Shen Zhigang, Wu Zhisheng, Wang Ting, Jia Tuosheng, Liu Cuirong
School of Materials Science and Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, China.
State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology at Weihai, Weihai 264209, China.
Materials (Basel). 2023 Oct 21;16(20):6801. doi: 10.3390/ma16206801.
In this study, 7075 aluminum alloy welding wire with TiB nanoparticle reinforcement as an additive together with the variable polarity TIG welding arc as a heat source were applied to produce thin-walled deposited layer samples. Results indicated that the performance of the deposited structure of 7075 aluminum alloy with a TiB reinforcement phase was significantly improved compared to the deposited structure of ordinary 7075 aluminum alloy welding wire. Meanwhile, the precipitation of the TiB reinforcement phase was insufficient within the structure, and the enhancing effect could not be fully exerted. Moreover, the 7-series aluminum alloy contained a large amount of Zn and Mg elements inside. If the soluble crystalline phase was not fully dissolved, severe stress corrosion could be caused, which inevitably led to a decrease in the mechanical properties. To further improve the performance of the deposited layer, a T6 heat treatment process was performed at 470 °C for 2 h, followed by rapid cooling with distilled water and artificial aging at 120 °C for 24 h. After heat treatment, many second phases appeared in the microstructure of the deposited layer, and the tensile strength increased from (361.8 ± 4.8) MPa to (510.2 ± 5.4) MPa together with the elongation which increased from (9.5 ± 0.5) % to (10.2 ± 0.4) %. The fracture mode of the fracture was a ductile fracture along grain boundaries. The microhardness increased from (145 ± 5) HV to (190 ± 4) HV and exhibited good corrosion resistance in a 3.5% NaCl solution corrosion test.
在本研究中，以添加有TiB纳米颗粒增强相的7075铝合金焊丝与变极性TIG焊接电弧作为热源，制备薄壁熔敷层试样。结果表明，与普通7075铝合金焊丝的熔敷组织相比，含TiB增强相的7075铝合金熔敷组织性能有显著提高。同时，TiB增强相在组织内析出不充分，增强效果未能充分发挥。此外，7系铝合金内部含有大量的Zn和Mg元素，若固溶结晶相未充分溶解，会引起严重的应力腐蚀，不可避免地导致力学性能下降。为进一步提高熔敷层性能，进行了470℃保温2h的T6热处理工艺，随后用蒸馏水快速冷却，并在120℃人工时效24h。热处理后，熔敷层微观组织中出现大量第二相，抗拉强度从(361.8±4.8)MPa提高到(510.2±5.4)MPa，伸长率从(9.5±0.5)%提高到(10.2±0.4)%。断口断裂模式为沿晶韧性断裂。显微硬度从(145±5)HV提高到(190±4)HV，在3.5%NaCl溶液腐蚀试验中表现出良好的耐蚀性。
