粒细化主要是极好,相干Al-3 (Sc, Zr)粒子L1(2)结构,它们起着异相成核的作用。观察到的晶粒细化导致熔合区的强度和显微硬度明显提高。Al-Zn-Mg-0.25Sc-Zr合金焊接接头的抗拉强度为460 MPa，比Al-Zn-Mg-0.10Sc-Zr合金焊接接头的抗拉强度提高约11%。熔合区中心的显微硬度由95 HV上升到110 HV。Al-Zn-Mg-Sc-Zr MIG焊接接头的主要强化机制是由eta’析出相引起的析出强化、共格次生Al-3（Sc, Zr）颗粒引起的弥散强化和细晶粒强化。(C) 2015 Elsevier B.V.版权所有
2.5 mm thick cold-rolled Al-Zn-Mg-Zr alloy plates with trace amount of Sc were subjected to metal-inert gas (MIG) welding with Al-Mg-Sc as the filler metal. The influence of Sc additions on microstructure and mechanical properties of the welded joints was investigated by means of optical microscopy (OM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), Vickers micro-hardness test and room temperature tensile test. Experimental results indicated that trace amount of Sc had significant effect on microstructure and mechanical properties of the joints. In both cases, base metal consisted of a typical fiber structure, different width of the equiaxed zones (EQZs) with fine grains were observed in the weld metal at the fusion boundary, fusion zones exhibited dendritic microstructure and average size of Al-Zn-Mg-0.10%Sc-Zr was 120 mu m, while in Al-Zn-Mg-0.25%Sc-Zr, grain size decreased drastically to 50 mu m. The grain refinement is mainly caused by the extremely fine, coherent Al-3(Sc, Zr) particles with L1(2) structure, which act as heterogeneous nucleation. The observed grain refinement resulted in an appreciable increase in fusion zone strength and micro-hardness. Tensile strength of Al-Zn-Mg-0.25Sc-Zr alloy welded joint was 460 MPa, approximately 11% higher than Al-Zn-Mg-0.10Sc-Zr alloy welded joint. Micro-hardness in the center of fusion zone rose from 95 HV to 110 HV. The main strengthening mechanisms of Al-Zn-Mg-Sc-Zr MIG welded joints are precipitation strengthening derived from eta' precipitates, dispersion strengthening and fine grain strengthening caused by coherent secondary Al-3(Sc, Zr) particles. (C) 2015 Elsevier B.V. All rights reserved.