The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
R Z Valiev - One of the best experts on this subject based on the ideXlab platform.
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microstructure and properties of pure ti processed by ecap and cold Extrusion
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001Co-Authors: V V Stolyarov, Y T Zhu, Terry C Lowe, R Z ValievAbstract:Abstract Equal channel angular pressing (ECAP) has been used to refine the grain size of commercially pure (CP) Ti as well as other metals and alloys. CP-Ti is usually processed at about 400°C because it lacks sufficient ductility at lower temperatures. The warm processing temperature limits the capability of the ECAP technique in improving the strength of CP-Ti. We have employed cold Extrusion following warm ECAP to further refine the grains and improve the strength of CP-Ti. Ti billets were first processed for eight passes via ECAP route BC, with a clockwise rotation of 90° between adjacent passes. They were further processed by successive cold Extrusions to an accumulative reduction in cross-section area by 47 or 75%. This paper reports the surface quality, microstructures, microhardness, tensile properties, and thermal stability of these Ti billets processed by a combination of ECAP and cold Extrusion.
Sven Sangerlaub - One of the best experts on this subject based on the ideXlab platform.
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recycling of blends made of polypropylene and an iron based oxygen scavenger influence of multiple Extrusions on the polymer stability and the oxygen absorption capacity
Polymer Degradation and Stability, 2015Co-Authors: Daniel Schlemmer, Markus Lehner, Sven SangerlaubAbstract:Abstract An often used oxygen scavenger is a blend of iron powder and additives dispersed in a polymer carrier matrix. It is applied as an additive for separate layers of multilayer film structures which are produced by coExtrusion. Not much is known about the influence of multiple Extrusions, for example during recycling processes, of these materials on polymer properties, film properties and process stability. Therefore the aim of this study was to assess these issues. The focus was on polypropylene because it is a common blend partner for iron-based oxygen scavenger additives. Pure polypropylene and blends of polypropylene with approximately 20 wt.-% iron-based oxygen scavenger additive (SHELFPLUS ® O 2 2710) were extruded up to ten times at two temperature profiles (T1: 160–230 °C; T2: 210–300 °C). Polymer degradation was evaluated by different means of measurement: MFR, DSC, colorimetry, IR-spectroscopy and oxygen absorption. The results indicate that polypropylene and polypropylene with dispersed oxygen scavenger degrade by the impact of Extrusion which can be seen by increased MFR and crystallinity and color changes. Furthermore the iron particles did undergo changes regarding color and oxygen scavenging capacity. The absorption capacity at 23 °C was reduced by one third from 39 to 48 mg oxygen per one gram scavenger additive after one Extrusion to 26–35 mg oxygen per one gram scavenger additive after 9 and 10 Extrusion cycles, respectively. Overall the iron based oxygen scavenger has a lower impact on degradation than the temperature and the number of Extrusions.
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Recycling of blends made of polypropylene and an iron-based oxygen scavenger – Influence of multiple Extrusions on the polymer stability and the oxygen absorption capacity
Polymer Degradation and Stability, 2015Co-Authors: Markus Lehner, Daniel Schlemmer, Sven SangerlaubAbstract:Abstract An often used oxygen scavenger is a blend of iron powder and additives dispersed in a polymer carrier matrix. It is applied as an additive for separate layers of multilayer film structures which are produced by coExtrusion. Not much is known about the influence of multiple Extrusions, for example during recycling processes, of these materials on polymer properties, film properties and process stability. Therefore the aim of this study was to assess these issues. The focus was on polypropylene because it is a common blend partner for iron-based oxygen scavenger additives. Pure polypropylene and blends of polypropylene with approximately 20 wt.-% iron-based oxygen scavenger additive (SHELFPLUS ® O 2 2710) were extruded up to ten times at two temperature profiles (T1: 160–230 °C; T2: 210–300 °C). Polymer degradation was evaluated by different means of measurement: MFR, DSC, colorimetry, IR-spectroscopy and oxygen absorption. The results indicate that polypropylene and polypropylene with dispersed oxygen scavenger degrade by the impact of Extrusion which can be seen by increased MFR and crystallinity and color changes. Furthermore the iron particles did undergo changes regarding color and oxygen scavenging capacity. The absorption capacity at 23 °C was reduced by one third from 39 to 48 mg oxygen per one gram scavenger additive after one Extrusion to 26–35 mg oxygen per one gram scavenger additive after 9 and 10 Extrusion cycles, respectively. Overall the iron based oxygen scavenger has a lower impact on degradation than the temperature and the number of Extrusions.
G Zhang - One of the best experts on this subject based on the ideXlab platform.
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length scale controlled fatigue mechanisms in thin copper films
Acta Materialia, 2006Co-Authors: Patrick Wellner, Cynthia A. Volkert, Ruth Schwaiger, G Zhang, Eduard Arzt, O KraftAbstract:Systematic investigations of fatigue damage and dislocation structures in thin Cu films with different thicknesses (0.2–3.0 lm) and grain sizes (0.3–2.1 lm mean diameter) were carried out using focused ion beam microscopy and transmission electron microscopy. The morphologies of fatigue-induced Extrusions, cracks, and dislocation structures were studied and found to be controlled by film thickness and grain size. When either of these length scales is decreased below roughly 1 lm, the typical dislocation wall and cell structures found in fatigued coarse-grained bulk materials no longer develop and are replaced by individual dislocations. Similarly, the typical surface damage of fatigued bulk metals, such as Extrusions and cracks near Extrusions, is gradually suppressed and replaced by damage that is localized at interfaces, such as cracks, grooves, and voids along grain and twin boundaries. This gradual transition from damage characteristic of bulk metals to damage localized at interfaces is attributed to constraints on dislocation activity at submicrometer length scales. Based on the experimental results and a theoretical analysis of Extrusion formation, a mechanistic map of fatigue damage behavior is proposed that summarizes this length scale dependence.
V V Stolyarov - One of the best experts on this subject based on the ideXlab platform.
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microstructure and properties of pure ti processed by ecap and cold Extrusion
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001Co-Authors: V V Stolyarov, Y T Zhu, Terry C Lowe, R Z ValievAbstract:Abstract Equal channel angular pressing (ECAP) has been used to refine the grain size of commercially pure (CP) Ti as well as other metals and alloys. CP-Ti is usually processed at about 400°C because it lacks sufficient ductility at lower temperatures. The warm processing temperature limits the capability of the ECAP technique in improving the strength of CP-Ti. We have employed cold Extrusion following warm ECAP to further refine the grains and improve the strength of CP-Ti. Ti billets were first processed for eight passes via ECAP route BC, with a clockwise rotation of 90° between adjacent passes. They were further processed by successive cold Extrusions to an accumulative reduction in cross-section area by 47 or 75%. This paper reports the surface quality, microstructures, microhardness, tensile properties, and thermal stability of these Ti billets processed by a combination of ECAP and cold Extrusion.
O Kraft - One of the best experts on this subject based on the ideXlab platform.
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length scale controlled fatigue mechanisms in thin copper films
Acta Materialia, 2006Co-Authors: Patrick Wellner, Cynthia A. Volkert, Ruth Schwaiger, G Zhang, Eduard Arzt, O KraftAbstract:Systematic investigations of fatigue damage and dislocation structures in thin Cu films with different thicknesses (0.2–3.0 lm) and grain sizes (0.3–2.1 lm mean diameter) were carried out using focused ion beam microscopy and transmission electron microscopy. The morphologies of fatigue-induced Extrusions, cracks, and dislocation structures were studied and found to be controlled by film thickness and grain size. When either of these length scales is decreased below roughly 1 lm, the typical dislocation wall and cell structures found in fatigued coarse-grained bulk materials no longer develop and are replaced by individual dislocations. Similarly, the typical surface damage of fatigued bulk metals, such as Extrusions and cracks near Extrusions, is gradually suppressed and replaced by damage that is localized at interfaces, such as cracks, grooves, and voids along grain and twin boundaries. This gradual transition from damage characteristic of bulk metals to damage localized at interfaces is attributed to constraints on dislocation activity at submicrometer length scales. Based on the experimental results and a theoretical analysis of Extrusion formation, a mechanistic map of fatigue damage behavior is proposed that summarizes this length scale dependence.
