Separation of second phase particles in spheroidized 1045 steel, Cu-0.6pct Cr alloy, and maraging steel in plastic straining

Experiments were performed on spheroidized 1045 steel, Cu-0.6 pct Cr alloy, and maraging steel containing respectively Fe₃C, Cu-Cr, and TiC particles of nearly equiaxed shape. The local interfacial stresses for separation of these particles during plastic deformation were evaluated by the methods described in the two preceding papers. The results show that the interfacial strengths for these particles in their respective matrices are 242, 144, and 264 ksi. In the spheroidized steel the average diam of the separated particles is distinctly larger than the average diam of the whole population. This is quantitatively explained by the enhanced interfacial stresses developed in regions of above average volume fraction of second phase which frequently occur in very dense populations of particles. No such effect was observed in the other two systems which is consistent with their much lower volume fraction of second phase. Some tension experiments have also been performed with the spheroidized 1045 steel at elevated temperature, giving results qualitatively similar to those at room temperature. This work has been presented in part orally at the Third International Conference on Fracture in Munich, Germany, April 1973.