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EFFECT OF MAGNETIC FIELD ON MARTENSITIC TRANSFORMATION IN Fe-21Ni-4Mn ALLOY

SUN Enxi Dalian Railway College , Dalian , ChinaYANG Dazhi Dalian University of Technology , Dalian , ChinaXU Zuyao (T.Y.Hsu) Shanghai Jiaotong University , Shanghai , ChinaYANG Fuming ZHAO Ruwen Institute of Physics , Academia Sinica , Beijing , China YANG Dazhi , Professor , Dalian University of Technology , Dalian 116024 , China

金属学报(英文版)

The pulsed magnetic field induced martensitic transformation with isothermal and athermal kinetics in Fe-2Ni-4Mn(wt-%)alloy has been studied by means of magnetization measurements,optical microscopy and thermodymical analyses.It is shown that there exits a critical magnetic intensity for induing martensitic transformation at a given temperature above Ms.The critical magnetic field increases linearly with increasing ΔT= T-M_S.The magnetic field strongly promotes the athermal martensitic transforamtion and restrains the isothermal one.The entropy change ΔS for athermal transformation at Ms is 4.13 J/mol· K.The effect of magnetic field on martensitic transformation in Fe-21Ni-4Mn alloy is main- ly due to Zeeman effect.Lath,plate and butterfly martensities were observed under magnetic field.

关键词: magnetic field-induced martensitic transformation , null , null

Isothermal Aging Kinetics in CuZnAl Shape Memory Alloy

Zengqi ZHAO Lab.of Physics , Baotou Research Institute of Rare Earth , Baotou , 014010 , ChinaFeixia CHEN Dazhi YANG Dept.of Mater.Eng. , Dalian University of Technology , Dalian , 116024 , ChinaEr BAO Dept.of Mater.Eng. , Yanshan University , Qinhuangdao , 066004 , China

材料科学技术(英)

Isothermal aging behaviours of a CuZnAl shape memory alloy have been investigated by means of dilatometry.The length of the specimens during isothermal aging from 190 to 280℃ increases with the aging time at each temperature.The isothermal aging kinetics fits in Avrami equation and the time exponent n decreases with the increase in aging temperature.The apparent activation energy for the isothermal aging process was measured to be 109.0kJ/mol,which is about equal to that of a relaxation internal friction peak at about 200℃ (f≈1 Hz) in the alloy.

关键词: isothermal aging kinetics , null , null , null , null

EFFECT OF NITROGEN ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ALLOY HK50

YU Yongsi CAO Zhiben WANG Fugang , Dalian University of Technology , Dalian , ChinaGUO Xiaobing Jinzhou Institute of Technology , Jinzhou , China Associate Professor , Dept.of Materials Science , Dalian University of Technology , Dalian 116024 , China

金属学报(英文版)

The volume fraction of the lamellar carbide cell in HK50 alloy may be increased with the in- crease of nitrogen content over 0.065%.The habit plane of l(?)mellar carbide is {111}_γ.The distribution of nitrogen changes no more before or after the precipitation of lamellar structure. The diffusion activation energy of carbon reduces remarkably with the increase of nitrogen content.It is believed that the lamellar carbide cell is harmful to the high temperature creep and impact properties of the alloy.

关键词: alloy HK50 , null , null , null

(α+β)Dual Phase CuZnAl Shape Memory Alloy

ZHAO Xu , QI Min , YANG Dazhi Institute of Metal Research , Academia Sinica , Shenyang , 110015 , China.Department of Materials Engineering , Dalian University of Technology , Dalian , 116012 , China.

材料科学技术(英)

The effect of α phase on CuZnAl shape memo- ry alloy(SMA)has been systematically studied by electrical resistance method,quantitative measure- ment of micrography and transmission electron microscopy(TEM).It is found that,by controlling the amount of α phase in(α+β)-CuZnAl alloy, phase transformation temperatures can be adjusted precisely in a wide range,while the good shape memory effect of CuZnAl is kept.In a word, quenching from(α+β)dual phase region is a rea- sonable method of adjusting phase transformation temperatures for CuZnAl alloy.

关键词: (α+β)-CuZnAl alloy , null , null

Relationship between Relaxation Internal Friction Peak at about 200℃(f≈1Hz)and Bainitic Transformation In a CuZnAl Alloy

ZHAO Zengqi CHEN Feixia YANG Dazhi BAO Er ** Physical Laboratory , Baotou Research Institute of Rare Earth , Baotou , 014010 , China*** Dept.of Materials Engineering , Dalian University of Technology , Dalian , 116024 , China**** Dept.of Materials Engineering , Yanshan Uni

材料科学技术(英)

The present investigation showed that the re- laxation peak at about 200℃ (f≈1Hz) was related to bainitic transformation in a CuZnAl alloy.The peak decreased when bainite precipitated.The activation energy of the peak was the same as the apparent activation energy of bainitic transforma- tion.According to the relations between the peak and the bainitic transformation,the mechanism of the peak has been discussed.

关键词: internal friction , null , null , null

Influence of α Phase on Shape Memory Effect and Superelasticity of CuZnAI Alloy

QI Min ZHU Min ZHAO Xu YANG Dazhi ** Dept.of Materials Engineering , Dalian University of Technology , Dalian , 116023 , China*** Institute of Metals Research , Academia Sinica , Shenyang , 110015 , China+ To whom correspondence should be addressed

材料科学技术(英)

The influence of a small amount of α phase in β′ matrix on shape memory effect and superelasticity of CuZnAl shape memory alloy has been studied systematically.It has been found that transformation temperature can be adjusted in a large scale by controlling the amount of α phase, meanwhile,shape memory effect and superelasticity do not decrease obviously when there exists a small amount of α phase.Based on the optical and trans- mission electron microscopy observation,the influ- ence of α phase on shape memory effect and superelasticity has been discussed.

关键词: αphase , null , null , null

GRAIN BOUNDARY FEATURE AND CREEP BEHAVIOR OF Fe-15Cr-25Ni ALLOYS

ZHANG Junshan CHEN Weixing CAO Zhiben Dalian University of Technology , Dalian , China Associate Professor , Department of Materials Engineering , Dalian University of Technology , Dalian , China

金属学报(英文版)

Creep behavior of Fe-15Cr-25Ni alloys with different grain boundary features has been in- vestigated at 850 and 950℃ and in stress range of 14.7~78.5 MPa.The single phase alloy exhibits typical recovery creep characteristics,and for the alloy in which M_(23)C_6 carbides densely precipitate at grain boundaries,the creep rate dramatically decreases and creep behav- ior is also significantly different from the single phase alloy.When the carbides precipitate at grain boundaries,the dislocation density are higher and the size of subgrains near grain boundaries are smaller than those of single phase alloy.The creep mechanisms for two grain boundary features have been discussed.

关键词: grain boundary feature , null , null

A QUENCHING INDUCED PLANAR DEFECT OF MARTENSITE IN Cu-Zn-Al ALLOY

ZHU Min YANG Dazhi Dalian University of Technology , Dalian , China Lecturer , Dept.of Matedais Engineering , Dalian University of Technology , Dalian , China

金属学报(英文版)

A new kind of planar defect named non-basal plane stacking faults has been studied by using trace analysis and lattice image techniques.It has been found that they are located in (125)_M plane of martensite lattice.By lattice image observation,the non-basal plane stack- ing faults are argued to be induced by two incomplete basal plane stacking faults and may be the results of rapid quenching.The defects are regarded as anomalous structures of martensite.

关键词: martensite , null , null

INFLUENCE OF RARE EARTH ON INTERGRANULAR CRACKING OF 9% Ni CAST STEEL

ZHANG Wei LI Longsheng CHENG Ji Dalian University of Technology , Dalian , China Lecturer , Dept.of Materials Engineering , Dalian University of Technology , Dalian 116023 , China

金属学报(英文版)

The intergranular cracking of 9% Ni cast steel seems mainly to relate to the segregation of contaminates H,S and P along boundaries.An addition of rare earth may eliminate the seg- regation of these contaminates along grain boundaries and improve the binding force among boundaries,so as to reduce remarkably the intergranular cracking.

关键词: 9%Ni cast steel , null , null

Diffraction and Morphology Study of Surface Structures Accomponying with the Formation of α'Plate(Bainite)in a Cu-Zn-AI Alloy

ZHU Min AN Jiangying CHEN Feixia WANG Fengting YANG Dazhi ** Dept.of Materials Engineering , Dalian University of Technology , Dalian , 116023 , China+ To whom correspondence should be addressed

材料科学技术(英)

In the present paper the morphologies of sur- face structures and the anomalous contrast of β_1 phase accompanying with the formation of bainite plate in the Cu-Zn-Al shape memory alloy have been investigated in detail by the transmission elec- tron microscopy and diffraction.The experimental results have proved that the extra diffraction and anomalous contrast results from the surface martensite formed on the β_1 phase.However,the crystal structure and morphology of the surface martensite are varied at different stage of bainite formation.The observation of interfacial disloca- tion structure of bainite/β_1 matrix reveals that there is a large strain in the bainite transformation of β CuZnAl alloy.Based on the experiment results the formation of surface martensite and bainitic transformation were discussed.

关键词: shape memory alloy , null , null

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