Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stre...Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.展开更多
The kinetics of the surface reactions of single crystal Ni3Al and polycrystal line Ni3Al0.00052 wt% B with water vapor or oxygen was investigated using XPS. Both reactions initiate at less than 1.5×10-6 Pa.s expo...The kinetics of the surface reactions of single crystal Ni3Al and polycrystal line Ni3Al0.00052 wt% B with water vapor or oxygen was investigated using XPS. Both reactions initiate at less than 1.5×10-6 Pa.s exposure. The reaction of Ni3Al does not saturote with water vapor at 0.43 Pa.s; with oxygen at 8.4×10-2 Pa.s and the oxide formed is Al2O3. The kinetics of these reactions can be used to eaplain the different ductility behavior of Ni3Al-based alloys in various environment.展开更多
Research work and recent progress made toward the industrial applications of the Ni_3Al in CISRI are discussed in present paper. The development of a Ni_3Al base alloy named MX-246 hardened by carbides and fine disper...Research work and recent progress made toward the industrial applications of the Ni_3Al in CISRI are discussed in present paper. The development of a Ni_3Al base alloy named MX-246 hardened by carbides and fine dispersion of disordered γ is summaried. This alloy,with higher peak temperature of yield strength and higher strain hardening rate than alloyIC-218,has been successfully used as the material of rolling guider at elevated temperatures and in wear conditions. The Ni3Al base alloy of GH264 has been made into welding electrodes by horizontal continuous casting process, and recently successfully surfacing welded on hydraulic blades as cavitation erosion resistance material. The process of remelting Ni3Al base alloy in air was also developed. The processes of producing welding electrodes and remelting in air set the base of industrial applications of Ni3Al in welding, repairing and casting in mass production and into components of large size. Another application of the compound, manufacturing the jet engine rivets used at about 1300℃ , can be attributed to its excellent oxidation resistance and still keeping high strength up to the melting point.展开更多
The recrystallization behavior of Ni 3 Al base single crystal alloy IC6SX with different mechanical processes has been studied.The specimens of the alloy were treated by surface cleaning and cold working during the bl...The recrystallization behavior of Ni 3 Al base single crystal alloy IC6SX with different mechanical processes has been studied.The specimens of the alloy were treated by surface cleaning and cold working during the blades manufacture,and then heat treated in the temperature range of 800-1260℃ for 1 h to 4 h.The microstrcture of the specimens were examined by optical and scaning electron microscopy,and the room temperature tensile property,stress rupture property under the test condition of 1100℃/130 MPa,and the thermal cycle fatigue resistance under 1100-20℃ of the specimens with and without recrystallization were carried out.The experimental results showed that the initial recrystallization nucleation temperatures of the alloy by dry grit blasting,wet grit blasting,indentation,shot blasting and burnishing were 900-950℃/1 h,1000-1100℃/1 h,1200-1220℃/4 h,1220-1240℃/1 h and 1220-1240 C/1 h,respectively and the primal recrystallization completing temperatures of the alloy by those mechanical processes mentioned above were 1200-1210℃/1 h,1100-1200℃/1 h,1220-1240℃/4 h,1240-1260℃/1 h and 1240-1260℃/1 h,respectively.The results also indicated that the deformation amount of the specimens by burnishing and dry grit blasting was bigger than that by wet grit blasting and shot blasting according to their recrystallization temperature and the microhardness profile below the surface of specimens.It has been found that the recrystallization had no evident effect on mechanical properties of the alloy.展开更多
Potassium （K） and nitrogen （N） are essential nutrients for plants. Adsorption and desorption in soils affect K＋ and NH4＋ avail- abilities to plants and can be affected by the interaction between the electrical d...Potassium （K） and nitrogen （N） are essential nutrients for plants. Adsorption and desorption in soils affect K＋ and NH4＋ avail- abilities to plants and can be affected by the interaction between the electrical double layers on oppositely charged particles because the interaction can decrease the surface charge density of the particles by neutralization of positive and negative charges. We studied the effect of iron （Fe）/aluminum （Al） hydroxides on desorption of K＋ and NH4＋ from soils and kaolinite and proposed desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and the positively charged Fe/Al hydroxide particles. Our results indicated that the overlapping of diffuse layers of electricM double layers between positively charged Fe/Al hydroxides, as amorphous Al（OH）3 or Fe（OH）3, and negatively charged surfaces from an Ultisol, an Alfisol, and a kaolinite standard caused the effective negative surface charge density on the soils and kaolinite to become less negative. Thus the adsorption affinity of these negatively charged surfaces for K＋ and NH4＋ declined as a result of the incorporation of the Fe/Al hydroxi- des. Consequently, the release of exchangeable K＋ and NH4＋ from the surfaces of the soils and kaolinite increased with the amount of the Fe/A1 hydroxides added. The greater the positive charge on the surfaces of Fe/Al hydroxides, the stronger was the interactive effect between the hydroxides and soils or kaolinite, and thus the more release of K＋ and NH4＋. A decrease in pH led to increased positive surface charge on the Fe/Al hydroxides and enhanced interactive effects between the hydroxides and soils/kaolinite. As a result, more K＋ and NH4＋ were desorbed from the soils and kaolinite. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of K＋ and NH4＋ in the soils and thus increase their leaching loss.展开更多
文摘Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.
文摘The kinetics of the surface reactions of single crystal Ni3Al and polycrystal line Ni3Al0.00052 wt% B with water vapor or oxygen was investigated using XPS. Both reactions initiate at less than 1.5×10-6 Pa.s exposure. The reaction of Ni3Al does not saturote with water vapor at 0.43 Pa.s; with oxygen at 8.4×10-2 Pa.s and the oxide formed is Al2O3. The kinetics of these reactions can be used to eaplain the different ductility behavior of Ni3Al-based alloys in various environment.
文摘Research work and recent progress made toward the industrial applications of the Ni_3Al in CISRI are discussed in present paper. The development of a Ni_3Al base alloy named MX-246 hardened by carbides and fine dispersion of disordered γ is summaried. This alloy,with higher peak temperature of yield strength and higher strain hardening rate than alloyIC-218,has been successfully used as the material of rolling guider at elevated temperatures and in wear conditions. The Ni3Al base alloy of GH264 has been made into welding electrodes by horizontal continuous casting process, and recently successfully surfacing welded on hydraulic blades as cavitation erosion resistance material. The process of remelting Ni3Al base alloy in air was also developed. The processes of producing welding electrodes and remelting in air set the base of industrial applications of Ni3Al in welding, repairing and casting in mass production and into components of large size. Another application of the compound, manufacturing the jet engine rivets used at about 1300℃ , can be attributed to its excellent oxidation resistance and still keeping high strength up to the melting point.
文摘The recrystallization behavior of Ni 3 Al base single crystal alloy IC6SX with different mechanical processes has been studied.The specimens of the alloy were treated by surface cleaning and cold working during the blades manufacture,and then heat treated in the temperature range of 800-1260℃ for 1 h to 4 h.The microstrcture of the specimens were examined by optical and scaning electron microscopy,and the room temperature tensile property,stress rupture property under the test condition of 1100℃/130 MPa,and the thermal cycle fatigue resistance under 1100-20℃ of the specimens with and without recrystallization were carried out.The experimental results showed that the initial recrystallization nucleation temperatures of the alloy by dry grit blasting,wet grit blasting,indentation,shot blasting and burnishing were 900-950℃/1 h,1000-1100℃/1 h,1200-1220℃/4 h,1220-1240℃/1 h and 1220-1240 C/1 h,respectively and the primal recrystallization completing temperatures of the alloy by those mechanical processes mentioned above were 1200-1210℃/1 h,1100-1200℃/1 h,1220-1240℃/4 h,1240-1260℃/1 h and 1240-1260℃/1 h,respectively.The results also indicated that the deformation amount of the specimens by burnishing and dry grit blasting was bigger than that by wet grit blasting and shot blasting according to their recrystallization temperature and the microhardness profile below the surface of specimens.It has been found that the recrystallization had no evident effect on mechanical properties of the alloy.
基金Supported by the Knowledge Innovation Program Foundation of the Chinese Academy of Sciences (No. KZCX2-EW-405)the National Natural Science Foundation of China (Nos. 40971135 and 40901110)
文摘Potassium （K） and nitrogen （N） are essential nutrients for plants. Adsorption and desorption in soils affect K＋ and NH4＋ avail- abilities to plants and can be affected by the interaction between the electrical double layers on oppositely charged particles because the interaction can decrease the surface charge density of the particles by neutralization of positive and negative charges. We studied the effect of iron （Fe）/aluminum （Al） hydroxides on desorption of K＋ and NH4＋ from soils and kaolinite and proposed desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and the positively charged Fe/Al hydroxide particles. Our results indicated that the overlapping of diffuse layers of electricM double layers between positively charged Fe/Al hydroxides, as amorphous Al（OH）3 or Fe（OH）3, and negatively charged surfaces from an Ultisol, an Alfisol, and a kaolinite standard caused the effective negative surface charge density on the soils and kaolinite to become less negative. Thus the adsorption affinity of these negatively charged surfaces for K＋ and NH4＋ declined as a result of the incorporation of the Fe/Al hydroxi- des. Consequently, the release of exchangeable K＋ and NH4＋ from the surfaces of the soils and kaolinite increased with the amount of the Fe/A1 hydroxides added. The greater the positive charge on the surfaces of Fe/Al hydroxides, the stronger was the interactive effect between the hydroxides and soils or kaolinite, and thus the more release of K＋ and NH4＋. A decrease in pH led to increased positive surface charge on the Fe/Al hydroxides and enhanced interactive effects between the hydroxides and soils/kaolinite. As a result, more K＋ and NH4＋ were desorbed from the soils and kaolinite. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of K＋ and NH4＋ in the soils and thus increase their leaching loss.
