通过X射线衍射分析(XRD)、电子背散射衍射分析(EBSD)分析技术表征大应变后材料内部微观结构,并结合拉伸实验通过公式定量计算出各部分强化因素对合金屈服强度的贡献,研究了锻造及退火态铝镁单相合金(Al-1.5％ Mg)在大变形过程中的组织演变及强化机制.结果表明:由于固溶镁元素的存在,铝镁单相合金在大变形过程能有效累积位错.等通道转角大应变加工使得平均晶粒尺寸减小(4.605 μm降低至2.183 μm),平均晶界角度提高(4.43°提高至6.51°),低角度晶界比例减少(0.97降低至0.89),晶体取向显著降低.后续的压缩大应变加工进一步降低平均晶粒尺寸(2.183 μm降低至1.328 μm),提高高角度晶界的比例(0.10提高至0.16).大应变铝镁合金的强化主要由晶格摩擦应力、位错强化、低角度晶界强化、高角度晶界强化和固溶强化组成,其中位错强化和低角度晶界强化贡献占绝大部分.
The internal microstructure of the materials after large strains was characterized by X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) analysis techniques,and tensile tests was combined to calculate the contribution of each strengthening factors on the yield strength of the alloy by quantitative formula.The microstructure evolution and strengthening mechanism of Al-1.5％ Mg single-phase alloy in as-cast and as-annealed states during large deformation were investigated.Results indicated that because of the presence of Mg in the alloy,large deformation could effectively accumulate dislocations.Average grain size(from 4.605 μm to 2.183 μm),low angle grain boundary (from 0.97 to 0.89) and crystal orientation of Al-1.5％ Mg showed a reduction after processed by equal channel angular pressing,with average grain boundary angles being improved (from 4.43° to 6.51 °).The subsequent compression processing further reduced the average grain size (from 2.183 to 1.328 μm),and the proportion of high angle grain boundary increased (from 0.10 to 0.16).Strengthening contributions of large strain Al-1.5％ Mg were mainly from lattice friction stress,dislocation strengthening,low and high angle grain boundary strengthening and solid solution strengthening,and the low angle grain boundary and dislocation strengthening was dominant.
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