Abstract
Carbon addition was performed for doped molybdenum having two kinds of grain structures, large and elongated grain structure and relatively small and elongated grain structure. The three-point bend tests were performed for these samples. In this study low-temperature fracture strength and ductility was represented by two parameters; critical stress and critical temperature respectively. Then their fracture surfaces were examined by using a scanning electron microscopy, and crack generation and propagation characteristics were investigated.
The fracture strength of doped molybdenum was generally improved by a small addition of carbon, but the mechanism of improvement was different depending on the grain structure. In case of large and elongated grain structure, the increase of strength was attributed to the strengthening of the small grain (s), which was identified as the crack generation site. On the other hand, in case of relatively small and elongated grain structure the increase of strength was attributed to the strengthening of the whole grain boundaries. The ductility of doped molybdenum was also improved by a small addition of carbon. This result was mainly attributed to the increase of the fracture strength.
