Effect of MeV ion irradiation on the coefficient of thermal expansion of Fe-Ni Invar alloys: A combinatorial study

The effect of low-dose MeV ion irradiation on the thermal conductivity and coefficient of thermal expansion (CTE) of Fe-Ni alloys has been studied over the entire composition range using a combinatorial method. With our experimental precision of +/- 5%, the thermal conductivity of Fe-Ni alloys is unchanged by 2.3 MeV Ar+ irradiation at a fluence of 1.2 x 10(14) ions cm(-2). The CTE of Fe-Ni Invar alloys with Ni concentrations between 30 and 37 at.% increases significantly upon 2.3 MeV Ar+ irradiation. At the Invar composition of Fe65Ni35, the CTE increases from 0.5 x 10(-6) K-1 before ion irradiation to 4.3 x 10(-6) K-1 after irradiation for an ion fluence of 1.2 x 10(14) ions cm(-2) or, equivalently, 0.1 displacements per atom. We attribute this increase in CTE to changes in atomic short-range order created by ion irradiation. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.