Precipitation kinetics of the phase γ' in Fe-Ni-Cr alloys

The authors investigated the precipitation and coalescence kinetics of the γ'phase in alloy 800, an austenitic steel with 33% Ni, 20% Cr and small amounts of Ti and Al. The results led to a law concerning the variation with temperature, ageing, and chemical composition of the particle size in the γ'phase. This law was used to calculate the variation of the elasticity limit of the alloy due to the formation of the γ'phase. The calculations were based on the theories of interaction of (weakly and strongly coupled) dislocation pairs with coherent particles ordered without constraint; the anisotropy of tension along the dislocation line was taken into account as well as the influence of the deformation induced by the misfit. A comparison with experimental results shows that averaging does not occur until 2x105 h at operating temperatures below 800 K. (orig.)