APFIM Characterization of Grain Boundary Segregation in Titanium

Abstract. The grain boundary segregation behavior of titanium and carbon have been characterized in two titanium carbide-doped molybdenum alloys. The matrix of these alloys was found to be significantly depleted in titanium, carbon, oxygen, and nitrogen. Both titanium oxycarbide and molydenum carbide precipitates were observed. The Gibbsian Interfacial Excess, Ti, determined from atom probe analyses revealed significant enrichments of carbon and nitrogen at the grain boundaries in both alloys. In atom probe analyses where the carbon level was high at the grain boundary, the oxygen level was below the detection level and donversely, in analyses where the carbon level was low, some oxygen was detected and suggests that carbon has a beneficial effect of displacing the oxygen from the grain boundary. 1