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High-temperature deformation and structural restoration of a nanostructured Al alloy [electronic resource]
, Article Journal of Scripta Materialia (Pergamon) ; June 2012, Volume 66, Issue 11, Pages 911–914 ; Simchi, A. (Abdolreza) ; Kim, H. S ; Sharif University of Technology
Abstract
We studied the flow stress and microstructural changes of nanostructured Al-6063 alloy produced by mechanical alloying at various temperatures and strain rates. The analysis of flow curves was performed by a constitutive equation, and the stress exponent and activation energy were determined as functions of strain. The deformation mechanisms were elaborated through microstructural observations by electron backscattering diffraction and transmission electron microscopy. Coarsening of the subgrains and grain growth upon deformation was monitored and related to the Zener–Hollomon parameter
High temperature mechanical properties of triple phase steels
, Article Materials Letters ; Volume 61, Issue 4-5 , 2007 , Pages 1023-1026 ; 0167577X (ISSN) ; Sharif University of Technology
2007
Abstract
A 0.15% C-1.2% Si-1.7% Mn steel was intercritically annealed at 780 °C for 5 min and then isothermally held at 400 °C for 4 min followed by oil quenching to room temperature and the annealed microstructure consist of 75% ferrite, 15% bainite and 10% retained austenite was produced. Samples of this steel with triple phase structure were tensile tested at temperature range of 25-450 °C. Stress-strain curves showed serration flow at temperature range of 120-400 °C and smooth flow at the other temperatures. All of the stress-strain curves showed discontinuous yielding at all testing temperatures. Both yield and ultimate tensile strength decreased with increasing temperature, but there exists a...
High temperature mechanical properties of dual phase steels
, Article Materials Letters ; Volume 59, Issue 16 , 2005 , Pages 2070-2074 ; 0167577X (ISSN) ; Sharif University of Technology
2005
Abstract
Dual phase steels with different martensite volume fraction and morphology were tensile tested at temperature range of 25-550 °C. Stress-strain curves of all steels showed serration flow at temperature range of 250-450 °C and smooth flow at the other temperatures. Both yield and ultimate tensile strengths increased with increasing testing temperature up to about 450 °C and then decreased at higher temperatures. At a given temperature, yield stress, tensile strength, and work hardening increased with increasing volume fraction of martensite. Similar behavior was observed by changing martensite morphology from network to fibrous martensite. The change in mechanical properties was related to...
A Study on Hot Deformation and Kinetics of Softening in an Aluminum Alloy (AA5052)
, M.Sc. Thesis Sharif University of Technology ; Serajzadeh, Siamak (Supervisor)
Abstract
In this work, the deformation behavior of an Aluminium-Magnesium alloy i.e. AA5052, in different temperature ranges was studied experimentally and theoretically. For this purpose, uniaxial tensile tests were carried out in the temperature range of 25°C to 450°C and under strain rates of 0.001 "s-1" to 0.05 "s-1" . Also, the occurrence of dynamic strain aging and dynamic softening mechanisms of the alloy were taken into account. It was observed that the dynamic strain aging occurred in the temperature range of 25°C to 125°C while the corresponding activation energy was defined as 46.2 kJ/mol which is close to migration of Mg atoms in aluminum. At hot deformation region, different softening...
High-temperature deformation and structural restoration of a nanostructured Al alloy
, Article Scripta Materialia ; Volume 66, Issue 11 , 2012 , Pages 911-914 ; 13596462 (ISSN) ; Simchi, A ; Kim, H. S ; Sharif University of Technology
2012
Abstract
We studied the flow stress and microstructural changes of nanostructured Al-6063 alloy produced by mechanical alloying at various temperatures and strain rates. The analysis of flow curves was performed by a constitutive equation, and the stress exponent and activation energy were determined as functions of strain. The deformation mechanisms were elaborated through microstructural observations by electron backscattering diffraction and transmission electron microscopy. Coarsening of the subgrains and grain growth upon deformation was monitored and related to the Zener-Hollomon parameter
The influence of heat treatment and hot deformation conditions on γ′ precipitate dissolution of Nimonic 115 superalloy
, Article International Journal of Advanced Manufacturing Technology ; Volume 45, Issue 9-10 , 2009 , Pages 841-850 ; 02683768 (ISSN) ; Sadeghi, M. H ; Akbarzadeh, A ; Cheraghzadeh, M ; Sharif University of Technology
Abstract
In precipitation hardenable materials, it is desirable to determine the precipitate dissolution temperature for homogenizing the microstructure by controlling the size and distribution of the precipitates. In this research, the influence of various heat treatment and hot deformation conditions on the kinetics of γ ′ dissolution and its morphological evolution in Nimonic 115 was studied. In addition, hot deformation behavior of the material was investigated using hot compression experiments at varying temperature (between 1,050°C and 1,175°C) and strain rates (between 0.01 and 1 s-1) up to a true strain of 0.8. The values obtained for the solvus temperature of γ ′ precipitates by two methods...
High temperature deformation and processing map of a NiTi intermetallic alloy
, Article Intermetallics ; Volume 19, Issue 10 , October , 2011 , Pages 1399-1404 ; 09669795 (ISSN) ; Aboutalebi, M ; Kheirandish, S ; Karimi Taheri, A ; Abbasi, S. M ; Sharif University of Technology
2011
Abstract
The deformation behavior of a 49.8 Ni-50.2 Ti (at pct) alloy was investigated using the hot compression test in the temperature range of 700 °C-1100 °C, and strain rate of 0.001 s-1 to 1 s-1. The hot tensile test of the alloy was also considered to assist explaining the related deformation mechanism within the same temperature range and the strain rate of 0.1 s-1. The processing map of the alloy was developed to evaluate the efficiency of hot deformation and to identify the instability regions of the flow. The peak efficiency of 24-28% was achieved at temperature range of 900 °C-1000 °C, and strain rates higher than 0.01 s -1 in the processing map. The hot ductility and the deformation...
Creep behavior of hot extruded Al-Al2O3 nanocomposite powder
, Article Materials Science and Engineering A ; Volume 527, Issue 10-11 , 2010 , Pages 2567-2571 ; 09215093 (ISSN) ; Simchi, A ; Seyed Reihani, S. M ; Sharif University of Technology
2010
Abstract
A commercial gas-atomized aluminum powder was mechanically milled in a planetary ball mill under an argon atmosphere for 12 h to produce alumina dispersion strengthened aluminum powder. Transmission electron microscopy (TEM) revealed that about 2 vol.% alumina particles with an average size of 100 nm were distributed in the aluminum matrix. The nanocomposite powder was canned in an aluminum container, vacuum de-gassed, and hot extruded at 723 K at an extrusion ratio of 16:1. The creep behavior of the extruded billet in the direction of extrusion was examined at a constant applied load ranging from 10 to 40 MPa at temperatures of 648, 673 and 723 K. A threshold creep-stress was noticed which...