Thermal expansion characteristics of Fe-9Cr-0.12C-0.56Mn-0.24V-1.38W-0.06Ta (wt.%) reduced activation ferritic-martensitic steel

The lattice and bulk thermal expansion behavior of an Indian version of reduced activation ferritic-martensitic (INRAFM) steel has been quantified using high temperature X-ray diffraction and dilatometry. The lattice parameter of tempered a-ferrite phase exhibited a smooth quadratic increase with temperature, while that of gamma-austenite remained fairly linear up to 1273 K. The results suggest that alpha-ferrite + Carbides -> gamma-austenite transformation occurs upon continuous heating in the temperature range, 1146 <= T <= 1173 K. Further, this transformation is found to be accompanied by a reduction in average atomic volume. The mean linear thermal expansion coefficients of tempered alpha-ferrite and gamma-austenite phases are estimated to be about 1.48 x 10(-5) and 2.4 x 10-5 K-1 respectively. The magnetic contribution to relative thermal dilatation (Delta l/l(298))(mag) is found to be small and negative, as compared to phonon contribution. (C) 2015 Elsevier B.V. All rights reserved.