Effect of rolling conditions on ferrite refinement of low-carbon steel
Refinement of the ferrite grains provides a promising approach to simultaneously improving both the strength and the toughness of steels. Among recent techniques to obtain ultrafine ferrite, dynamic strain induced transformation (DSIT) is used. This type of treatment is sensitive to steel composition, deformation temperature, the prior austenite grain size, strain and cooling rate. This work is aiming to improve the mechanical properties of steels using ferrite grain refining through trials on industrial scale using a compact strip production plant (CSP) with hot strip mill (HSM) containing six stands F1-F6 in EZDK Steel Company. The chemical composition of the trials was C (~0.046), Si (0.073) Mn (0.50) and Ti (0.008). The effect of final deformation temperature of 750, 775, 800 and 815°C on the microstructure and mechanical properties was studied. In addition the effect of strain rate variation at the final two rolling stands was correlated with the ferrite refining mechanisms. The ferrite grain size attained after refining varies from 10 μm to be 6 μm. Yield and tensile strength increased slightly through changing deformation temperature, with the advantage of keeping almost the original high ductility. Toughness of the processed steel increased with ferrite grain refining.
On the ferrite refinement during the dynamic strain-induced transformation: A cellular automaton modeling
Two-dimensional cellular automaton modeling has been performed to investigate the mechanism of ferrite refinement during the dynamic strain-induced transformation (DSIT) from austenite (gamma) to ferrite (alpha) in a low-carbon steel. The simulated results indicate that the refinement of ferrite grains derived from the DSIT could be interpreted in context of "un-saturated" nucleation and limited growth. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
A Critical Assessment on Functional Attributes and Degradation Mechanism of Membrane Electrode Assembly Components in Direct Methanol Fuel Cells
Direct methanol fuel cells (DMFC) are typically a subset of polymer electrolyte membrane fuel cells (PEMFC) that possess benefits such as fuel flexibility, reduction in plant balance, and benign operation. Due to their benefits, DMFCs could play a substantial role in the future, specifically in replacing Li-ion batteries for portable and military applications. However, the critical concern with DMFCs is the degradation and inadequate reliability that affect the overall value chain and can potentially impede the commercialization of DMFCs. As a consequence, a reliability assessment can provide more insight into a DMFC component’s attributes. The membrane electrode assembly (MEA) is the integral component of the DMFC stack. A comprehensive understanding of its functional attributes and degradation mechanism plays a significant role in its commercialization. The methanol crossover through the membrane, carbon monoxide poisoning, high anode polarization by methanol oxidation, and operating parameters such as temperature, humidity, and others are significant contributions to MEA degradation. In addition, inadequate reliability of the MEA impacts the failure mechanism of DMFC, resulting in poor efficiency. Consequently, this paper provides a comprehensive assessment of several factors leading to the MEA degradation mechanism in order to develop a holistic understanding.