新型铝锂合金板材塑性流动与各向异性性能试验研究

摘要

This study is to investigate the formability of a new generation Al-Li-Cu-Mg alloy sheet through uniaxial tensile tests. The yield strength, tensile strength, elongation rate of seven different orientations of the sheet material were obtained. The tension curves of different orientations were plotted and compared to work out the anisotropic index. The constitutive equation of this new Al-Li-Cu-Mg alloy was established on the basis of the tensile test data. The characteristic parameters in Hill48 and Barlat89 yield criteria were calculated through the experiment curves and the yield locus of this Al-Li-Cu-Mg alloy was also obtained. Then, the characteristics of the anisotropic behavior of this alloy during the forming process were analyzed on the basis of the First Strength Theory and the Third Strength Theory. In the end, the cross section of fractured specimens were observed using Scanning Electron Microscopy ( SEM) and the results indicated that, if the elongation rate increases, the population of dimples increases correspondingly, in the contrary, if the elongation rate decreases, more fracture belt were observed. The different features of the fracture along different orientations confirm the significant anisotropy of the material.%通过单向拉伸试验，研究了新型Al－Li－Cu－Mg合金板材的基本成形性能。针对材料显著的各向异性性能，选取屈服强度、抗拉强度、延伸率以及厚向异性指数等材料性能参数进行对比分析，绘制了7个不同取样方向的单向拉伸曲线，研究了材料各向异性的规律。基于对本构方程、各向异性屈服准则的研究及对比，建立了新型Al－Li－Cu－Mg合金的本构模型，并根据实验曲线计算得到 Hill48、Barlat89屈服准则中的各向异性参数，结合各屈服准则绘制了新型Al－Li－Cu－Mg合金屈服轨迹。对比分析各试件的断口方向，并结合第一、第三强度理论，分析了材料的各向异性。利用SEM观察试样的断口形貌，分析对比试件断口的韧窝特征及带状特征。研究发现：试件的延伸率越大，其韧窝特征越明显；反之，其带状特征越明显。从微观角度印证了Al－Li－Cu－Mg合金板材存在的各向异性。