The amount of solid solution hardening by some elements was investigated using Fe-25 mass％Cr ferritic steel and Austenitic steels. It was revealed that the hardening amount by Austenite-former elements was considerably larger than that by ferrite-former elements in Ferritic steel. Meanwhile the hardening amount by Ferrite-former elements showed higher value in Austenitic steel, which was a reverse tendency to Ferritic steel. The mechanism was discussed from the point of solubility limit of elements. As a result, the good correlation between the hardening amount and solubility limit was found and the predictive expression of the hardening amount from solubility limit was suggested.

Segregation behavior at grain boundary of Mg-Zn(Al)-Ca(Sr) alloys was calculated by using the grain boundary phase model based on the Hillert's parallel tangential construction to Gibbs energy. The correlations between the calculated segregations and literature values of their maximum texture intensity and Erichsen value were investigated. The Zn addition in Mg-Ca alloys kept a certain Ca concentration in hcp phase regardless of Ca₂Mg₆Zn₃ precipitation. The addition of Al and Zn in Mg-Ca alloys promoted the Ca segregation. However, the Al addition in Mg-Ca alloys significantly decreased Ca concentration in hcp phase due to precipitation of Al(Mg)-Ca compound phases. According to the comparison between the calculated segregation (Ca and Sr) and literature values of maximum texture intensity, the Ca and Sr segregation in grain boundary promoted a decrease of texture intensity of the alloys. The decrease of the texture intensity of Mg-Al-Ca and Mg-Zn-Sr alloys were relatively small because of the precipitates formation. The negative correlation coefficient of −0.85 was obtained between the calculated grain boundary segregation of Ca at the rolling temperature and the literature values of maximum texture intensity. It was estimated that the large amount of Ca segregation at grain boundary region in Mg-Zn-Ca alloys is obtained by rolling at just below the melting point of Ca₂Mg₆Zn₃ phase in the three-phase region (hcp, C14 and Ca₂Mg₆Zn₃) on the phase diagram.

To investigate the plastic strain dependence of dislocation velocity, stress relaxation tests with various plastic strains were performed using 590-MPa grade ferrite-bainite steel at room temperature. The amount of the stress drop at both 1.00 s and 6.00 × 10¹ s after the beginning of strain holding increased with the increase of plastic strain. Also, the values of dislocation velocity-stress exponent and dislocation velocity coefficient on various plastic strain were obtained to discuss the plastic strain dependence of dislocation velocity. Although it was reported that the dislocation velocity v in elastic and considerably small plastic region increased with flow stress σ (or effective stress σ_e) and also followed the empirical equation ν=B'σ^m* (or ν=B'σ_e^m*), with constant value of dislocation velocity-stress exponent m* and dislocation velocity coefficient B' (or B), we found that the m* decreased and B increased with the increase of flow stress and plastic strain. Taking the plastic strain dependence of m* and B into account, the dislocation velocity was independent of plastic strain. Furthermore, mobile dislocation density, which was estimated from the value of athermal stress obtained from the stress relaxation test, increased as plastic strain increased.