Effect of MeV ion irradiation on the coefficient of thermal expansion of Fe–Ni Invar alloys: A combinatorial study Original Research Article

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 image irradiation at a fluence of image. The CTE of Fe–Ni Invar alloys with Ni concentrations between 30 and 37 at.% increases significantly upon image irradiation. At the Invar composition of image, the CTE increases from image before ion irradiation to image after irradiation for an ion fluence of image or, equivalently, 0.1 displacements per atom. We attribute this increase in CTE to changes in atomic short-range order created by ion irradiation.