A new method of automatic polishing on curved aluminium alloy surfaces at constant pressure

This paper presents original research results of automatic polishing on curved surfaces of aluminium alloy moulds at constant pressure. The automatic polishing of aluminium alloy material is achieved. A parameter S is defined, which can express the comprehensive influential factors in the automatic polishing process and give a relationship among the polishing quality and the various machining variables. Based on this, a new method for comprehensive control of polishing quality is suggested.     

Phase transitions of two isomorphous two-dimensional conductors (BEDT-TTF)2ClO4X0.5 (X = C2H3Cl3 and C2H4Cl2)

The metal-semiconductor (or metal-metal) transitions of two isomorphous BEDT-TTF (ET) compleses, (ET)₂ClO₄X_0.5 With an asymmetric X = C₂H₃Cl₃ and a symmetric C₂H₄Cl₂ molecule are investigated. The order-disorder configuration changes of the ethylene groups in ET molecules, in addition to the disorder introduced by the asymmetric structure of the molecule for the former complexes, play an important roles in determining the nature of the transitions.     

Quenching stress in plasma sprayed coatings and its correlation with the deposit microstructure

Quenching stress arises within a thermally sprayed splat as its thermal contraction after solidification is constrained by the underlying solid. Dependence of the quenching stress in plasma-sprayed deposits of Ni-20Cr alloy and alumina on the substrate temperature during spraying was discussed in conjunction with the change in the nature of the interlamellar contact between splats. It was found by mercury intrusion porosimetry and observation of cross sections of impregnated deposits that the interlamellar contact is improved significantly by raising the substrate temperature during deposition from 200 to 600 °C. The positive dependence of the quenching stress on the substrate temperature in this temperature range was attributed to a stronger constraint against thermal contraction of sprayed splats after solidification due to the improved contact.     

Texture of primary recrystallization on nonoriented electrical steel sheet with phase transformation

The magnetic properties of nonoriented (NO) electrical steel sheet are commonly improved if the texture of their products possesses “cube texture” (e.g., {100 〈0vw〉, “goss texture”) (i.e., 110〈011〉, and less 222 texture). Industrially “cube type” has not been obtained, but “goss texture” has been. In a greater or lesser degree, {222} texture exists. To improve “goss texture” and reduce 222 texture, the grain size of the material prior to cold rolling should be larger. When the grain size before cold rolling is larger, during primary recrystallization, “goss texture” is enriched, 222 texture is decreased, and the grain grows so easily that higher induction and lower core loss can be obtained. This does not depend on the presence of phase transformation. In case of NO steel with phase transformation, heat treatment before cold rolling has been done below the austenite transition temperature (Acin1) in order to prevent the fine grain size caused by α → γ(+α) → α transformation. By using material that was heated over Acin1 and cooled with changing cooling rates, this study describes (a) the relationship between textures before cold rolling and the texture of the final product, and (b) the development of the magnetic properties.     

Finite-element simulation of moving induction heat treatment

An efficient finite-element procedure with a remesh scheme has been developed for the analysis of the moving induction heat treatment process, wherein relative motion occurs between the coil and the workpiece. In this procedure, the magnetic field is first simulated by using an updated mesh that tracks the moving coil position; the moving heat source within the workpiece material is derived from the magnetic field. The heat equation is then solved to obtain the temperature field created by the heat source. The procedure has been applied to calculate the temperature distributions in 1080 carbon steel cylinders during induction heating. The calculations have been validated by comparison with analytical solutions for the temperature distribution obtained using Green’s function methods. Finally, the temperature, residual stress, and microstructure distributions in quenched 1080 steel cylinders have been obtained using the finite-element procedure. Quenching of the heated cylinders, by both a moving cooling ring and a stationary liquid bath, has been analyzed. The finite-element procedure presented incorporates temperature-dependent material properties, phase transformations occurring in the 1080 steel, the change in magnetic permeability of the 1080 steel at the Curie temperature, and an elastoplastic stress model based on a mixed hardening rule. The simulation results demonstrate that the finite-element procedure could be applied to a variety of moving induction heat treatment problems to determine the residual stress and microstructure distributions in the heat-treated component. It also could be used in the design of process parameters and coils.     

On the possibility of scandium alloying of copper-containing aluminum alloys

Scandium alloying of aluminum alloys can substantially improve their operating properties and weld-ability. Commercially scandium-alloyed alloys have been developed for the Al - Mg, Al - Zn - Mg, and Al - Mg - Li systems. The scandium alloying of aluminum alloys containing copper as an alloying component should be performed carefully, because scandium can produce a chemical compound with copper. This worsens the strength properties of preforms and decreases their plasticity and fracture toughness due to the increased volume fraction of the excess phases. In this work, conditions for scandium alloying are determined for the copper-containing alloys D16 and 1933.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 23 – 27, February, 1995.     

Effect of the composition on the hardenability and properties of complexly alloyed steel for large-size parts

Large-sin parts are usually produced from steels with high hardenability. Intermediate-carbon improved chromium-nickel steels containing 1–3% Ni are used successfully for this purpose in Ukraine and in foreign countries. However, nickel is an expensive and scarce alloying element. The present work is devoted to steels with different compositions with the aim of choosing the most suitable one for large-size parts. The effect of alloying elements on the hardenability and mechanical properties of steels is investigated. A mathematical model is obtained.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 13–17, May, 1995.     

Segregation of impurities,temper brittleness,and hydrogen embrittlement of steel 30KhNMA with different concentrations of molybdenum

In recent years practical and scientific interest in investigating segregation processes to assess the mechanism of steel embrittlement by impurity elements has grown. This interest was noticeably stimulated by industrial use of new metallurgical technologies that ensure higher purity of steel with respect to impurity elements. It has become possible to decrease the content of expensive molybdenum due to the higher purity of steels without substantial change in their properties. In the present work the structure and properties of steel 30KhNMA with conventional and elevated purities, standard and reduced concentrations of molybdenum, and microadditions of V, Ti, and Nb are investigated.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 21–24, May, 1995.     

Electrical anisotropy of α-(BEDT-TTF)2KHg(SCN)4

The transverse magnetoresistance of α-(BEDT-TTF)₂KHg(SCN)₄ was investigated with the magnetic field rotated within a conducting ac-plane. It was found that the magnetic-field-orientation dependence of the magnetoresistance in the weak-field limit, ΔR(B,θ), has the form ΔR(B,θ) = B²(psin²(θ − θ_min) + qcos²(θ − θ_min), where θ is the angle betweeen a-axis and magnetic field direction and (p, q, θ_min) are temperature-dependent parameters. By examining the results based on the classical theory of magnetoresistance, it was concluded that the electrical anisotropy within be-plane is 3.5 4.5 and 2.5 3.0 above and below the phase transition at 10 K, respectively.     

A drag-link drive of mechanical presses for precision drawing

The augmented Lagrange multiplier method has been used to synthesize the dimensions of a drag-link drive of mechanical presses for precision drawing. The objective functions include the maximum normal force on the guide, mean mechanical advantage, variance of the drawing velocity, etc. The constraints include the working velocity for drawing, variance of the working velocity for precision drawing, time ratio, etc. Based on the concept of kinematic coefficients, a method is proposed to provide suitable initial guesses of the optimization. The drag-link drive thus synthesized has performance superior to an existing press for precision drawing.