Abstract: The mathematical models for secondary dendrite arm isothermal coaening kinetics are developed for multicomponent. alloys on the basis of four physical models previously proposed. Calculations based on these models show qualitive agreement with experiment conducted by Nobuy-uki Moriet on Al-Cu-Si, Al-Cu-Fe and Al-Cu-Mn alloys. It shows that the increasing of solute contents favors the thinning of secondary dendrite arms under the condition that the local solidification times are kept constant for multicomponent alloys during solidification processing.
Abstract: The structure analyses of two GH36 superalloy turbine disks with different heat treatments were conducted by thin foil TEM. The preci-tates in GH36 super alloy were identified as VG, M23C6 and NbC by SAD. Electron diffraction patterns show the orintation relationship between precipitates and matrix as following:\[\begin{array}{l}{{\rm{[011]}}_{{\rm{vc}}}}{\rm{||[011}}{{\rm{]}}_{\rm{M}}}{\rm{||[011}}{{\rm{]}}_{{{\rm{M}}_{{\rm{23}}}}{{\rm{C}}_{\rm{6}}}}}\\{{\rm{[111]}}_{{\rm{vc}}}}{\rm{||[111}}{{\rm{]}}_{\rm{M}}}{\rm{||[111}}{{\rm{]}}_{{{\rm{M}}_{{\rm{23}}}}{{\rm{C}}_{\rm{6}}}}}\\{{\rm{[200]}}_{{\rm{vc}}}}{\rm{||[200}}{{\rm{]}}_{\rm{M}}}{\rm{||[200}}{{\rm{]}}_{{{\rm{M}}_{{\rm{23}}}}{{\rm{C}}_{\rm{6}}}}}\end{array}\]Moire patterns and dark field show that the size of VC precipitates after normal heat treatment varies from 3 to 12nm. The size of VC after superimposed higher temperature aging grows in a few nm larger and more M23C6 carbide precipitates in alloy than norma heat treatment. Thus, the yield stress and stress rupture strength decrease, but the stress rupture notch sensitivity has been improved.
Abstract: Spinodal decomposition and magnetic hardening of Fe-23Cr-15Co-0.5Ti alloy were studied by magnetic measurement, transmission electron microscopy (TEM), Mossbauer effect and observation of magnetic domains after thermomagnetic treatment (TMT) and multiple step aging.
Abstract: High 1Hc (>30KOe) has been obtained in Sm (Co Cu Fe Zr)7.4 magnet after aging at 850 ℃ for a long period of time. Coercivity, initial magnetization curves, magnetic domain patterns, microstructures and microstres of the diffrent aging time at 850 ℃ are Studied using magnetic measurement, Kell technical and transmisson electron microscopy. The action of "Z" phase, zonal structure and grain boundary precipitates on domain walls are discussed and a machanism of heterogeneous pinning at the high coercivity is suggested.
Abstract: The black structure, non-mar tensite structure in Carboni trided case, is easy to occure in boron steel, when the heat treatment process is out of control, which reflects the decline of hardenability of case material. There are two kinds of black structure, surface black structure and transition region black structure,caused respectively by the inner-oxidation of alloying elements and the formation of carbide and nitride at the surface, and by the redistribution and variation of occurrence state of boron throughout the case. In order to prevent the both black structures, high carbonitriding temperature, later supply of ammonia, large amount of kerosene and small amount of ammonia supplied in carbonitriding stage, and rapid quenching after the treatment are recommended.
Abstract: The effect of rare earth elements Nd and La on hydrogen permeation in pure iron was studied by means of a Davanathan apparatus Experimental results indicate the diffusion coefficient reduces as the amount of solute Nd or La increases. It's concluded that Nd or La is a reversible Shallow trap of hydrogen pemeation in iron The binding energy of hydrogen around solure Nd is 4.4 kcal/mol and the diffusion activation energy of hydrogen is 6.1 kcal/mol.
Abstract: The flexural vibration equation of a beam under stress is set up. The solution of the equation indicates E=C (α)ω2, where E stands for the apparent Young's modulus, C for a function of stress, and ω for the intrinsic frequency of sample. If the resonant frequencies of the first tone and the third one are measured at about same time, E and σ can be calculated. The change of the apparent Young's modulus after charging with hydrogen is difined as ΔE=ΔE1 (H) + ΔE2, where ΔE1 (H) has relation with the change of the perfect crystal interatomic cohesive force and ΔE2 is induced by the change of stress. An artificially partial stress relaxation test was done to measure ΔE2. The results show that during ageing after both charging with hydrogen and artificial stress releasing, the apparent modulus increased by 0.1-0.3%, i.e 0ΔE=ΔE2. Thus, the ΔE1 (H) associated with the interatomic cohesive force does not evidently change during the ageing with evolving hydrogen of 7-8 wppm, i.e. hydrogen of 7-8 wppm does not significantly decrease the interatomic cohesive force of α-Fe. The Forster's horizontal free-free bar apparatus was also used to measure the change of Young's modulus of a-Fe caused by hydrogen. The same conclusion was obtained.
Abstract: This article put forward a Fourier synthesis method of X-ray diffraction profile analysis for determination of grain size and microdistor-tion. Comparing with the, other existing methods, the hypotheses applied in this method is minimum.
Abstract: According to the method of activity calculation in binary system containing compounds from standard entropy of formation of compounds[1], further using the standard heat of fo rmationof compounds, we deduced the new formula which was also for the compound system. The new formula is\[{\rm{dln}}{{\rm{\gamma }}_{\rm{A}}}{\rm{= - }}\frac{{{\rm{\Delta }}{{\rm{H}}_{\rm{f}}}^{\rm{0}}{{\rm{N}}_{\rm{B}}}}}{{{\rm{R}}{{\rm{T}}^{\rm{2}}}{\rm{(x}}{{\rm{N}}_{\rm{B}}}{\rm{ - y}}{{\rm{N}}_{\rm{A}}}{\rm{)}}}}{\rm{dT - dln}}{{\rm{N}}_{\rm{A}}}\;\;\;\;\;\;\;\;(1)\]here ΔHf0 is standard heat of formation of compounds; x,y.is stoichi-ametric factors of the component A,B respectively; NA NB is mole fraction of the components A. B respectively; γA. γB is activity coefficient of components A,B at liquidus temperature. In the binary system Au-B1 the activity values calculated by our fo-mula and by Chou's formula are compared with the measured values. They were very well in agreement on the values. In this paper the values of the binary system Al-La is calculated using our new formula. The results are discussed briefly.
Abstract: Applying solid slag Cakes of rare earth oxide as a desulphurizinga gent as well as a modifying agent and under Condition of Ar-blowing, a hy-pereutictic hot metal of high Sulphur content (s=0.100%) has been mo-difyied. Experiments are made at 1450 ℃ for about 30~35 minutes. Changeing laws of chemical composition in hot metal and relationship between graphite morphogy and contentof RE, CE in casting are abta-ined. Results indicate that the RE% ≤ (CE%-4.30%)/25 and the RE% ≥ (CE%-4.30%)/25 canbe abtained vermicalar cast iror and nodular cast iron respectively under hypereutectic hot metal. with regrad to disuph-urizing reaction and redwction reaction of rare earth oxrde, discussion and thermodynamic calculation have been Carried out. The results point out that the above mentioned reaction are all established thermodyra-mically umder the experimental condition.
Abstract: Fractional programming appears often in the management model. It can be Solved by the Gilmore-Gomory algorithm. In our paper. we have constructed counterexample Showing that the Gilmore-Gomory algorithm may produce cycles, so that the computation is impossible. In this paper. we also give new finite pivoting rules and show that using this new pivoting rules cycles are avoided.
Abstract: In the research of facture mechanics, although straight line crack is the most simple and useful crack model,One of the reason is that straight line crack can expend and changeinto bent line crack in the complex stresses condition.it is difficulty to calculate the SIF of bent crack. so it is also difficulty to research co mplex fatique extention law. In this paper, the bent cracks were studied by the calculation of the SIF of a bent crack which contained three bent point specimen, the computations that verified by experimenting was applied to the research of complex type fatique extension law.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
