High temperature deformation behavior of bulk cementite produced by mechanical alloying and spark plasma sintering

Using the bulk cementite samples produced by mechanical alloying and spark plasma sintering technique, high temperature deformation behaviors of cementite were studied. To avoid decomposition at high temperature, 5 at.% Mn alloyed cementite ((Fe0.95Mn0.05)3C) was mostly used. Brittle fracture was observed in the bulk cementite when deformed at a high strain rate at elevated temperatures (studied up to 1273 K). However, compression strain (this true strain larger than 2) was observed at around A1 temperature (1000 K) at stresses in the range of 100–150 MPa. Specimens were deformed without cracks and without change in hardness. After this superplastic flow, grains are slightly elongated and grain growth was observed. It was demonstrated that the bulk cementite sheets can be deformed cooperatively with low carbon steel sheets and fine layered cementite/low carbon steel laminates could be fabricated by superplastic deformation. As a possible deformation mechanism of lamellae cementite in pearlite, grain boundary sliding was proposed.