Effect of Tic Addition on the Intergranular Brittleness in Molybdenum

Abstract

In searching the elements to suppress the intergranular brittleness in molybdenum, TiC addition was found effective. In order to clarify the effect of TiC addition quantitatively, molybdenum bicrystals containing 1.5 mol%TiC were prepared by a floating zone melt technique. The fracture behaviour was measured by a 4-point bending test at temperatures from 77 K to room temperature and the grain boundaries were observed by scanning and transmission electron microscopy. The results were compared with those for high-purity bicrystals and single crystals. The grain boundary studied was the intrinsically weakest ⟨110⟩ twist boundary with a misorientation angle of 34 degrees. It is shown that the TiC addition decreases the ductile-brittle transition temperature (DBTT) of bicrystals by about 80 K and increases the ductility, though it slightly increases the DBTT of single crystals due to solution hardening. The effect of TiC addition is discussed in connection with grain boundary precipitates. © 1989, The Japan Institute of Metals. All rights reserved.