Formation of amorphous and crystalline phases in the ion beam modified boron-iron system studied by Mössbauer spectroscopy

Abstract

Modifications of α-iron by ion implantation of boron ions and ion beam mixing (IBM) at the B-Fe interface were studied by transmission Mössbauer spectroscopy (TMS) and conversion electron Mössbauer spectroscopy (CEMS). Different fluences of 30 keV B + ions were implanted at both room temperature and liquid nitrogen temperature. For comparison, ion implantation at room temperature was performed with an ion energy of 60 keV. The Mössbauer spectra revealed the formation of amorphous phases with a composition similar to that of amorphous films obtained by sputter deposition. Ion implantation at liquid nitrogen temperature increased the amorphous fraction. The annealing behaviour was studied from liquid nitrogen temperature up to about 700 K. Crystallization of the amorphous phases occurred between 373 and 573 K. Deposition of boron layers onto iron samples followed by 120 keV Ar + ion beam mixing at room temperature was studied by CEMS. The spectra again showed the formation of amorphous iron-boron phases but with a higher boron concentration than after ion implantation with the same fluence. The results contribute to the understanding of wear reduction in iron and steels by boron ion implantation and ion beam mixed boron films.