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在超塑性变形过程中对Al-6%(重量)Mg合金试样内部空洞的形貌、分布和大小等进行了观察分析,表明截面变形最大的部位,其空洞容积(V)的百分含量及空洞平均半径(r)也最大。空洞对应变速率也很敏感,提高应变速率,V和r值均随之下降。计算表明,空洞扩散成长方式转换至指数定律成长方式的临界空洞半径(r_c)为2.4μm。当r>r_c时,[dr/dε]_p随着r的提高而迅速提高。根据实验结果,提出了超塑性材料对空洞容积百分含量的容忍度概念。并得出该材料在773K、ε=1.67×10_(-4)S_(-1)时的拉伸变形,其容忍度为V_t=18%。
In the process of superplastic deformation, the morphology, distribution and size of cavities in Al-6% Mg alloy samples were observed and analyzed. The results showed that the percentage of void volume (V) And the average hole radius (r) is also the largest. Void is also very sensitive to strain rate, increasing the strain rate, V and r values are decreased. Calculations show that the critical cavity radius (r_c) of the growth mode of void diffusion growth to exponential growth is 2.4 μm. When r> r_c, [dr / dε] _p increases rapidly with r. According to the experimental results, the concept of tolerance of superplastic material to void volume percentage is proposed. The tensile deformation of the material at 773K, ε = 1.67 × 10_ (-4) S _ (- 1) is obtained, and its tolerance is V_t = 18%.