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MORPHOLOGY OF MELT SPINNING SUPERSATURATED B2 NiAl

SUN Baode , CHE Xiaozhou , LIN Dongliang , ZHOU Yaohe(Department of Materials Engineering , Shanghai Jiaotong University , Shanghai 20030 , China)(Department of Materials Science , Shanghai Jiaotong University , Shanghai 200030 , China)

金属学报(英文版)

The morphology and structure of melt spinning Ni-33.6at% Al doped with B and RE were investigated.The results show that the alloy consists of L10 martensitic grains and L12 Ni3Al at the grain boundaries when it contains no B and RE.The addition of 0.11-0.31wt% B can suppress the martensitic transformation and Ni3Al separation at the boundaries,and a supersaturated B2 single phase NiAl is obtained.The addition of 0.05wt% RE can eliminate Ni3Al precipitated at the boundaries and get complete martensite,but 0.2-0.8wt% RE addition can suppress the martensitic transformation, and supersaturated B2 single phase NiAl is obtained.The formation mechanism of supersaturated B2 single phase NiAl has been analyzed.

关键词: :NiAl , null , null , null

INFLUENCE OF GRAIN BOUNDARY MORPHOLOGY ON CREEP AND FRACTURE BEHAVIOURS OF SUPERALLOYS IN SULFUR-CONTAINING ENVIRONMENT

ZHANG Yuanhu SUN Jian XIANG Yi HU Gengxiang Shanghai Jiaotong University , Shanghai , ChinaLI Tiefan Institute of Corrosion and Protection of Metals , Academia Sinica , Shenyang , China Yuanhu , Department of Materials Science and Engineering , Shanghai Jiaotong University , Shanghai , 200030

金属学报(英文版)

Studies on the high temperature creep and fracture behaviours in air or in SO_2 contaminated environment for the Fe-base superalloy GH302 with flat or zigzag grain boundaries(GB) and the Ni-base superalloy Rene 80 were carried out.Although the creep rupture properties of the GH302 with zigzag GB was remarkably superior to that of flat GB in air,the properties of both droped dramatically in 10% SO_2-air environment,the creep rupture properties of the directional solidified Rene 80 were much better than that of the conventionally cast alloy in air,and also kept the same property in SO_2 contaminated environment as in air.Owing to the interaction between creep and sulphidation,the failure mechanism relates to the formation of molten Ni-Ni-3S_2 eutectic along GB,led to the premature failure of the alloy.

关键词: superalloy , null , null , null , null

CYCLIC DEFORMATION OF FACE CENTERED CUBIC CRYSTALS AND ITS DISLOCATION INTERACTION MODEL——Ⅱ.DISLOCATION INTERACTION MODEL OF CYCLIC DEFORMATION

JIN Nengyun Shanghai Jiaotong University Jin Nengyun , Department of Materials Science , Shanghai Jiaotong University , Shanghai 200030 , China.Present address:Max-Planck-Institut für Metallforschung , Institut für Physik , 7000 Stuttgart 80 , FRG

金属学报(英文版)

A dislocation interaction model has been proposed for cyclic deformation of fcc crystals.Ac- cording to this model,cyclic stress-strain responses and saturation dislocation structures of a crystal are associated with the modes and intensities of dislocation interactions between slip systems active in the crystal; and,hence,may be predicted by the location of its tensile axis in the crystallographic triangle.This model has successfully explained the different behaviours of double-slip crystals and multi-slip behaviours of some crystals with orientations usually con- sidered as single-slip ones.

关键词: face centered cubic crystal , null , null , null , null

SLIP FEATURE AND GRAIN BOUNDARY BEHAVIOURS OF Ni_3Al ALLOYS DURING DEFORMATION

LIN Dongliang , (T.L.Lin) , CHEN Da Shanghai Jiaotong University , Shanghai , China Professor , Dept.of Materials Science , Shanghai Jiaotong University , Shanghai 200030 , China

金属学报(英文版)

The deformation behaviours of Ni_3Al alloys with various chemical compositions and subjected to different heat treatments were in situ observed under SEM. Moreover,in situ observations of slip trace were supplemented by the direct observation of dislocation arrangements under TEM.In B-doped Ni_3Al alloys it is shown that close to the grain boundary there exists a thin slip transition region,within which slip lines are reoriented or other slip systems are operated to produce a local strain accommodation and to relax the stress concentration at grain bound- aries.Boron seems to lower the stress for dislocation generation from the grain boundaries or to ease the cross-slip close to the boundaries,and also to increase the number of dislocation sources.However,B-enhenced ductility is seriously affected by stoichiometry,the addition of a tertiary alloy element and heat treatment,etc..

关键词: Ni_3Al , null , null , null , null

CYCLIC DEFORMATION OF FACE CENTERED CUBIC CRYSTALS AND ITS DISLOCATION INTERACTION MODEL——Ⅰ.CYCLIC DEFORMATION OF COPPER CRYSTALS

JIN Nengyun Shanghai Jiaotong University , Shanghai Jin Nengyun , Department of Materials Science , Shanghai Jiaotong University , Shanghai 200030 , ChinaPresent address:Max-Planck-Institut für Metallforschung-Institut für Physik , Stuttgart 80 , FRG

金属学报(英文版)

Cyclic stress-strain responses and dislocation structure of copper single crystals with various tensile axes were systematically studied and compared with each other.Experimental results reveal that the evolution of microscopic dislocation configurations in a crystal and, accordingly,its macroscopic cyclic behaviours are closely related with its orientation.Re- markable secondary slip has been observed in some crystals with orientations well inside the crystallographic triangle, which are usually considered as single-slip ones.Their cyclio behaviours and dislocation structures at saturation are similar to those of their neighbouring multi-slip crystals.These results have constructed the experimental basis for the newly pro- posed dislocation interaction model Jor cyclic deformation of fee crystals,which will be des- cribed in the second part of this article.

关键词: Copper , null , null , null , null , null , null

THEORETICAL CALCULATION OF POINT DEFECTS IN Ni_3Al

SUN Jian LIN Dongliang Shanghai Jiaotong University , Shanghai , China LIN Dongliang , professor , Department of Materials Science , Shanghai Jiaotong University , Shanghai 200030 , China

金属学报(英文版)

Equilibrium equation of point defects in Ll_2 type intermetallic compounds was established to calculate the relations of the concentration of antisite defects and vacancies and bulk composi- tion in Ni_3Al.The examination of temperature effects on the point defects cleared up the mis. understanding of the properties of the“constitutional point defects”in Ni_3Al.

关键词: intermetallic compound , null , null , null

COMPUTER SIMULATION OF GRAIN BOUNDARY STRUCTURES IN Ni_3Al

LIN Dongliang , (T.L.Lin) , CHEN Da Shanghai Jiaotong University , Shanghai , China Professor , Dept.of Materials Science , Shanghai Jiaotong University , Shanghai 200030 , China

金属学报(英文版)

The embedded atom type potentials and static relaxation method combined with steepest gra- dient computational technique have been used to simulate the grain boundary cohesive ener- gies,the distribution of electron density and stress field in the grain boundary,region,and oth- er related problems of[100],[110]and[111]symmetric tilt grain boundaries in Ni_3Al with different grain boundary geometrical index and composition.Their relations with the segrega- tion or boron,behaviors or the grain boundary,and especially the stoichiometrical effect of B induced ductility have also been studied and discussed.

关键词: Ni_3Al , null , null , null

CREEP CRACK PROPAGATION IN CONVENTIONAL CAST AND DIRECTIONALLY SOLIDIFIED SUPERALLOY RENE 80

SUN Jian ZHANG Yuanhu HU Gengxiang Shanghai Jiaotong University , Shanghai , China SUN Jian , lecturer , Department of Materials Science , Shanghai Jiaotong University , Shanghai 200030 , China

金属学报(英文版)

The creep crack propagation in superalloy René80 of two different microstructures,i.e., equiaxed grain structure by conventional casting and columnar grain by directional solidification,was investigated under static load at 1123 K.The creep crack growth rate, da/dt,seems to be correlated with the stress intensity factor,K.The creep crack growth rate in the directionally solidified alloy is lower than that in the conventional cast alloy,owing to the elimination of transverse grain boundaries.The effect of microstructure on creep crack propagation has also been discussed.

关键词: Superalloy René 80 , null , null , null

EFFECT OF REINFORCEMENT VOLUME FRACTION ON PRECIPITATION IN MATRIX OF SiC_p/AI COMPOSITE

LIN Junshan , LI Pengxing , WU Renjie Shanghai Jiao Tong University , Shanghai , China postdoctoral , Institute of Composite Materials , Shanghai Jiaotong University , Shanghai 200030 , China

金属学报(英文版)

The differential scanning calorimetric(DSC) and transmission electron microanalysis (TEM) techniques were used to study the kinetic process of precipitation in matrix of cast SiC_p/2024 composites.The results showed that precipitation reactions of GP zone and intermediate phase S'(Al_2CuMg)in the composites were accelerated compared with SiC-free material,the peak temperatures of both reactions were decreased.The reaction enthalpies of both the GP zone and intermediate phase S' formation in the matrix were substantially decreased after the addition of SiC.TEM analysis found that the alloying element Mg segregated at the SiC/Al interfaces,and was depleted in the matrix near the interface.The precipitation-free zones(PFZ) and precipitation-sparse zones(PSZ) formed near the interfaces,as a results,the volume fraction of precipitates in matrix was reduced.

关键词: SiC_p/2024 composite , null , null

INFLUENCE OF AUSTENITE STRENGTHENING ON MARTENSITIC TRANSFORMATION IN Fe-Mn-C ALLOYS

PAN Mu XU Zuyao (T.Y.Hsu) Shanghai Jiaotong University , Shanghai , China XU Zuy(T.Y.Hsu) , Professor , Dept.of Materials Science , Shanghai Jiaotong University , Huashan Road , Shanghai 200030 , China

金属学报(英文版)

The M_s temperature and the yield strength of austenite at M_s temperature have been meas- ured for five Fe-Mn-C alloys.The experimental results show that there is a linear relation- ship between them.The effect of the solution strengthening of austenite on martensite morphology is also studied.It is pointed out that there is a characteristic temperature T_c in austenite strengthening.Martensite morphology is mainly of dislocated laths when M_s>T_c, and is mainly of twinned plates when M_s

关键词: Fe-Mn-C alloy , null , null

材料期刊网

MORPHOLOGY OF MELT SPINNING SUPERSATURATED B2 NiAl

INFLUENCE OF GRAIN BOUNDARY MORPHOLOGY ON CREEP AND FRACTURE BEHAVIOURS OF SUPERALLOYS IN SULFUR-CONTAINING ENVIRONMENT

CYCLIC DEFORMATION OF FACE CENTERED CUBIC CRYSTALS AND ITS DISLOCATION INTERACTION MODEL——Ⅱ.DISLOCATION INTERACTION MODEL OF CYCLIC DEFORMATION

SLIP FEATURE AND GRAIN BOUNDARY BEHAVIOURS OF Ni_3Al ALLOYS DURING DEFORMATION

CYCLIC DEFORMATION OF FACE CENTERED CUBIC CRYSTALS AND ITS DISLOCATION INTERACTION MODEL——Ⅰ.CYCLIC DEFORMATION OF COPPER CRYSTALS

THEORETICAL CALCULATION OF POINT DEFECTS IN Ni_3Al

COMPUTER SIMULATION OF GRAIN BOUNDARY STRUCTURES IN Ni_3Al

CREEP CRACK PROPAGATION IN CONVENTIONAL CAST AND DIRECTIONALLY SOLIDIFIED SUPERALLOY RENE 80

EFFECT OF REINFORCEMENT VOLUME FRACTION ON PRECIPITATION IN MATRIX OF SiC_p/AI COMPOSITE

INFLUENCE OF AUSTENITE STRENGTHENING ON MARTENSITIC TRANSFORMATION IN Fe-Mn-C ALLOYS

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