LASER AND ELECTRON BEAM PROCESSING OF AMORPHOUS SURFACE ALLOYS ON CONVENTIONAL CRYSTALLINE METALS

Abstract

During last fifteen years various superior surface characteristics including extremely high corrosion resistance and unique electrocatalytic activity have been found for novel melt-spun ribbon-shaped amorphous alloys. Preparation of those amorphous alloys as surface alloys covering bulk conventional crystalline metals has been eagerly awaited for the purpose of utilizing their superior surface characteristics. This is a review of efforts devoted to developing methods for processing amorphous surface alloys by instantaneous melting of a very restricted volume of the surface by irradiation with a CO₂ laser or electron beam and subsequent self quenching by the cold bulk substrates. Processing of a wide area by these high energy density beams requires heating the previously amorphized phase, which is easily crystallized by heating. Consequently, high energy density beam processing is most difficult among various methods for preparation of thermodynamically metastable amorphous alloys. Nevertheless, various amorphous surface alloys have been successfully prepared. The materials consisting of the amorphous surface alloys and bulk crystalline metals are quite suitable for corrosion resistant materials and electrodes for electrolysis of aqueous solutions. A comparison of CO₂ laser and electron beam processing showed the superiority of the latter to the former because of a significantly shorter processing time.