回复态超纯铝大变形组织与强化机理的研究

Study on Microstructure and Strengthening Mechanism of Recovered Ultra Pure Aluminum with Large Deformation

采用X射线衍射(XRD)分析、电子背散射衍射(EBSD)分析技术以及拉伸实验,研究了回复态(锻造+250℃×24 h热处理)超纯铝在大变形(等通道转角挤压+压缩)过程中的组织演变及强化机理。结果表明:回复态超纯铝的低角度晶界数目占比为99.7%,后续大变形过程中发生动态连续再结晶,部分低角度晶界变成大角度晶界,平均角度增大,位错密度基本不变。超纯铝由于其内部钉扎大应变过程中位错因素很少,其不能有效累积位错,进而不能产生位错强化。大变形引入的位错运动到低角度晶界,被其吸收,低角度晶界长大。回复态大变形超纯铝的强化主要是低角度晶界强化、晶格摩擦应力以及高角度晶界强化,其中主要强化是低角度晶界强化。

Microstructure evolution and strengthening mechanism of recovered ultra pure aluminum （forging ＋heat treatment of 250 ℃×24 h） during large deformation （equal channel angular pressing＋compressing） were investigated by X-ray diffraction （XRD）, electron backscattered diffraction （EBSD） analysis and tensile test. The results indicate that the low angle grain boundary of recovered ultra pure aluminum accounts for 99.7%, and the dynamic continuous recrystallization occurs in the subsequent large deformation process, partial low angle grain boundaries become large angle grain boundaries, the average angle increases,and dislocation density is basically invariant. Because of its very few dislocations factors in the pinning large strain process, ultra pure aluminum can not effectively accumulate dislocation, thus the dislocation strengthening can not be produced. Dislocation with large deformation moves into the low angle grain boundaries, which is absorbed by it, and low angle grain boundaries grow. The strengthening of the super pure aluminum in the large deformation of recovery state is mainly the low angle grain boundary strengthening, the lattice friction stress and the high angle grain boundary strengthening, in which the main strengthening is the low angle grain boundary strengthening.