Abstract
The effects of tensile speed and temperature on ky of the Petch equation were studied by obtaining the relation between lower yield stress and tensile speed for low carbon steel of various grain sizes.
The results obtained are summarized as follows:
(1) The Petch slope ky seems to be constant in the low temperature range under a constant tensile speed; it may be explained by the mechanism of dislocations created in the vicinity of the grain boundary. On the other hand, ky decreases with increasing temperature at elevated temperatures; in this range, ky may be a function of unlocking stress and boundary strength.
(2) The ky is dependent upon the tensile speed in the low temperature range where it is independent of temperature. It may be explained from the fact that the friction stress increases with tensile speed. On the other hand, the tensile speed dependence of ky disappears at elevated temperatures. It may be explained from that ky contains both the term of unlocking stress which is affected by the tensile speed and that of boundary strength independent of tensile speed.
