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In terms of continuum mechanics a twin is represented by the sudden appearance of a shear eigenstrain state in a distinct region. The corresponding elastic strain energy, the interface energy and the energy dissipated due to the irreversible character of the deformation process are investigated. If the total amount of these energy terms, spent by the twinning process, can be provided by the interaction energy of an external and/or internal stress state with respect to the twin shear eigenstrain, then either a deformation twin band or a twin nucleus may appear. Realistic estimations of the dimensions of deformation twins can be presented. This energetic interpretation of twinning is experimentally demonstrated for intermetallic TiAl.

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The purpose of this paper is to investigate the fatigue behavior of precipitation-strengthened Cu‒2.55Ni‒0.55Si alloy, modified by the addition of 0.25 Cr and 0.25 Zr (wt%), using mechanical and fractographical studies to reveal the effect of microstructural features on the fracture.

For strengthening, cast and hot forged alloy was subjected to solution annealing at 900°C for 60 min, followed by quenching in water and then aging at 490°C for 180 min. Precipitation-hardened alloy was exposed to fatigue tests at R=−1 and different stress levels. All fracture surfaces were examined within the frame of fractographical analysis.

Fine Ni-rich silicides responsible for the precipitation strengthening were observed within the matrix and their interactions with the dislocations at lower stress level resulted in localized shearing and fine striations. Although, by the addition of Cr and Zr, the matrix consisted of hard Ni, Zr-rich and Cr-rich silicides, these precipitates adversely affected the fatigue behavior acting as nucleation sites for cracks.

These findings contribute to the present knowledge by revealing the effect of microstructural features on the mechanical behavior of precipitation-hardened Cu‒Ni‒Si alloy modified by Cr and Zr addition.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued

The purpose of this study is to investigate the effect of prior cold work after annealing and thermal ageing on intergranular corrosion or sensitization of Cr-Mn austenitic stainless steel (ASS) is necessary. Such a study is particularly important because ASS are mostly used and welded in mill-annealed condition, which is equivalent to fully annealed material with some cold worked (CW).

The effect of 15% CW of 202 ASS were investigated using microstructural (optical microscope), mechanical (grain size and hardness) and electrochemical methods (double loop electrochemical reactivation [DLEPR]) followed by thermal ageing (800°C, 900°C and 1000°C).

X-ray diffraction analysis shows the presence of martensite in CW samples. The increase in martensite formation (800°C and 900°C) can be observed with the variation of thermal ageing (TA) duration (1, 2 and 3 h). However, there was decreased in the formation of martensite at the temperature of 1000°C because of martensitic reversal. The DLEPR test result shows higher degree of sensitization (DOS) for 800°C and 900°C but for 1000°C, there was re-homogenization of samples which leads to lower DOS (thermal ageing for 1, 2 and 3 h).

For 300 series steel, there are various literature available for the effect of cold work on mechanical properties and DOS. However, no one has investigated the effect of cold work and thermal ageing on the sensitization of 202 Cr-Mn ASS.

Under this heading will be published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued.—Ed,

A RADAR DETECTING SYSTEM, the AN/ALR‐47 counter‐measures receiving set, has the capability for very long range detection. It is manufactured by the IBM Electronics Systems Centre in Owego.

The purpose of this study was to investigate the effects of deformation-induced martensite on electrochemical corrosion behaviors of 304 austenitic stainless steel in a simulated primary water environment of a pressurized water reactor nuclear power plant with boric acid and lithium hydroxide contaminated with chloride by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott–Schotty curves and X-ray photoelectron spectroscopy (XPS).

The effects of deformation-induced martensite transformation on electrochemical corrosion behaviors of 304 austenitic stainless steel was investigated in a simulated primary water environment of a pressurized water reactor nuclear power plant with boric acid and lithium hydroxide contaminated with 0.1 M Cl⁻ by potentiodynamic polarization, EIS, Mott–Schotty curves and XPS in this paper.

The results revealed that the martensitic phase contents increased with the level of cold deformation. The general corrosion current density and the corrosion potential increased and decreased, respectively, with the increase of cold deformation degree. However, the pitting potential decreased as the cold deformation increased up to 20 per cent, then a slight increase was observed at 35 per cent cold working. It was found from Mott–Schottky curves and XPS analysis that as the cold deformation degree increased from 0 to 35 per cent, the doping concentrations of the oxide films increased; however, the film thickness decreased, which indicates that both density and integrity of the films are degraded significantly as the deformation degree increases, and this ultimately contributes to the significant increment of the general corrosion rate and reduction of the pitting corrosion resistance.

The effects of deformation-induced martensite transformation on electrochemical corrosion behaviors of 304 austenitic stainless steel was investigated in a simulated primary water environment of a pressurized water reactor nuclear power plant with boric acid and lithium hydroxide contaminated with 0.1 M Cl⁻ by potentiodynamic polarization, EIS, Mott–Schotty curves and XPS in this paper.

Fine diamond powders, in some cases composed of particles smaller than one micron, are assuming ever increasing importance, especially as the cost of conventional abrasives rises disproportionately. This article looks at the advancing technology behind natural and synthetic micron diamond powders and their significance in the automated industry of today

Deficits in fiscal and current account balances in a large number of countries reveal interesting implications of the causal relationship between internal and external imbalances. Empirical evidence about the occurrence of so-called twin deficits or twin surpluses provides crucial information about the validity of an intertemporal approach. However, most recent dynamic cyclical changes during the crisis period revealed many questions about the direct interconnection between macroeconomic performance and twin imbalances. In the paper we observe substantial features of twin imbalances in European transition economies. Event study (identification of large fiscal and current account changes and their parallel occurrence) and vector auto-regression methods will be employed to examine key aspects of twin imbalances. Our results suggest that current account deteriorations were predominately associated with negative public investment and savings balances (fiscal deficits), while current account improvements were predominately associated with positive private investment and savings balances, confirming empirical evidence about twin deficits in European transition economies.