The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Stavros K Kourkoulis - One of the best experts on this subject based on the ideXlab platform.
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effect of ageing on precipitation kinetics tensile and work Hardening behavior of al cu mg 2024 alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Nikolaos D Alexopoulos, Zaneta Velonaki, Constantinos I Stergiou, Stavros K KourkoulisAbstract:Abstract The effect of artificial ageing conditions on precipitation kinetics, tensile and work Hardening Mechanical behavior of aluminum alloy 2024 was investigated. Tensile specimens were artificially aged in three different temperatures and for various times so as to bring the material in all possible ageing conditions. These included under-ageing (UA), peak-ageing (PA) and over-ageing (OA) and then the specimens were tensile tested. Yield stress was found to increase up to the peak-ageing condition with a simultaneously decrease in elongation at fracture due to the precipitation of the S -type particles. It was confirmed that precipitation kinetics of this alloy is in between the diffusivity rate of solute Cu and Mg atoms in the aluminum matrix. Peak yield stress was found to be absolutely dependent on the iso-thermal ageing temperature and it was experimentally noticed that a 6 MPa yield stress drop exists per increasing ageing temperature by 10 °C. At the OA condition, non-uniform elongation attains values exceeding 40% of total elongation, and therefore the damage tolerance capability of the material at this ageing condition is further reduced. Work Hardening Stage I dealing with pile-up of the dislocation debris of dipoles is almost double in PA when compared with the respective in UA condition. Duration of Stage II increases up to 40% of uniform elongation within the PA condition, where the precipitation transition of coherent S′′ to semi-coherent S′ type takes place. Stage II is essentially decreased in the OA condition to approximate 30% of uniform elongation, while dislocation cross slipping (Stage III) exceeds 50% of uniform elongation in the OA condition. Duration of Stages II and III for different artificial ageing conditions have a similar trend with yield stress and elongation at fracture values, respectively, thus giving proof that work Hardening stages are artificially aged sensitive.
Nikolaos D Alexopoulos - One of the best experts on this subject based on the ideXlab platform.
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effect of ageing on precipitation kinetics tensile and work Hardening behavior of al cu mg 2024 alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Nikolaos D Alexopoulos, Zaneta Velonaki, Constantinos I Stergiou, Stavros K KourkoulisAbstract:Abstract The effect of artificial ageing conditions on precipitation kinetics, tensile and work Hardening Mechanical behavior of aluminum alloy 2024 was investigated. Tensile specimens were artificially aged in three different temperatures and for various times so as to bring the material in all possible ageing conditions. These included under-ageing (UA), peak-ageing (PA) and over-ageing (OA) and then the specimens were tensile tested. Yield stress was found to increase up to the peak-ageing condition with a simultaneously decrease in elongation at fracture due to the precipitation of the S -type particles. It was confirmed that precipitation kinetics of this alloy is in between the diffusivity rate of solute Cu and Mg atoms in the aluminum matrix. Peak yield stress was found to be absolutely dependent on the iso-thermal ageing temperature and it was experimentally noticed that a 6 MPa yield stress drop exists per increasing ageing temperature by 10 °C. At the OA condition, non-uniform elongation attains values exceeding 40% of total elongation, and therefore the damage tolerance capability of the material at this ageing condition is further reduced. Work Hardening Stage I dealing with pile-up of the dislocation debris of dipoles is almost double in PA when compared with the respective in UA condition. Duration of Stage II increases up to 40% of uniform elongation within the PA condition, where the precipitation transition of coherent S′′ to semi-coherent S′ type takes place. Stage II is essentially decreased in the OA condition to approximate 30% of uniform elongation, while dislocation cross slipping (Stage III) exceeds 50% of uniform elongation in the OA condition. Duration of Stages II and III for different artificial ageing conditions have a similar trend with yield stress and elongation at fracture values, respectively, thus giving proof that work Hardening stages are artificially aged sensitive.
Z Zhuang - One of the best experts on this subject based on the ideXlab platform.
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atypical three stage Hardening Mechanical behavior of cu single crystal micropillars
Scripta Materialia, 2009Co-Authors: Z ZhuangAbstract:Three-dimensional discrete dislocation dynamics simulations have been used to study the stress–strain response of Cu single-crystal micropillars containing initial dislocation networks. When such networks are loaded, we find that the stress–strain curve can be divided into three distinct stages: a linear elastic stage, a normal strain Hardening stage and a “dislocation starvation Hardening” stage accompanying a rather high stress level. Finally, a perfect dislocation-free pillar is obtained in our simulations.
Nadia Passerini - One of the best experts on this subject based on the ideXlab platform.
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Modulation of Alendronate release from a calcium phosphate bone cement: An in vitro osteoblast-osteoclast co-culture study.
International Journal of Pharmaceutics, 2018Co-Authors: Luisa Stella Dolci, Silvia Panzavolta, Paola Torricelli, Beatrice Albertini, Laura Sicuro, Milena Fini, Adriana Bigi, Nadia PasseriniAbstract:Abstract In this study, we loaded a biomimetic calcium phosphate bone cement (CPC) with relatively high amounts of a bisphosphonate through the use of Solid Lipid Microparticles (MPs) and investigated bone cells response to the composite cements. 10, 20 and 30% w/w of Alendronate (AL) were successfully introduced into microparticles of Cutina HR and Precirol, which were prepared by means of spray-congealing technique. Addition of AL-loaded MPs to the cement composition provoked a lengthening of the setting and of the Hardening processes. However, setting times were still in a range useful for clinical applications, except for the cements at the highest Alendronate content. The composite cements displayed a sustained drug release over time. Cements with the best performances in terms of setting, Hardening, Mechanical properties and drug release were submitted to in vitro tests using a co-culture model of osteoblast and osteoclast. The results showed that the use of MPs to enrich the cement composition with Alendronate provides materials able to inhibit osteoclast viability and activity, while promoting osteoblast viability and earlier differentiation, indicating that the MPs-cements are good delivery systems for bisphosphonates.
Constantinos I Stergiou - One of the best experts on this subject based on the ideXlab platform.
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effect of ageing on precipitation kinetics tensile and work Hardening behavior of al cu mg 2024 alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Nikolaos D Alexopoulos, Zaneta Velonaki, Constantinos I Stergiou, Stavros K KourkoulisAbstract:Abstract The effect of artificial ageing conditions on precipitation kinetics, tensile and work Hardening Mechanical behavior of aluminum alloy 2024 was investigated. Tensile specimens were artificially aged in three different temperatures and for various times so as to bring the material in all possible ageing conditions. These included under-ageing (UA), peak-ageing (PA) and over-ageing (OA) and then the specimens were tensile tested. Yield stress was found to increase up to the peak-ageing condition with a simultaneously decrease in elongation at fracture due to the precipitation of the S -type particles. It was confirmed that precipitation kinetics of this alloy is in between the diffusivity rate of solute Cu and Mg atoms in the aluminum matrix. Peak yield stress was found to be absolutely dependent on the iso-thermal ageing temperature and it was experimentally noticed that a 6 MPa yield stress drop exists per increasing ageing temperature by 10 °C. At the OA condition, non-uniform elongation attains values exceeding 40% of total elongation, and therefore the damage tolerance capability of the material at this ageing condition is further reduced. Work Hardening Stage I dealing with pile-up of the dislocation debris of dipoles is almost double in PA when compared with the respective in UA condition. Duration of Stage II increases up to 40% of uniform elongation within the PA condition, where the precipitation transition of coherent S′′ to semi-coherent S′ type takes place. Stage II is essentially decreased in the OA condition to approximate 30% of uniform elongation, while dislocation cross slipping (Stage III) exceeds 50% of uniform elongation in the OA condition. Duration of Stages II and III for different artificial ageing conditions have a similar trend with yield stress and elongation at fracture values, respectively, thus giving proof that work Hardening stages are artificially aged sensitive.
