Effects of Compressive Stress at Elevated Temperatures and Degree of Cold Work on Recrystallization of Metals

The effects of not only degree of cold work but also strain at heating on recrystallization of metals were investigated. First, by comparing the behaviours of secondary recrystallization of Armco iron specimens which were heated freely with those heated under the compressive stress, it was recognized that the secondary recrystallization temperature of Armco iron was reduced by the compressive stress at elevated temperatures. By the hot stage microscopy of the vacuum melted copper specimens compressed to various degrees at room temperature, it was also recognized that the secondary recrystallization temperature was reduced by cold work.Next, the effects of degree of coldw ork on the recrystallization at weld heat-affected zone received the thermal cycle which had characteristics of rapid heating and cooling, were studied after welding actually some kinds of metal specimens cold worked to various degrees.The results obtained were as follows:1) The larger the degree of cold work in aluminum specimens was, the smaller was the size of recrystallized grain at heat-affected zone, except 5% degree of cold work.2) The size of recrystallized grain at coarse grain part of heat-affected zone in stainless steel specimens cold worked to any degree, was always larger than that of 0% degree of cold work. However, the size of recrystallized grain at fine grain part in specimens cold worked to any degree, was always smaller than that of 0% degree of cold work, except 5% degree of cold work.3) On the contrary, the difference of size of recrystallized grain in the various degrees of cold work in mild steel specimens which underwent α-γ transformation, was not recognized.4) The larger the degree of cold work in aluminum and stainless steel specimens was, the larger the width of recrystallized zone at heat-affected zone became.5) However, any change of the width of recrystallized zone at heat-affected zone in mild steel specimens cold worked more than 15% was hardly recognized.