Effect of He-ion irradiation on Fe-Cr alloys: M\"ossbauer - effect study

TL;DR

This study investigates how helium ion irradiation affects the atomic and magnetic properties of Fe-Cr alloys, revealing changes in short-range order, hyperfine fields, and magnetization orientation with increasing irradiation dose.

Contribution

It provides detailed insights into the effects of He-ion irradiation on Fe-Cr alloys, including atomic ordering and magnetic property alterations, using Mossbauer spectroscopy.

Findings

Hyperfine field increases with irradiation dose.

Short-range order parameter shifts from clustering to ordering.

Inversion of short-range order occurs at approximately 7 dpa.

Abstract

Effect of He ion irradiation on three model Fe(100-x)Cr(x) alloys (x =5.8, 10.75 and 15.15) was investigated with the conversion electron M\"ossbauer spectroscopy. The study of the alloys irradiated with 25 keV ions revealed that the strongest effect occured in the Fe(84.85)Cr(15.15) sample where an inversion of a short-range-order (SRO) parameter was found. Consequently, the investigation of the influence of the irradiation dose, D, was carried out on the chromium-most concentrated sample showing that the average hyperfine field, <B>, the average angle between the normal to the sample's surface and the magnetization vector, <theta>, as well as the actual distribution of Fe/Cr atoms, as expressed by SRO parameters, strongly depend on D. In particular: (a) <B> increases with D, and its maximum increase corresponds to a decrease of Cr content within the two-shell volume around the probe 57Fe nuclei by ~2.3 at%, <theta> decreases by ~13 degree at maximum, (c) SRO-parameter averaged over the two-shell volume increases with D from weakly negative value (indicative of Cr atoms clustering) to weakly positive value (indicative of Cr atoms ordering). The inversion takes place at D ca. 7 dpa.