Changes in the state of sulfides and impact toughness of the quenched 40KhGM steel upon heat treatment in the austenitic region

The impact toughness of the quenched 40KhGM steel has been investigated as a function of the heat treatment conditions in the austenitic region. The maximum impact toughness was observed after heating to 1300°C, intermediate annealing at 1050°C, and quenching with low-temperature tempering. According to the results of the fractographic and electron-microscopic examinations, the high impact toughness is due to the specific type of the manganese sulfide precipitation from the γ solid solution. The results of a theoretical estimation of the average sulfur solubility in the γ solid solution are presented.     

Adiabatic Coupling Constant of Nitrobenzene–<Emphasis Type="Italic">n</Emphasis>-Alkane Critical Mixtures. Evidence from Ultrasonic Spectra and Thermodynamic Data

Ultrasonic spectra of mixtures of nitrobenzene with n-alkanes, from n-hexane to n-nonane, are analyzed. They feature up to two Debye-type relaxation terms with discrete relaxation times and, near the critical point, an additional relaxation term due to the fluctuations in the local concentration. The latter can be well represented by the dynamic scaling theory. Its amplitude parameter reveals the adiabatic coupling constant of the mixtures of critical composition. The dependence of this thermodynamic parameter upon the length of the n-alkanes corresponds to that of the slope in the pressure dependence of the critical temperature and is thus taken another confirmation of the dynamic scaling model. The change in the variation of the coupling constant and of several other mixture parameters with alkane length probably reflects a structural change in the nitrobenzene–n-alkane mixtures when the number of carbon atoms per alkane exceeds eight.     

Elements of the dislocation theory and its significance in metal science part 2

Metal Science and Heat Treatment -     

Does the Viscosity Exponent Derive from Ultrasonic Attenuation Spectra?

Based on a representation of the sound velocity of critical liquids in terms of a frequency-dependent complex specific heat at constant pressure, a simple relation between the low-frequency normalized sonic attenuation coefficient and the correlation length of fluctuations is derived. This relation provides a promising alternative for the determination of the dynamics exponent and thus the critical exponent of the shear viscosity. Sonic attenuation data from the literature, measured at frequencies down to 50 kHz, are re-evaluated with a view of the viscosity exponent determination. It is found that only in a small temperature range, the major requirement of the approach is fulfilled with the available data. Close to the critical temperature, the frequencies of measurement are still insufficiently small as compared to the inverse relaxation time of order parameter fluctuations. Criteria for future experiments are discussed briefly.     

Thermophysical and acoustic properties of aqueous solutions of the pluronic PE6400 copolymer

Experimental results of investigations of the specific heat and the velocity of sound in aqueous solutions of the Pluronic PE6400 copolymer have been presented. Phase transitions, phase states, and possible physical mechanisms of the effects have been discussed based on these results. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 158–163, May–June, 2006.