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
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
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
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
Hongtao SUN
,
Hongfang WANG
,
Liangying ZHANG and Xi YAO(Electronic Materials Research Laboratory
,
Xi'an Jiaotong University
,
Xi'an
,
710049
,
China)
材料科学技术（英）
Under the mechanically free and clamped boundary conditions, electromechanical resonances of ceramic multilayer capacitors are calculated using vibration and piezoelectric equations. Multilayer capacitors made of ferroelectric BaTiO3 and Pb(Mg1/3Nb2/3)O3 ceramics have been used to examine the theoretical calculation. Frequency spectra of impedance and phase angle, capacitance and loss tangent of the capacitors under dc bias fields are carefully measured. A sudden change around the resonant frequency is observed in these spectra. A damped resonance indicates a defective capacitor while an undamped resonance is corresponding to defect free.Experimental results suggest that it is possible to use the spectra as a real time nondestructive evaluation method.
关键词:
Weidou ZHU and Haicheng GU(Dept. of Materials Science and Engineering
,
Xi'an Jiaotong University
,
Xi'an
,
710049
,
China)
材料科学技术（英）
Thin metallic layers (~ 2 μm) of Ni were deposited on polycrystalline Al2O3. ZrO2 and (Ce-TZP)+Al2O3 ceramic substrates. and further irradiated with pulsed excimer (Xeno chloride) laser pulses. The laser energy density was varied from 0.21 to 0.81 J / cm2 to optimize bending strength. For ZrO2 ceramic, it was found that the strength increases from 530 to 753 MPa at 0.51 J / cm2 irradiation. For Al2O3 and (Ce-TZP)+ Al2O3 the fracture strength also increases in varying degree. The causes of strength increment were discussed.
关键词:
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
LIU Yumen Department of Materials Science and Engineering
,
Xi'an Jiaotong University
,
Xi'an
,
China.
材料科学技术（英）
The variations of the dislocation structures in the quench and 650℃ tempered steel with increase of elongations have been investigated by using transmission electron microscopy. In the small elongation stage, the boundaries between ferrite and carbide in this steel can release dislocations. As the elongations increase, the moving dislocations in the ferrite slip onto the carbides. Then, the interaction between moving dislocations and dislocations released from this boundaries, and the interaction between the dislocations moving to the carbides in every slip plane occurs. Thereby, the dislocation tangles around the carbides can be formed. In the large elongation stage, the dislocation tangles with high dislocation density and the developed dislocation cells are formed.
关键词:
plastic deformation
,
null
,
null
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
