Ductile iron containing 6.16wt% A1 was developed to investigate the effects of aluminum on both its microstructure and hardness. It was found that aluminum not only increases the nodule count and pearlite content but ...Ductile iron containing 6.16wt% A1 was developed to investigate the effects of aluminum on both its microstructure and hardness. It was found that aluminum not only increases the nodule count and pearlite content but also improves the hardness in both sand mold and metal mold castings. Annealing treatments were conducted to attain a homogenous microstructure and improve high-temperature serviceabil- ity. A ferrite/carbide or ferritic matrix was gained depending on the annealing temperature. It is also discovered that annealing has inverse in- fluences on the hardness of the bulk alloy and the ferrite phase. Although it causes a small decrease in the bulk hardness of the specimens, it leads to an increase in the microhardness of the ferrite. Micro-segregation of the alloying elements was also investigated by means of electron probe micro-analysis for the specimens with different annealing durations and the as-cast specimen as well. An optimum annealing time was proposed to result in the least amount of micro-segregation of aluminum and silicon between graphite nodules.展开更多
The purpose of this study was to determine the influence of heat treatment cycle on graphite phase formation on CK 45 steel. The presence of well distributed graphite in the matrix is responsible for the good mechanic...The purpose of this study was to determine the influence of heat treatment cycle on graphite phase formation on CK 45 steel. The presence of well distributed graphite in the matrix is responsible for the good mechanical and thermal properties of this kind of alloy. Such properties include excellent wear resistance, higher resistance to thermal shock, and higher resistance to oxidation at high temperature. A number of specimens were made up of appropriate design to provide the experimental materials. The transformation phase to a free carbon microstructure during graphitization under different conditions was then examined for the most successful experimental steels. Austenitising temperature of 920℃ and the following isothermal heat treatment of 750℃ at different holding times were used. Microstructures were examined by OM （optical microscopy） and SEM （scanning electron microscopy）. Furthermore, it was found that isothermal transformation at 750℃ for different soaking times produced a typical microstructure. Also, the amount of graphite increased with increasing isothermal heat treatment time. Heat treatment leading to supersaturation of iron with carbon was described and some of the consequences of the supersaturation were presented. Finally, the formation of the thermodynamically stable state of the graphite taken from the supersaturated solid solution was discussed.展开更多
文摘Ductile iron containing 6.16wt% A1 was developed to investigate the effects of aluminum on both its microstructure and hardness. It was found that aluminum not only increases the nodule count and pearlite content but also improves the hardness in both sand mold and metal mold castings. Annealing treatments were conducted to attain a homogenous microstructure and improve high-temperature serviceabil- ity. A ferrite/carbide or ferritic matrix was gained depending on the annealing temperature. It is also discovered that annealing has inverse in- fluences on the hardness of the bulk alloy and the ferrite phase. Although it causes a small decrease in the bulk hardness of the specimens, it leads to an increase in the microhardness of the ferrite. Micro-segregation of the alloying elements was also investigated by means of electron probe micro-analysis for the specimens with different annealing durations and the as-cast specimen as well. An optimum annealing time was proposed to result in the least amount of micro-segregation of aluminum and silicon between graphite nodules.
基金funded by the research scholarship ofthe Ferdowsi University of Mashhad, Iran. This support isgratefully appreciated.
文摘The purpose of this study was to determine the influence of heat treatment cycle on graphite phase formation on CK 45 steel. The presence of well distributed graphite in the matrix is responsible for the good mechanical and thermal properties of this kind of alloy. Such properties include excellent wear resistance, higher resistance to thermal shock, and higher resistance to oxidation at high temperature. A number of specimens were made up of appropriate design to provide the experimental materials. The transformation phase to a free carbon microstructure during graphitization under different conditions was then examined for the most successful experimental steels. Austenitising temperature of 920℃ and the following isothermal heat treatment of 750℃ at different holding times were used. Microstructures were examined by OM （optical microscopy） and SEM （scanning electron microscopy）. Furthermore, it was found that isothermal transformation at 750℃ for different soaking times produced a typical microstructure. Also, the amount of graphite increased with increasing isothermal heat treatment time. Heat treatment leading to supersaturation of iron with carbon was described and some of the consequences of the supersaturation were presented. Finally, the formation of the thermodynamically stable state of the graphite taken from the supersaturated solid solution was discussed.
