Samuel A. Awe; Salem Seifeddine; Anders E. W. Jarfors; Young. C. Lee; Arne K. Dahle
Abstract
In a quest for developing new lightweight metal alloys that can perform excellently at elevated-temperatures (from 300°C to 400 °C), a ternary eutectic Al-Cu-Si alloy was exploited to gain a deeper understanding of the alloy system and its suitability for high temperature applications. The studied ...
Read More
In a quest for developing new lightweight metal alloys that can perform excellently at elevated-temperatures (from 300°C to 400 °C), a ternary eutectic Al-Cu-Si alloy was exploited to gain a deeper understanding of the alloy system and its suitability for high temperature applications. The studied alloys, with chemical composition of Al-27%Cu-5%Si (by weight percent) with Ni addition in the range of 0 to 1.5%wt, were cast in a rapid solidification casting technique. The solidification characteristics of the alloy was studied using the Thermo-Calc software. Microstructures were characterized in a scanning electron microscope coupled with energy dispersive spectrometry (SEM-EDS). Finally, the elevated-temperature tensile properties of the alloys were investigated. Comparing the microstructures and mechanical properties of the Al-Cu-Si(-Ni) alloys with conventional A319 Al- alloy, the refined microstructure with dispersed Ni intermetallic particles formed in the as-cast Al-Cu-Si(-Ni) alloys delivers improved elevated temperature properties. In particular, the yield strength and ultimate tensile strength of the new alloy with 1.5% Ni at 400˚C were observed to be 220% and 309% higher, respectively, than for conventional A319 reference alloy.
Andrea Di Schino; Paolo Emilio Di Nunzio; Josè Maria Cabrera
Abstract
Aim of this paper is to analyze the effect of manganese percentages on steel compositions. Laboratory as cast materials, in particular designed for Quenching and Partitioning process (Q&P), are here considered. The considered steel chemical composition was that of a 0.15C with 1.5Si, two different ...
Read More
Aim of this paper is to analyze the effect of manganese percentages on steel compositions. Laboratory as cast materials, in particular designed for Quenching and Partitioning process (Q&P), are here considered. The considered steel chemical composition was that of a 0.15C with 1.5Si, two different Mn contents and with no significant Al content. Two-Step Q&P heat treatments were carried out in laboratory by means of dilatometric tests. X-ray diffraction measurements have been carried out aimed to assess the retained austenite volume fraction. The tensile properties of the quenched and partitioned materials were analyzed. Results showed a marked dependence of strength, ductility and strain capacity values on heat treatment conditions. In the case of higher austenite contents, higher uniform elongation values were found. Higher tensile properties were found in the case of higher Mn steel with respect to the lower Mn one. The main novelty of this paper consists in applying Q&P to low carbon (low hardenability steel) showing the effect of such a process on mechanical properties of steels usually adopted for automotive applications.
J. Jayaramudu; S.C. Agwuncha; S.S. Ray; E. R. Sadiku; A. Varada Rajulu
Abstract
In the present work, natural Polyalthiacerasoide woven fabrics were extracted from the bark of the tree and using these woven fabrics/glass fibre as reinforcements and epoxy as matrix the hybrid composites were prepared by the hand lay-up technique, at room temperature. The effect of alkali treatment ...
Read More
In the present work, natural Polyalthiacerasoide woven fabrics were extracted from the bark of the tree and using these woven fabrics/glass fibre as reinforcements and epoxy as matrix the hybrid composites were prepared by the hand lay-up technique, at room temperature. The effect of alkali treatment of Polyalthiacerasoide fabrics on the chemical structure and morphology was examined using Fourier transforms infrared spectroscopic (FT-IR) and scanning electron microscopic techniques respectively. FT-IR analyses indicated the lowering of hemi-cellulose and lignin contents by alkali treatment of the woven fabric. The scanning electron micrographs indicated the removal of hemicelluloses layer on the surface of the fabric by alkali treatment. The effect of alkali treatment of the natural fabric on the mechanical properties, chemical resistance, and interfacial bonding of the hybrid composites was examined.The mechanical properties of the woven fabric/glass fiber hybrid composites with surface modified natural fabric were found to be higher than those with untreated fabric. The fractographs indicated a better interfacial bonding between the woven fabric/glass fibres and the matrix, particularly when the alkali-treated natural fabrics were used in the hybrid composites. Furthermore, these hybrid composites showed resistance to acids, alkalis and various solvents and also possessed lower water absorption.The natural fabric/glass fibre hybrid composites have the properties which advise their relevance for application in the building and construction industries.
Abstract
High temperature tensile properties of 2D carbon-carbon composite made from high strength T700 carbon fibers were evaluated at different temperatures. Carbon-carbon composites were heat treated at different temperatures i.e., 750, 1000, 1500, 2000, 2500 °C and their tensile properties were measured ...
Read More
High temperature tensile properties of 2D carbon-carbon composite made from high strength T700 carbon fibers were evaluated at different temperatures. Carbon-carbon composites were heat treated at different temperatures i.e., 750, 1000, 1500, 2000, 2500 °C and their tensile properties were measured at room temperature and at different high temperatures. It is observed that, maximum value of tensile strength at room temperature is of composite heat treated at 1500 °C thereafter strength decreases with increasing processing temperature up to 2500 °C. The decreases in strength are related to degradation of fiber properties in composites and in-situ damage. On the other hand, tensile strength is higher at high temperature compared to room temperature. It increases progressively with increasing the test temperature up to 2000 °C. Thereafter, strength decreases and ultimate value of tensile strength is less than that of the room temperature value of 2500 °C heat treated composites. Increase in strength up to 1500 °C is due to the improvement in fiber-matrix interactions, matrix properties due to relaxation of thermally induced stresses during high temperature test. Above 1500 °C enhancement in tensile strength is due to the enhancement in strength of carbon fibers and due to the creep deformation. Decrease in strength at measurement temperature 2500 °C is due to the additional in-situ degradation of fiber properties during high temperature test. Copyright © 2011 VBRI press.