PRE-MACRO YIELD REGION IN IRON

被引:24
作者
BERNSTEIN, IM
机构
[1] Edgar C. Bain Laboratory for Fundamental Research, United States Steel Corporation Research Center, Monroeville
来源
ACTA METALLURGICA | 1969年 / 17卷 / 03期
关键词
D O I
10.1016/0001-6160(69)90065-0
中图分类号
TF [冶金工业];
学科分类号
0806 ;
摘要
The plastic strain region from ~3 × 10-5 through macroscopic yielding was examined in Ferrovac-E iron from room temperature to 77°K. By analyzing the stress-strain curve in the pre-macro yield region, the variation of the true plastic strain rate with stress was obtained. Such information was used to emphasize that the term proportional limit has little physical significance unless it is defied for a known plastic strain rate. It was further demonstrated that for annealed and unprestrained materials, the temperature dependence of the proportional limit, defined at constant strain rate, is the same as for the lower yield stress. By applying the concept of dislocation dynamics, the increasing stress in the pre-macro yield region was shown to be due primarily to the increase in velocity of a constant density of mobile dislocations. This analysis also provides the best indirect method to date of obtaining the velocity stress exponent, m*, over a wide range of temperatures. The values so obtained satisfy the thermodynamic criteria of thermally activated deformation, that the product m*T is constant at low temperatures. © 1969.
引用
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页码:249 / +
页数:1
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