K.H. W. Seah(Dept. of Mechanical Engineering
,
National University of Singapore
,
10 Kent Ridge Crescent
,
Singapore 0511)R.S.Kulkari and S.C.Sharma (Dept. of Mechanical Engineering
,
R.V.College of Engineering
,
Mysore Road
,
Bangalore-560-059
,
Karnataka
,
Indi
材料科学技术（英文）
This paper reports some results obtained in an investigation to see how increasing the corundum dispersoid content from o% to 7% in a matrix of hiduminium alloy affects the tensile and compressive strengths, the hardness and the casting characteristics of the composite. The results show that as the corundum content is increased, ultimate tensile strength (UTS)- compressive strength and hardness increase remarkably, whereas fluidity of the molten composite during casting drops significantly. It was found that just a minute amount of corundum is sufficient to cause a fairly large change in the mechanical properties and the fluidity of the molten material.This drop in castability is one of the reasons why adding corundum beyond 7 percent is not recommended. If other factors are kept constant, the fluidity is seen to slightly improve if the pouring temperature of the molten metal were increased from 670 to 710℃
关键词:
HAN Qingyou HU Hanqi Beijing University of Science and Technology
,
Beijing
,
China [Originally published in ACTA METALL SIN (CHINESE EDN) 24 (5) 1988 pp B320—B324
,
received 29 August 1986
,
in revised form 5 March 1987]
金属学报(英文版)
The gradient of the equilibrium melting temperature distribution at the advancing liquid-solid interface of liquid side was derived.From which,a parameter,H,used for evaluating the abili- ty of grain refinement of solute elements was proposed.Experiments on Al-based alloys show that the grain size decreases as the value of parameter,H,increases.Such a dependance indi- cates that the parameter H can be used for choosing grain refiner.
关键词:
solute elements
,
null
Q.M. Yu
,
B.F. Hu
,
C.C. Jia
金属学报(英文版)
Phase stability of four different chemical component Fe-Cr-Mn(W, V) alloys are in-vestigated by experimental method and thermodynamic model in this paper. It is indi-cated that the main phase of four alloys after aged under 623, 673, 773K for 200h areaustenitic phase. The results of Thermo-Calc, which are based on Gibbs energy, showthat the phases of four alloys underthe same temperature as experimental method aresingle austenitic phase. The results of experimental method and Thermo-Calc agreewell.
关键词:
phase stability
,
null
,
null
,
null
XU Yongbo HA Kuanfu WANG Zhongguang YANG Chunsong DAI Zhongling Laboratory for Fatigue and Fracture of Materials
,
Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
110015
,
China.Jilin University
,
Changchun
,
130023
,
China.To whom correspondence should be add
材料科学技术（英文）
An investigation has been made of the disloca- tion distribution and dislocation free zone near the crack tip in bulk Fe-3% Si single crystal during deformation in SEM.It has been found that a number of dislocations were emitted from the crack tip during deformation.After that,the dislocations moved rapidly away from the crack tip,which indi- cated that they were strongly repelled by the stress field at the crack tip.Between the crack tip and the plastic zone there is a region of dislocation-free, which is referred to as dislocation-free zone (DFZ). The length of DFZs is roughly estimated 100 μm which is much longer than that found in thin foil specimen.The variation of dislocation density as a function of the distance from the crack tip was measured,which showed that the dislocations are inversely piled up in the plastic zone.The length of DFZs increased with both the length of pre-crack and the amplitude of applied stress.
关键词:
dislocation
,
null
,
null
,
null
WANG Ruikun SUN Lihong LI Dongpei YING Qiming T.Takeyama General Research Institute for Non-Ferrous Metals
,
Beijing
,
China [Originally published in ACTA METALL SIN (CHINESE EDN) 24 (5) 1988 pp B353—B358
,
received 6 May 1987
,
in revised form 6 February 1988] T.Takeyama is an emeritus professor of HOKKAIDO University
,
Japan
,
and now is a technical adviser of GRINFM
金属学报(英文版)
The magnetic domain structure and related magnetic properties of (NdPr)_(16)Fe_(76)B_8 permanent magnet have been studied by colloid-SEM method.In thermally demagnetized state,the ma- trix grains in the magnet generally exhibit multidomain structure,i.e.,180° plate-like indi- vidual domain and a few spike-like or maze-like domains.The average width of the domain measured was 1.5μm.Grain size of single-domain was observed to be generally about 1μm and only a few up to 3μm.The results calculated are:the domain wall energy γ=36 MJ/m~2,the exchange constant A=4.5×10~(-11)J/m,the domain wall width δ=15.7nm, and the critical grain diameter of single-domain D_c=0.5μm.The dependence of high magnet- ic field gradient at grain boundaries in different magnetization directions in the adjacent mag- netic domains located on both sides of grain boundaries and the effect of microstructure on the values of K,A and δ were discussed.
关键词:
Nd-Fe-B permanent magnet
,
null
,
null
