Effect of sigma phase on thermophysical properties of Fe55Cr45 alloy. (September 2019)

• Record Type: Journal Article
• Authors: Hajra, Raj Narayan; Tripathy, Haraprasanna; Sudha, C.; Vijayashanthi, N.; Raju, S.; Saroja, S.
• Is Part Of: Intermetallics. Volume 112(2019:Sep.)
• Publication Date: 2019-09
• Subjects: Fe-Cr alloy -- Sigma phase -- Thermal expansion -- Thermal conductivity; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2019.106552
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: This paper presents the results of an experimental and modelling study to determine the thermophysical properties of α and σ phases in Fe55 Cr45 (wt%) alloy. A comprehensive analytical model was used to predict the temperature dependent variation of enthalpy and specific heat, which are compared with experimental results. σ phase was synthesized from homogenized α alloy through heat treatment at 973 K for 300 h. Analysis of high temperature phase stability showed a magnetic transformation for α phase at 831 K and σ→α structural transformation for sigma phase at 1120 K with an enthalpy of 2.6 ± 0.2 kJ mol −1 . Room temperature linear thermal expansion coefficient (CTE) for α and σ phases were obtained as 7.39 × 10 −6 and 15.03 × 10 −6 K -1 respectively. While the α phase exhibited an increase of 118% in CTE up to 1000 K, only 1.7% increase was observed for σ phase. Room temperature thermal conductivity for σ was much lower (3.1 W m −1 K −1 ) than that of the α phase (16.22 W m −1 K −1 ). The systematic experimental investigations carried out in the present study, established that formation of σ has an adverse effect on the heat transport properties of structural steels and their welds. Highlights: Effect of intermetallic sigma (σ) phase formation on thermal properties of parent alpha (α) phase of Fe55 Cr45 alloy. Effect of sigma formation on thermal expansion of parent alpha (α) phase. Effect of sigma formation on thermal conductivity of parent alpha (α) phase.