Structural inhomogeneity in invar alloys studied by positron annihilation

Abstract

The influence is studied of a plastic deformation on the angular correlation of the annihilation radiation from iron‐nickel alloys. The results obtained confirm earlier conclusions that the anomalies of the effect in the invar FeNi alloys are associated with microscopic structural inhomogeneities. It is suggested that the inhomogeneities are the regions of increased iron concentration. Some conclusions are made concerning their properties. Various mechanism of the positron interaction with inhomogeneities are discussed. Study of the Fe75.2Pt24.8 invar alloys does not show the existence of such inhomogeneities in this alloy. A comparison of the angular correlation curves of Fe31.1Ni68.9 and Fe75.2Pt24.8 alloys shows that in these alloys the positrons are localized near the Fe atoms and do not annihilate noticeably with the localized electrons of the Pt atoms.