Guangwei HAN
,
Di FENG
,
Ming YIN
,
Wujun YE and Heli LUO(Dept. of Superalloys
,
Central Iron and Steel Research Institute
,
Beijing 100081
,
China)
材料科学技术（英文）
The recrystallization behaviour of cold drawn MP159 alloy was investigated by optical and TEM examinations. It is found that the platelet ε phase in the MP alloy inhibits the recrystallization,and this effect makes the MP159 alloy with high recrystallization temperature of about 920℃.This inhibition mainly comes from the increasing of the interfacial energy, which results from the change of the coherent interfaces of (0001)hcp//(111)fcc into the incoherent interfaces when the recrystallizing grain fronts bypass the platelet ε martensite. The increasing of the interfacial energy also causes the dissolution of a few segments on the ε martensite platelets, which decreases the strength of the MP alloy
关键词:
Guangwei HAN
,
Di FENG
,
and Wujun YE (Dept.5
,
Central Iron and Steel Research Institute
,
Beijing
,
100081
,
China)(To whom correspondence should be addressed)
材料科学技术（英文）
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.
关键词:
Guangwei HAN
,
Di FENG
,
Ming YIN and Nanseng YANG(Central Iron and Steel Research Institute
,
Beijing 100081
,
China)(To whom correspondence should be addressed)
材料科学技术（英文）
By comparing the relationship of room temperature yield strength with the reduction of cold rolled MP159 alloy before and after aging at 650℃, and by means of TEM examination on the corresponding microstructures, the occurrence of fcc(α)→hcp(ε) martensitic transition in MP159 alloy during cold deformation and the variation of the platelet E phase during aging have been Studied. The results show that the platelet E phase is really formed when the cold deformation reaches a critical value, and both the amount and the width of the platelet B phase would further increase during 650℃ aging. The increases of the amount and the width of the platelet εphase result in an additional increase of yield strength. Therefore, it is concluded that the additional hardening effect of MP159 alloy after aging is not only from the precipitation of Ni3X disperse phase but also from the volume fraction increase of the platelet ε phase. Further occurrence of the martensitic transition during aging may be due to the elimination of residual compression stress within matrix induced by the fcc(α)→hcp(ε) transition during cold deformation
关键词:
Guangwei HAN
,
Di FENG
材料科学技术（英文）
Investigation has been made on the process of synthesizing SiC/Al co-continuous composite by spontaneous melt infiltration. It is found that nitrogen atmosphere is an indispensable factor for spontaneous infiltration of melt Al into SiC preform with continuous porosity. The critical temperature for spontaneous infiltration occurrence can be lowered and spontaneous infiltration rate increased by doping a small amount of Mg into the Al alloy. Adding fine SiO2 powders into the ceramic preform can play the similar role as Mg-doping by increasing wetting through the chemical reaction of 3SiO(2)+4Al=2Al(2)O(3)+3Si at the infiltration front. Infiltration rate can also be increased by Si-doping to lower the viscosity of the molten Al alloy. In addition, sufficient Si content in the molten Al is also indispensable to avoid the formation of Al4C in the synthesized composite.
关键词:
Guangwei HAN
,
Di FENG
,
Wujun YE and Heli LUO (Dept. of Superalloy
,
Central Iron and Steel Research Institute
,
Beijing 100081
,
China)
材料科学技术（英文）
A mechanical model is presented in this paper to describe the initiating and propagating of brittle cracks. Two criteria have been deduced from the model to determine the effects of such factors as local stress state, surface and grain boundary energies as well as local grain boundary orientation on the initiating and propagating of both intergranular and transgranular brittle cracks. By which the role of adding B in Ni3Al base alloys to improve their ductility,temper and hydrogen embrittlements in steels and other alloys as well as the random feature of brittle crack initiation could be explained
关键词:
Guangwei HAN
,
Di FENG and Wujun YE (Central Iron and Steel Research Institute
,
Beijing
,
100081
,
China)
材料科学技术（英文）
Investigations have been made on the effects of temperature and fine disperse phase of disordered γ on strain hardening rate of Ni3Al based alloy. The result is found that there exists a peak temperature for the strain hardening rate of Ni3Al based alloy below the peak temperature of its yield strength. Analysis shows that the appearance of the peak temperature of strain hardening rate is caused by both the decreasing of the movability of <101> superdislocations on {111}slip plane and the increasing of the dynamic recovery in Ni3Al with increasing temperature. A Ni3Al based alloy hardened by disperse phase of disordered γ has been obtained by controlling chemical composition and treating processes. The peak temperature of strain hardening rate of this alloy is increased due to the fine disperse phase of disordered γ, which causes the reductions of the movability of the superdislocations and the dynamic recovery in Ni3Al
关键词:
