The antimony segregation at grain boundary was observed and the temper embrittlement in titanium-doped nickel-chromium steel was analyzed. It is concluded that the antimony segregation at grain boundary is nonequilibi...The antimony segregation at grain boundary was observed and the temper embrittlement in titanium-doped nickel-chromium steel was analyzed. It is concluded that the antimony segregation at grain boundary is nonequilibium and the kinetics of temper embrittlement agrees well with those of nonequilibrium antimony segregation at grain boundary. Besides, the mechanism of nonequilibrium antimony segregation at grain boundary proved to be the most satisfactory one among the existing mechanisms to interpret the antimony induced embrittlement kinetics in the nick- el-chromiunl steel. Based on these, the activation energy and frequency factor of diffusion of antimony vacancy complexes were obtained according to the concept of critical time in nonequilibrium grain boundary segregation theory.展开更多
The data obtained by bending tests for intergranular embrittlement after 45 h and 450 h exposure to Strauss solution have been reported for 304 stainless steel. The results show that an embrittlement peak appears at ...The data obtained by bending tests for intergranular embrittlement after 45 h and 450 h exposure to Strauss solution have been reported for 304 stainless steel. The results show that an embrittlement peak appears at 650℃ for all samples quenched from 1260℃ and then sensitized for 150 h at 480, 565, 650, 730, 815 and 900℃ respectively. The temperature corresponding to the embrittlement peak is decreased to 565℃ when the sensitizing time is prolonged to 1 500 h. In this paper, these data are analyzed with an isothermal kinetic model of nonequilibrium grain boundary segregation, indicating that the embrittlement peak is related to the critical time for nonequilibrium grain boundary segregation of sulfur.展开更多
The effect of phosphorus content and heat treatment on the segregation of phosphorus and precipita- tion of phosphide at the grain boundary of IN706 alloy has been investigated, The phosphide had a stoichiometry of M...The effect of phosphorus content and heat treatment on the segregation of phosphorus and precipita- tion of phosphide at the grain boundary of IN706 alloy has been investigated, The phosphide had a stoichiometry of MNP （M = Nb, Ti and N = Ni, Fe, Cr） and an orthorhombic crystal structure. The solubil- ity of phosphorus in the grain matrix of IN706 alloy was determined to be between 0.008% and 0.013%. When soaked at 980 ℃ for 5 min, the phosphide was noticeably precipitated at grain boundaries with the grain size unchanged. When soaked at 980 ℃ for 3 h, the grains grew significantly, but the phos- phide stayed at original grain boundaries which outlined the grain shape before soaking. Soaking at 1060 ℃ for 2 h fully dissolved the pre-existing phosphide but phosphorus atoms were not distributed uni- formly in the grain matrix. When the holding time at 1060 ℃ was extended to 10 h, the phosphorus atoms were distributed uniformly in the grain matrix by sufficient diffusion, and the phosphide could only be formed at grain boundaries during the 980 ℃ soaking. The precipitation of phosphide mainly relied on the phosphorus segregation which was built up by diffusion.展开更多
The influence of tin on the hot ductility of a 0.15wt%C steel is investigated using a continuous-casting thermal simulator with three cooling rates. Tin can apparently deteriorate the hot ductility of the steel. Non-e...The influence of tin on the hot ductility of a 0.15wt%C steel is investigated using a continuous-casting thermal simulator with three cooling rates. Tin can apparently deteriorate the hot ductility of the steel. Non-equilibrium grain boundary segregation of tin occurs during cooling and plays an important role in reducing the hot ductility of the steel. There is a critical cooling rate for the Sn segregation being between 5 and 20K/s.展开更多
基金Item Sponsored by National Natural Science Foundation of China(51001011)
文摘The antimony segregation at grain boundary was observed and the temper embrittlement in titanium-doped nickel-chromium steel was analyzed. It is concluded that the antimony segregation at grain boundary is nonequilibium and the kinetics of temper embrittlement agrees well with those of nonequilibrium antimony segregation at grain boundary. Besides, the mechanism of nonequilibrium antimony segregation at grain boundary proved to be the most satisfactory one among the existing mechanisms to interpret the antimony induced embrittlement kinetics in the nick- el-chromiunl steel. Based on these, the activation energy and frequency factor of diffusion of antimony vacancy complexes were obtained according to the concept of critical time in nonequilibrium grain boundary segregation theory.
基金Item Sponsored by National Natural Science Foundation of China(50771036,51001030)
文摘The data obtained by bending tests for intergranular embrittlement after 45 h and 450 h exposure to Strauss solution have been reported for 304 stainless steel. The results show that an embrittlement peak appears at 650℃ for all samples quenched from 1260℃ and then sensitized for 150 h at 480, 565, 650, 730, 815 and 900℃ respectively. The temperature corresponding to the embrittlement peak is decreased to 565℃ when the sensitizing time is prolonged to 1 500 h. In this paper, these data are analyzed with an isothermal kinetic model of nonequilibrium grain boundary segregation, indicating that the embrittlement peak is related to the critical time for nonequilibrium grain boundary segregation of sulfur.
文摘The effect of phosphorus content and heat treatment on the segregation of phosphorus and precipita- tion of phosphide at the grain boundary of IN706 alloy has been investigated, The phosphide had a stoichiometry of MNP （M = Nb, Ti and N = Ni, Fe, Cr） and an orthorhombic crystal structure. The solubil- ity of phosphorus in the grain matrix of IN706 alloy was determined to be between 0.008% and 0.013%. When soaked at 980 ℃ for 5 min, the phosphide was noticeably precipitated at grain boundaries with the grain size unchanged. When soaked at 980 ℃ for 3 h, the grains grew significantly, but the phos- phide stayed at original grain boundaries which outlined the grain shape before soaking. Soaking at 1060 ℃ for 2 h fully dissolved the pre-existing phosphide but phosphorus atoms were not distributed uni- formly in the grain matrix. When the holding time at 1060 ℃ was extended to 10 h, the phosphorus atoms were distributed uniformly in the grain matrix by sufficient diffusion, and the phosphide could only be formed at grain boundaries during the 980 ℃ soaking. The precipitation of phosphide mainly relied on the phosphorus segregation which was built up by diffusion.
基金supported by the Natural Science Foundation oy Hubei Province(NO.2000J018).
文摘The influence of tin on the hot ductility of a 0.15wt%C steel is investigated using a continuous-casting thermal simulator with three cooling rates. Tin can apparently deteriorate the hot ductility of the steel. Non-equilibrium grain boundary segregation of tin occurs during cooling and plays an important role in reducing the hot ductility of the steel. There is a critical cooling rate for the Sn segregation being between 5 and 20K/s.
