目的 研究碾压强化方法对2195-T8铝锂合金搅拌摩擦焊接头组织与力学性能的影响规律,分析微观组织的演变机理,阐明微观组织演变对接头拉伸性能和显微硬度的影响机制。方法 采用专用碾压工具对2195-T8铝锂合金搅拌摩擦焊接头进行碾压处理,利用扫描电子显微镜、电子背散射衍射和万能材料实验机等测试手段分析未碾压及碾压处理后接头的微观组织及力学性能。结果 相比于未碾压接头,经过200 mm/min碾压速度处理后的接头,其平均晶粒尺寸由75.78 μm减小至61.15 μm,块状强化相的最大轴长由0.98 μm减小至0.28 μm,并且强化相的数量增多,接头的抗拉强度由404 MPa增大至442 MPa,搅拌区平均显微硬度从112.5HV提高至121.5HV。然而,由于碾压处理后晶界及强化相数量增多,对位错运动的阻碍作用增强,因此接头延伸率下降。结论 碾压处理可细化2195-T8铝锂合金搅拌摩擦焊接头的晶粒及强化相,增加强化相的数量,从而提高接头的抗拉强度和显微硬度,但同时会降低其延伸率。
Abstract
The work aims to investigate the effect law of rolling treatment on the microstructure and mechanical properties of 2195-T8 Al-Li alloy friction stir welded joints, analyze the evolution mechanism of the microstructure, and elucidate the effect of microstructural evolution on the tensile properties and microhardness of the joints. A specialized rolling tool was used to perform the rolling treatment on the friction stir welded joints of 2195-T8 Al-Li alloy. The microstructure and mechanical properties of the joints before and after rolling treatment were analyzed through scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and a universal testing machine. Compared with the unrolled joint, the joint subjected to rolling at a speed of 200 mm/min exhibited a reduction in average grain size from 75.78 μm to 61.15 μm, and the maximum axial length of the blocky strengthening phases decreased from 0.98 μm to 0.28 μm, and the number of strengthening phases increased. Meanwhile, the tensile strength of the joints increased from 404 MPa to 442 MPa, and the average microhardness in the stir zone increased from 112.5HV to 121.5HV. However, due to the increased number of grain boundaries and strengthening phases after rolling, the hindrance to dislocation movement was enhanced, resulting in a decrease in the joint's elongation. Rolling treatment can refine the grains and strengthening phases of 2195-T8 Al-Li alloy friction stir welded joints and increase the number of strengthening phases, thereby improving the tensile strength and microhardness of the joint, but reducing its elongation at the same time.
关键词
碾压强化 /
铝锂合金 /
搅拌摩擦焊 /
微观组织 /
力学性能
Key words
rolling strengthening /
aluminum-lithium alloy /
friction stir welding /
microstructure /
mechanical property
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基金
国家自然科学基金（52171032）; 河北省自然科学基金（E2023501002）
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