Showing papers by "Tadashi Maki published in 2004"
TL;DR: In this article, the authors used TEM observation to show that finer cementite is dispersed more uniformly in the rapidly heated lath martensite than in the slowly heated specimen.
Abstract: Lath martensite structures, tempered at various temperatures (723-923 K) were studied by changing heating rates (2 K/s to 1 000 K/s) to the tempering temperature in an alloy steel for machine structural use (SCM435; Fe-0.35C-0.24Si-0.77Mn-1.05Cr-0.17Mo). Hardness of the rapidly heated (at 100 K/s or 1 000 K/s) specimen is larger than that of the slowly heated (at 2 K/s) specimen when tempering temperature and time are the same. Cementite precipitates are formed on high-angle boundaries (prior austenite grain boundary, block and packet boundaries) as well as within laths and at low-angle boundaries (lath boundaries) by tempering. TEM observation has revealed that finer cementite is dispersed more uniformly in the rapidly heated specimen than in the slowly heated specimen. It is considered that the temperature where cementite precipitation starts is raised by increasing the heating rate to tempering temperature, resulting in a higher nucleation rate and a finer dispersion of cementite.
111 citations
TL;DR: In this paper, the effect of matrix recrystallization on the morphology and crystallography of B1-type vanadium carbide (VC) formed in austenite (γ) was studied by transmission electron microscopy.
90 citations
TL;DR: In this article, the microstructures and tensile properties of cold-rolled and annealed pearlite in Fe-0.8mass%C alloys with various contents of Mn and Si were investigated.
Abstract: The microstructures and tensile properties of cold-rolled and annealed pearlite in Fe-0.8mass%C alloys with various contents of Mn and Si were investigated. With the addition of Mn and Si, the tensile strength (TS) and yield strength (YS) of cold-rolled and annealed pearlite were vastly improved, but its effect on ductility of the cold-rolled pearlite is negligible. The addition of Si is quite effective in improving the ductility of cold-rolled and annealed pearlite, especially when the strength is at a higher level, i.e., lower annealing temperature or shorter annealing period. The optimal tensile properties in the alloys with Mn or Si were obtained after annealing at 723 K for short annealing periods (30 to 120 s). The combined addition of Mn and Si is more effective in improving the tensile properties of cold-rolled and annealed pearlite.
29 citations