A constitutive model of nanocrystalline metals based on competing grain boundary and grain interior deformation mechanisms

In this work, a viscoplastic constitutive model for nanocrystalline metals is presented. The model is based on competing grain boundary and grain interior deformation mechanisms. In particular, inelastic deformations caused by grain boundary diffusion, grain boundary sliding and dislocation activities are considered. Effects of pressure on the grain boundary diffusion and sliding mechanisms are taken into account. Furthermore, the influence of grain size distribution on macroscopic response is studied. The model is shown to capture the fundamental mechanical characteristics of nanocrystalline metals. These include grain size dependence of the strength, i.e., both the traditional and the inverse Hall-Fetch effects, the tension-compression asymmetry and the enhanced rate sensitivity.


Investigation of the variations in microstructure and mechanical properties of dual-matrix ductile iron by Magnetic Barkhausen Noise analysis
Gür, Cemil Hakan; Erdogan, Mehmet (Informa UK Limited, 2008-01-01)
The variations in the microstructure and tensile properties of dual-matrix ductile irons have been investigated non-destructively by Magnetic Barkhausen Noise (MBN) method. Specimens have been intercritically austenitised at 795 degrees C and 815 degrees C for 20 minutes, and then oil-quenched to obtain different martensite volume fractions. Two specimens, namely as-cast and oil-quenched from 900 degrees C, were prepared for comparison purpose. To investigate the effect of tempering, some specimens were tem...
A study of phase stability and mechanical properties of hydroxylapatite-nanosize alpha-alumina composites
Evis, Zafer (Elsevier BV, 2007-04-01)
Hydroxylapatite (HA)-nanosize alumina composites were synthesized to study their phase stability and mechanical properties. To make these composites, nanosize alpha-Al2O3 powder was used because of its better sinterability and densification as compared to nanosize gamma-Al2O3. The composites were air sintered without pressure and hot pressed in vacuum at 1100 degrees C and 1200 degrees C. In the composites, HA decomposed to tricalcium phosphate faster after the air sintering than hot pressing. Moreover, hex...
A variational multiscale constitutive model for nanocrystalline materials
Gürses, Ercan (Elsevier BV, 2011-03-01)
This paper presents a variational multi-scale constitutive model in the finite deformation regime capable of capturing the mechanical behavior of nanocrystalline (nc) fcc metals. The nc-material is modeled as a two-phase material consisting of a grain interior phase and a grain boundary effected zone (GBAZ). A rate-independent isotropic porous plasticity model is employed to describe the GBAZ, whereas a crystal-plasticity model which accounts for the transition from partial dislocation to full dislocation m...
Observation of in situ enhanced crystallization, negative resistance effect and photosensitivity in Tl2InGaSe4 crystals
Qasrawi, A. F.; Irshaid, Tahani M. A.; Hasanlı, Nızamı (Elsevier BV, 2021-02-01)
In this work, we report the properties of Tl2InGaSe4 crystals as multifunctional material. Namely, Tl2InGaSe4 crystals are grown by the modified Bridgman method using mixtures of TlInSe2 (50%) and TlGaSe2 (50%) single crystals. The enhanced crystallization and structural stabilities are monitored by the X-ray diffraction technique during the in situ heating and cooling cycles. The structural analyses on the Tl2InGaSe4 crystals revealed domination of both of the monoclinic and tetragonal phases in the crysta...
A novel, simple, organic free preparation and characterization of water dispersible photoluminescent Cu2O nanocubes
Zahmakiran, Mehmet; Özkar, Saim; Kodaira, Tetsuya; Shiomi, Toru (Elsevier BV, 2009-02-15)
A novel method was developed for the organic and polymer free preparation of Cu2O nanocubes. Water-dispersible Cu2O nanocubes were prepared at room temperature by using a simple two steps procedure: the reduction of copper(II) sulfate by sodium borohydride generates the copper(O) nanoclusters stabilized by hydrogenphosphate towards the aggregation in aqueous solution. The hydrogen phosphate stabilized copper(0) nanoclusters initially formed are slowly oxidized by dissolved oxygen forming the Cu2O nanocubes ...
Citation Formats
E. Gürses, “A constitutive model of nanocrystalline metals based on competing grain boundary and grain interior deformation mechanisms,” MATERIALS LETTERS, pp. 3391–3395, 2011, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/36287.