ANALYSIS OF MULTICOMPONENT EVAPORATION IN ELECTRON-BEAM MELTING AND REFINING OF TITANIUM-ALLOYS

Experimental evidence and a mathematical model are presented to evalua te the effect of beam-scan frequency on composition change in electron -beam melting of titanium alloys. Experiments characterized the evapor ation rate of commercially pure (CP) titanium and vapor composition ov er titanium alloy with up to 6 wt pet aluminum and 4.5 wt pet vanadium , as a function of beam power, scan frequency; and background pressure . These data and thermal mapping of the hearth melt surface are used t o estimate activity coefficients of aluminum and vanadium in the heart h. The model describes transient heat transfer in the surface of the m elt and provides a means of estimating enhancement of pure titanium ev aporation and change in final aluminum composition due to local heatin g at moderate beam-scan frequencies.