Determination of Transformation Induced Heat Transfer Coefficients in Mechanical Properties of Powder Metallurgy Steels
2 Abstract: Powder metallurgy has been used for the manufacture of fully dense, which have not reacted composites consisting of a matrix of copper containing 50 -60 vol% particles with negative thermal ZrW2O8 expansion. On cycling between 25 and 300°C, the compounds showed coefficients thermal expansion which varies rapidly with temperature and significantly larger than expected by theory. Improvements in adhesion strength and thermal properties of composite materials have been achieved in atomized copper alloy with small additions of chromium to increase the interfacial bonding in composite Cu / diamond from a nano-sized thin Cr3C2layer.
Singly dispersed carbon nanotube/aluminum composites fabricated by powder metallurgy combined with friction stir processing
Carbon nanotube (CNT)/aluminum composites were fabricated by a combination of powder metallurgy and subsequent friction stir processing (FSP). Microstructural observations indicated that the CNTs were singly dispersed in the composites. The CNTs tended to be dispersed along grain boundaries resulting in a much finer grain size. Although the CNTs were shortened and some Al4C3 formed in the matrix, the layer structures of the CNTs were well retained. Raman spectroscopy also showed that the damage to CNTs during FSP was not severe. Compared to that of unreinforced Al, the yield strength of 1 wt.% and 3 wt.% CNT/Al composites increased by 23.9% and 45.0%, respectively. A strength equation relating with load transfer and the grain refinement was proposed to describe the increase of the yield strength of the composites. (C) 2011 Elsevier Ltd. All rights reserved.
Constitutive modelling for high temperature behavior of 1Cr12Ni3Mo2VNbN martensitic steel
Abstract The deformation behavior of 1Cr12Ni3Mo2VNbN martensitic steel in the temperature range of 1253 and 1453 K and the strain rate range of 0.01 and 10 s−1 are investigated by isothermal compression tests on a Gleeble 1500 thermal–mechanics simulator. Most of the stress–strain curves exhibit a single peak stress, after which the stress gradually decreases until a steady state stress occurs, indicating a typical dynamic recrystallization (DRX) behavior of the steel under the deformation conditions. The experimental data are employed to develop constitutive equations on the basis of the Arrhenius-type equation. In the constitutive equations, the effect of the strain on the deformation behavior is incorporated and the effects of the deformation temperature and strain rate are represented by the Zener–Holloman parameter. The flow stress predicted by the constitutive equations shows good agreement with the experimental stress, which validates the efficiency of the constitutive equations in describing the deformation behavior of the material.