Electrons interaction with matter

A variety of physical processes occur when matter is bombarded by electrons. The main effect of significance for welding and other processes is heat generation. However, EB technology is used for a variety of essentially non-thermal processes in some industries, e.g. radiation curing of composites, cross-linking, paint curing etc.

As electrons interact with the target material, x-rays, secondary electrons, and backscattered electrons are generated. Of these, only the latter is likely to significantly reduce the heat input of the beam for processes of interest, as the others might only amount to one or two percent of the beam energy.

By contrast backscattered electrons can comprise ten or more percent of the beam energy if the substrate is perfectly flat and smooth, and higher losses occur when the substrate material is very dense. However losses are usually in the five to ten percent range on standard engineering surfaces, and lower still as soon as the beam is acting in keyhole mode.

Contact: electronbeam@twi.co.uk

Copyright © 2006 TWI Ltd