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INTERACTION OF PRECIPITATION AND RECRYSTALLIZATION IN RAPIDLY SOLIDIFIED Cu-Cr-Zr-Mg ALLOY

Liu , B.X. Kang , X.G. Cao , J.L. Huang , B. Yinand H.C. Gu (Institute of Materials Science and Engineering , Xi'an Jiaotong University , Xi'an 710049 , China)(Institute of Materials Science and Engineering , Xi'an Jiaotong University , Xi'an 710049 , China)( Department of Materials Engineering , Luoyang Institute of Technology , Luoyang 471049 , China)( Department of Materials Engineering , Luoyang Institute of Technology , Luoyang 471049 , China)( Department of Materials Engineering , Luoyang Institute of Technology , Luoyang 471049 , China)( Department of Materials Engineering , Luoyang Institute of Technology , Luoyang 471049 , China)

金属学报(英文版)

In this paper; the recrystallization process during aging for a rapidly solidified Cu-Cr-Zr-Mg alloy has been investigated. It is found that the discotinuous crystallization process has been partially retarded by the ultra-fine and dispersed precipitation upon aging after deformation. Thus, a phenomenon of combined in situ and discontinuous recrystallization has been observed in the rapidly solidified Cu-Cr-Zr-Mg alloy.On the nucleation and growth of recrystallization, the precipitated phases are coarscned and dissolved in the front of grain boundaries following a re-precipitation in the recrystallization area,which results in the much more dispersed precipitates.

关键词: rapid solidification; Cu-Cr-Zr-Mg alloy; aging precipitation; recrystallization

ATOMIC SCALE MECHANISM OF RESTRAINED EMBRITTLEMENT IN AMORPHOUS Fe_(78)B_(13)Si_9 ALLOY BY ELECTRIC PULSE RAPID ANNEALING

J.L. Huang , X.G. Cao , E. Sukedai , S. Yamasaki , and H.C.Gu(Department of Materials Engineering , Luoyang Institute of Technology , Luoyang 471039 , China)(Department of Mechanical Engineering , Okayama University of Science , 1-1 Ridai-Cho , Okayama City , Okayma 700 , Japan)(Institute of Materials Science and Engineering , Xi'an Jiaotong University , Xi'an 710049 , China)

金属学报(英文版)

The direct observations of the atomic arrangements in both conventional furnace annealed and electric pulse rapid annealed Fe78B13Si9 amorphous alloy have been conducted by the lattice imaging technique in a higt resolution electron microscope. The results showed that the embrittlement of the alloy was related to the extent of atomic rearrangements during the annealing processes. The embrittlement of the alloy after 1hour conventional furnace annealing at about 270℃ is caused by the sufficient atomic rearrangements which are characterized by the growth of some bct Fe3B-like atomic short range ordering regions already existed in the as-quenched structure. Electric pulse rapid annealing can effectively retard the above-mentioned atomic rearrangements and thus restrain the embrittlement. The embrittlement only occurs when certain amount of bcc α-Fe nanocrystals are precipitated in the amorphous matrix during electric pulse rapid annealing.

关键词: Fe_(78)B_(13)Si_9 amorphous alloy , null , null , null

OUT OF PILE CORROSION RESISTANCE OF NEW ZIRCONIUM ALLOYS IN 500 ℃/10 3MPa STEAM

Z.K. Li 1 , 2) , L.Zhou 1 , 2) , J.Z. Liu 1) , P.Z. Li 1) and W.J. Zhao 3) 1) Northwest Institute for Nonferrous Metal Research , Xi'an 710016 , China 2) Xi'an Jiaotong University , Xi'an 710049 , China 3) Nuclear Power Institute of China , Chengdu 610041 , China M

金属学报(英文版)

he out of pile corrosion resistance of new Zirconium alloys in 500℃/10 3MPa steam has been investigated and the effect of alloying elements, Sn,Nb,Fe,Cr on the property has been analyzed. The results show that the new alloys have better corrosion resistance than Zircaloy 4. That no nodular corrosion is found during test cycles shows the nodular corrosion resistance can be dramatically improved by addition of alloying elements Nb. The Fe/Cr ratio should be properly controlled if there is Cr addition in the alloys when developing new alloys.

关键词: zirconium alloy , null , null , null

EFFECT OF SILICON ON PRODUCING DUCTILE IRON WITH COMPLEX STRUCTURE OF BAINITE AND MARTENSITE

Y. P. Zhang , J.X. Zhu , Y. Q. Wang and J.Y.Su(Institute of Cast Iron Research , Xi'an University of Technology , Xi'an 710048 , China)(Department of Mechanical Engineering , Xi'an Jiaotong University , Xi'an 710049 , China)

金属学报(英文版)

This paper deals with an important role of silicon in producing ductile iron with quenched complex structure of bainite and martensite. The samples are cast in permanent mold and quenched in solution of sodium silicate. The result of thc experiments shows that the austenizing temperature should rise with increasing silicon content, otherwise much undissolved ferrite is present in the matrix after quenching. However the undissolvec ferrite can be decreased greatly or even eliminated by adding appropriate amount of ooron. On this condition, the amount of bainite gets increasing and the amount of residual austenite decreasing with the silicon cortent increasing. An approach has also been made to the mechanism of the effect of silicon on the transformation of bainite in ductile iron. The T.T.T. curves measured show that the increase of sllicon content causes the curve to shift to the left. This is quite different from the fact in steel.

关键词: ductile iron , null , null , null

EXPERIMENTAL INVESTIGATION ON HISTORY-DEPENDENCE OF PLASTIC BEHAVIOR OF TYPE 302 STAINLESS STEEL UNDER COMBINED AXIAL-TORSIONAL LOADS

S.X. Zhao , X.F. Sun and Z.B. Kuang (Institute of Applied Mechanics , Southwestern Jiaotong University , Chengdu 610031 , China)(Institute of Engineering Mechanics , Xi'an Jiaotong University , Xi'an 710049 , China)

金属学报(英文版)

Experimental investigations were pedermed on the plastic deformation along bilinear strain paths with various values of corner-angle by subjecting thin-walled tubular specimens of type 302 stainless steel to combined axial and torsional loads. Variations of scalar and vectorial behavior of the stress response are discnssed in the vector space of plastic strain. It is found that the intrinsic geometry of loading path, the plastic strain history and the coapled effect among strain components effect effectively the stress response of the material. The experimental results also show that these effects will disappear gradually with increasing strain.

关键词: complex loading , null , null

STUDY OF THE MICROSTRUCTURE SIMULATION AND PERFORMANCE OF FUSION WELDING HAZ OF ZINC-BASED ALLOY

K.K. Zhang , D.R. Chen , J. Xue , D. W. Sun and H.C. Li( 1) Department of Materials Engineer , Xi'an Jiaotong University , Xi'an 710049 , China 2) Luoyang Institute of Technology , Luoyang 471039 , China 3) CITIC Heavy)

金属学报(英文版)

Base on a vast amount of testing and calculations for the welding thermal cycling curves of different testing points in fusion welding (TIG welding, gas welding) HAZ of zinc-based alloy with low melting points, this paper defines the welding thermal cycle parameters of microstructure stimulation of HAZ by zinc-based alloy fusion welding process. On the principle of which the microstrnct,are and harkness of the testing points in simulation specimens are basically correspondence with that of actual welding HAZ, the microstructure simulation of testing points Tm=370O℃. 305℃) of ZA12 alloy by fusion welding is carried out by the means of omhic-heating welding thermal simulation tester. The study results of the abrasion-resistance of simulation specimens HAZ by fusion welding process indicates that the abmsion-resistance is closely related to the form of eutectoid microstructure in or in the structure.

关键词: zinc-based alloy , null , null , null , null

EFFECT OF MICROSTRUCTURE ON FATIGUE CRACK INITIATION OF SHOT PEENED COPPER AND BRASS

K.W.Xu , N.S.Hu and J.W.He(State-Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , China Manuscript received 26 August 1996)

金属学报(英文版)

The effect of microstructure on fatigue crack initiation was considered in the shot peened surface layer by eliminating the influence of compressive residual stress. Results indicate that the drastically deformed structure by shot peening would keep the dislocations from moving out of the surface and hold the dislocations inside the cell structure of copper or the palling structure of brass. The fatigue damage of intrusion and extrusion type could thus be depressed and the fatigue life is enhanced.

关键词: :shot peening , null , null

A NEW NON-UNIFORM YIELD PHENOMENON AND ITS MECHANISM

W.F. Zhang , Y.M. Chen and J.H. Zhu(State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , China)

金属学报(英文版)

A new non-uniform yield phenomenon is found during tension of austenite stainless steel at -190℃, which consists of elasto-plastic instability ξph and stress plateau ξL resulting from strain-induced martensite transformation. It is essentially different from non-uniform yield that is related to dislocation obstacles. The experimental results show that ξph and ξL increase with increaslng strain rate, and ξph, increases but ξL decreases with increasing prestmin.Tronsformation enengy of strain-induced martensite keeps a constant, 3.85×106J/m3, with increasing strain at the stages of both elasto-plastic instability and stress plateau.

关键词: non-uniform yield , null , null , null

ACTIVATION MECHANISM OF AMORPHOUS Ni_(63)Zr_(32)La_5 ALLOY HYDROGENATION CATALYST

X.K. Wang. N. F. Shen and G.J Lei(Dept. of Materials Science and Engineering , Zhengzhou Institute of Technology , Zhengzhou 450002 , China)H. C. Gu(Dept. of Materials Science and Engineering. Xi'an Jiaotong University , Xi'an 710049 , China Manuscript received 27 September 1995)

金属学报(英文版)

The catalytic activity of amorphous Ni_63 Zr_32 La_5 ribbon for hydrogenation of ethyne to ethylene can be greatly enhanced when the alloy ribbon is pretreated with dilute acid solution,heated under negative atmosphere pressure and subjected to hydrogen reduction successively. The change of surface state of the ribbon during the activation has been analysed by AES and XPS. The surface of as-received ribbon is covered with a thin film of La_2 O_3. After pretreatment. the surface concentrations of both Ni and Zr increase obviously, whereas the surface concentration of La decreases markedly.Finally, on the surface of activated catalyst the Ni and NiO disperse finely on the matrix consisting of oxides of both Zr and La and a small amount of fluorides of Zr and La.

关键词: :amorphous Ni_(63) Zr_(32) La_5 alloy;catalyst;activation mechanism

EFFECT OF SPECIMEN SIZE ON J_R RESISTANCE CURVE

H.P. Chen and Z.J. Deng (State Key Lab. for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , China)

金属学报(英文版)

The effect of specimen thinkness on JR resistance curve has been investigated using low and middle strength steels. As the J dominance regime is reached, the initial J-integral values, J(i), are definite even if the elastic component Ji(e) and plastic component Ji(p)vary with the thinkness of specimen. The wider the specimen width, the larger the Ji(e)/Ji and the smaller the Ji(p)/Ji. The crack propagation resistance, dJR/da and dJp/da, decreases, while dJe/da increases linearly with increasing specimen thinness.Based on the above experimental results, an empirical formula dJ/da = α+β. B is given, which can be used to evaluate the safety of practical structural components.A modified J-integral is presented, upon which a new view is Put forward that the increase in crack growth resistance is induced mainly by the increase in the plastic J-integral component with the crack propagation,

关键词: : fracture mechanics , null , null , null

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