Z.F. Peng
,
Y Y Ren
,
B.Z. Fan
,
J. W Qin
,
P. Yan
,
J. C. Zhao
,
Y Q. Wang and J.H. Sun (Wuhan University of Hydraulic and Electric Engineering
,
Wuhan 430072
,
China)(Central Iron and Steel Research Institute
,
Beijing 100081
,
China)
金属学报(英文版)
Prolonged tension tcsts were caTried out by comblning elevated temperatures with declined stresses over thc range of 760-1050° C and 780-115MPa. The effects of temperature and applied stress on rupture life, and the relations of temperuture, applied stress and mpture life to characteristic dimensions of coherent phases (γ matrix channel width and mpcd γ precipitate thickness), and to the elongation as well as to the cross sectional area reduction of thc tested specimens were investigated. Under all testing conditions, longittLdinal coalescence of seveml adjacent armys of γ precipitates could occur to dtherent extents along the direction of the applied stress axis in addition to their normal directional coarsening. The extent of γ Longitudinal coalescence became increased and its morphology tended to be irmpular with the increase of temperuture although the applied stresses were relatively lower.
关键词:
superalloy CMSX-2
,
null
,
null
,
null
J.M. Zhang
,
L.Z. Ma
,
J. Y. Zhuang
,
Q. Deng
,
J.H Du and Z. Y Zhong(Department of Superalloys
,
Central Iron & Steel Research Institute
,
Beijing 100081
,
China)P. Janschek(Thyssen Umformtechnik GMBH
,
42859 Remscheid
,
Germany Manuscript received 26 August 1996)
金属学报(英文版)
Isothermal constant speed compression tests of superalloy IN718 were conducted using a computer-controlled MTS machine at temperatures from 960 to 1040℃, with initial strain rates from 0.001 s~(1) to 1.0 s~(1) and engineering strain from 0.1 to 0. 7.The variations of flow stress with deformation temperature, initial strain rate and engineering strain were analyzed in the paper. It was found that there was an obvious power-law relationship between flow stress and initial strain rate, which showed the behavior of strain rate hardening of superalloy IN718 at elevated temperatures.The relationship between flow stress and temperature could be described by an inverse trigonometric function.And the turning point on the curve may be related to the behavior of δ phase at 1000℃. Meanwhile, it was found that there was a complicated relationship between flow stress and strain,which was indicative of the comprehensive effect of work hardening and dynamic softening on flow stress during hot deformation. From the results of these tests, a constitutive equation of superalloy IN718 was developed.
关键词:
: constitutive relationship
,
null
,
null
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）
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
,
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）
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
,
Wujun YE and Heli LUO (Dept. of Superalloy
,
Central Iron and Steel Research Institute
,
Beijing 100081
,
China)
材料科学技术（英）
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:
H. R. Hou
,
Q. Y. Liu
,
Q. A. Chen and H. Dong Division of Structural Materials
,
Central Iron & Steel Research Institute
,
Beijing 100081
,
China
金属学报(英文版)
Heavy deformation and controlled cooling is one of the most effective effective ways for grain refinement in HSIA steels. In this paper, experimental specimens are prepared with a commercial linepipe steel grade X65, and the chemical compositions are (wt% ): Fe-0.094C-1.42Mn-0. 29Si-0. 045Nb-0. 008Ti. After heavy deformation with 80% reduction in non-recrystallization range of austenite, and at controlled cooling rates from 2K/s to 64K/s, the grain sizes vary from 9.55μm to 1.06μm.It is shown by the results that a linear relationship still remains between the yield strength and reciprocal of square root of ferrite grain size as grain size is refined to 1m.The ultra-fine grains might be dynam- ically formed through the deformation-induced transformation when reduction is large enough.The grain sizes decrease when the cooling rates increase.When the cooling rates increase over 10K/s, the grain sizes are rarely changed. The particles distribute on grain boundaries, sub-grain boundaries, deformed bands and within the ferrite grains.
关键词:
microalloyed steel
,
null
,
null
,
null
S.Q. Li
,
J.I. Dickson and J.P. Bailon (Central Iron and Steel Research Institute (CISRI)
,
Beijing 100081
,
China)(Ecole Polytecnique de Montreal
,
Montreal H3C 3A7
,
Canada)
金属学报(英文版)
The microfractography of transgranular stress corrosion cracking (TSCC) of 70Cu-30Zn a-brass in ammoniacal solution was studied. The observations indicate that on a very microscale, the crack path of TSCC of or-brass follows {111} planes. The crack path very often alternates between {111} Planes to result in "cleavage-like"facet, the usual average orientation of which is {110} with preferential microscopic crack propagation in (100) and (112) directions. The average orientation of wide secondary facets is often close to {100}. The size of {111} microfacets increases with incrmsing stress intensity K, which indicates that the microscopic crack path follows {111} planes on which some localized slip has occurred. Possible TSCC mechanisms which appear to be consistent with the microfraphic features observed in the present study are also discussed.
关键词:
fractography
,
null
,
null
,
null
