The present work deals with the problem of a possible application of current in deformation processes. A literature survey has shown an existence of publications on the electroplastic effect in single-phase materials without phase transformations and the lack of works on a study of the current impact on the deformation behavior of materials undergoing a phase transformation. Therefore, the influence of current regimes (density and impulse duration) and current mode (direct, pulse or multiple-pulse) on the deformation behavior of TRIP steel in austenite-martensite and completely martensite states is studied. Methods of mechanical tests, X-ray diffraction analysis and scanning electron microscopy observations of fracture surfaces are used. In the absence of current the steel in austenite-martensite state displays a martensitic transformation during tension that leads to an excellent combination of mechanical properties -high ultimate tensile stress and preservation of the initial ductility. It is shown that in austenite-martensite state the shape of the stress-strain tension curve and the type of flow stress jumps caused by martensitic transformation and electroplastic effect depend on the current mode. Single current pulses exert practically no influence on the mechanical properties and deformation behavior in tension. The multiple-pulse and direct current cause a considerable thermal effect, decrease in the electroplastic effect and a suppression of the TRIP effect. As a result, both the ultimate tensile stress and elongation to failure decrease. The steel in martensite state displays no TRIP effect during tension with current due to the lack of a reverse transformation, and the elongation to failure sharply decreases. According to scanning electron microscopic observations, the failure mode of samples in both states, irrespective of current, corresponds to a mechanism of ductile cleavage or shear.Keywords: pulse current; deformation; fracture; phase transformation; tension; TRIP effect.
Подавление трип эффекта в метастабильных сталях электрическим токомСтоляров В.В. Работа связана с проблемой возможного применения тока при деформационных процессах. Литературный ана-лиз продемонстрировал наличие статей по электропластическому эффекту в однофазных материалах без фазовых превращений и отсутствие работ по исследованию воздействия тока на деформационное поведение в материалах, испытывающих фазовое превращение. В этой связи, исследовано влияние режимов (плотности и длительности им-пульса) и моды электрического тока (постоянного, импульсного, многоимпульсного) на деформационное поведение при растяжении ТРИП стали в аустенитно-мартенситном и полностью мартенситном состояниях. Использованы методы механических испытаний, рентгеноструктурного анализа и фрактографических наблюдений изломов ме-тодом сканирующей электронной микроскопии. В отсутствие тока сталь в аустенитно-мартенситном состоянии при растяжении испытывает мартенситное превращение, что приводит к отличной комбинации механических свойств -высокой прочности и со...
The static and fatigue strength properties of commercially pure VT1-00 (Russian standard) titanium and the Zr-2.5%Nb zirconium alloy have been studied after equal-channel angular pressing (ECAP). It is shown that the formation of submicrocrystalline (SMC) structure upon ECAP leads to significant strengthening, increases the service life in a high stress amplitude range and increases the fatigue strength relative to those typical of the annealed state. The specific features of the fatigue fracture mechanism in different structural states of materials are studied.
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