1999 Volume 85 Issue 6 Pages 486-491
The effect of B, with the addition of 0.01 and 0.1 mass%, on the spheroidizing behavior of cementite in Fe-0.8mass%C alloy was investigated.
The addition of B accelerated the softening by spheroidizing annealing. This effectiveness was enhanced with the increase in the solution treatment temperature and B content. Spheroidal cementites were most refined when 0.01 mass% B was added. This was attributed to the increase in the number density of nucleation sites which arose from fine cementites equilibrium at solution temperature and coarse cementites precipitated from liquid phase. When the amount of B was increased to 0.1 mass%, the effect of coarse cementites precipitated from liquid phase became significant. This resulted in the increase in the number of coarse spheroidal cementites with the diameter greater than 10 μm, and the decrease in the number of fine spheroidal cementites, supposedly through Ostwald growth mechanism.