材料期刊网

本文采用自行设计和改进的滚动刀口径向引伸仪,精确地测定了若干典型金属材料的真应力(σ)-真应变(ε)曲线。根据最大均匀应变ε_B对应于σ-ε曲线和dσ/1dε-ε曲线交点的理论关系,探讨了基体和第二相对这两条曲线,亦即对ε_B值的影响。根据在双对数坐标上硬化曲线出现阶段性的事实,分析了硬化指数n_1,n_2对基体和第二相敏感的问题。研究表明,dσ/dε-ε曲线主要取决于基体状态,而口σ-ε曲线则受第二相影响较大。n_1对基体较敏感;n_z则对第二相较敏感。n_s的出现是一个值得重视的问题。文中最后讨论了n和ε_B的关系,指出一定条件下只存在n_z=ε_B的近似关系。

The true stress-strain curves of certain typical metals have been measured precisely with a diametrical extensometer improved by authors. According to the theoretical relationship which the ultimate uniform strain ε_B corresponds to the intersection of the flow stress curve and the rate of strain hardening curve, the effect of matrix and second phase on these two curves, i. e., on the ε_B has been investigated. Preliminary results have demonstrated that the dσ/dε νs e curve mainly depends on the matrix while the σ νs e curve is sensitive to the second phase.The strain hardening curve of a material obeying power hardening relation can be divided into three stages in a lg-lg plot except yielding stage. Thus, there are 3 strain hardening exponents n_1, n_2, n_3 and two knee strains ε_1, ε_2. It shows that n_1 is sensitive to the matrix state while n_2 is sensitive to the second phase. The existance of n_3 is a problem to be worth notice. Since there are several stages on the strain hardening curve the relation n=ε_B can not be established. It has shown that only those metals with high stacking fault energy can nearly suit with the relation n_2=ε_B under the condition ε_1<ε_B.