Surface treatment of aluminum by high current pulsed electron beam

Abstract

The development of advanced technology based on the interaction of high current pulsed electron beam (HCPEB) with solid materials is very important at present time [R. Stark, J. Christiansen, et al., IEEE Trans. Plasma Sci. 23 (3) (1995) 258–264; T. Witke, A. Lenk, B. Schultrich, IEEE Trans. Plasma Sci. 24 (1) (1996) 61–62]. When the concentrated electron flux are acting on a material, superfast processes such as heating, melting, and solidification, as well as dynamic stresses induced in the processes impart surface layer with improved physical, chemical and mechanical properties unattainable with conventional surface treatment methods. This paper reports on an investigation on pure aluminum treated by “Nadezhda-2” HCPEB device. The extreme surface is melted to a depth of about 1 μm at the input energy density of 3 J/cm2. Craters, micrometers in size, are formed in the melted surface. Vacancy and dislocations are significantly increased near the surface as a result of the electron bombardment. Based on the microhardness distribution measured on the cross-section, it has been established that the thickness of the modified layer is several hundreds of micrometers beneath the surface, significantly greater than that of the heat-affected zone. The experimental results are compared with those obtained by solving numerically the heat and stress equations, with finite difference and finite element methods, taking into account of the processes of melting and changing of physics parameters related to changing temperature. Satisfactory agreement between experimental and theoretical data is obtained.