Strain hardening of iron-titanium alloys at very large strains

Abstract

The strain-hardening behavior of a series of irontitanium alloys has been investigated out to large plastic elongations by means of wire drawing. The rate of strain hardening is linear up to the maximum strain reached (∼ 8), and is insensitive to (a) the interstitial level, (b) the “gettering” of the interstitials by titanium, (c) the titanium concentration in solid solution and (d) the presence of a brittle second phase. The strength achieved by wire drawing is a linear function of (d̄) −1, where d̄ is the mean linear intercept between cells walls on a transverse section, as predicted by the Langford-Cohen model for strengthening at large plastic elongations. The frictional stress on this basis is found to be same as that arising from the Hall-Petch equation of grain-size strengthening. The results indicate that, although the strain-hardening rate is insensitive to interstitial and/or alloy content, the dependence of the strengthening on cellular refinement may be affected by these variables. According to the above model, this means that such factors as the dislocation-line tension and the geometry of dislocation glide may be influenced by compositional factors.