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Benjamin T Britton - One of the best experts on this subject based on the ideXlab platform.
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dislocation density distribution at Slip Band grain boundary intersections
Acta Materialia, 2020Co-Authors: Yi Guo, Angus J Wilkinson, David M Collins, Edmund Tarleton, Felix Hofmann, Benjamin T BrittonAbstract:Abstract We study the mechanisms of Slip transfer at a grain boundary, in titanium, using Differential Aperture X-ray Laue Micro-diffraction (DAXM). This 3D characterisation tool enables measurement of the full (9-component) Nye lattice curvature tensor and calculation of the density of geometrically necessary dislocations (GNDs). We observe dislocation pile-ups at a grain boundary, as the neighbour grain prohibits easy passage for dislocation transmission. This incompatibility results in local micro-plasticity within the Slipping grain, near to where the Slip planes intersect the grain boundary, and we observe Bands of GNDs lying near the grain boundary. We observe that the distribution of GNDs can be significantly influenced by the formation of grain boundary ledges that serve as secondary dislocation sources. This observation highlights the non-continuum nature of polycrystal deformation and helps us understand the higher order complexity of grain boundary characteristics.
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stress fields and geometrically necessary dislocation density distributions near the head of a blocked Slip Band
Acta Materialia, 2012Co-Authors: Benjamin T Britton, Angus J WilkinsonAbstract:Abstract We have examined the interaction of a blocked Slip Band and a grain boundary in deformed titanium using high-resolution electron backscatter diffraction and atomic force microscopy. From these observations, we have deduced the active dislocation types and assessed the dislocation reactions involved within a selected grain. Dislocation sources have been activated on a prism Slip plane, producing a planar Slip Band and a pile-up of dislocations in a near screw alignment at the grain boundary. This pile-up has resulted in activation of plasticity in the neighbouring grain and left the boundary with a number of dislocations in a pile-up. Examination of the elastic stress state ahead of the pile-up reveals a characteristic “one over the square root of distance” dependence for the shear stress resolved on the active Slip plane. This observation validates a dislocation mechanics model given by Eshelby, Frank and Nabarro in 1951 and not previously directly tested, despite its importance in underpinning our understanding of grain size strengthening, fracture initiation, short fatigue crack propagation, fatigue crack initiation and many more phenomena. The analysis also provides a method to measure the resistance to Slip transfer of an individual grain boundary in a polycrystalline material. For the boundary and Slip systems analysed here a Hall–Petch coefficient of K = 0.41 MPa m ½ was determined.
Yi Guo - One of the best experts on this subject based on the ideXlab platform.
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dislocation density distribution at Slip Band grain boundary intersections
Acta Materialia, 2020Co-Authors: Yi Guo, Angus J Wilkinson, David M Collins, Edmund Tarleton, Felix Hofmann, Benjamin T BrittonAbstract:Abstract We study the mechanisms of Slip transfer at a grain boundary, in titanium, using Differential Aperture X-ray Laue Micro-diffraction (DAXM). This 3D characterisation tool enables measurement of the full (9-component) Nye lattice curvature tensor and calculation of the density of geometrically necessary dislocations (GNDs). We observe dislocation pile-ups at a grain boundary, as the neighbour grain prohibits easy passage for dislocation transmission. This incompatibility results in local micro-plasticity within the Slipping grain, near to where the Slip planes intersect the grain boundary, and we observe Bands of GNDs lying near the grain boundary. We observe that the distribution of GNDs can be significantly influenced by the formation of grain boundary ledges that serve as secondary dislocation sources. This observation highlights the non-continuum nature of polycrystal deformation and helps us understand the higher order complexity of grain boundary characteristics.
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Slip Band grain boundary interactions in commercial purity titanium
Acta Materialia, 2014Co-Authors: Yi Guo, Tb B. Britton, Aj J. WilkinsonAbstract:Abstract The interaction between Slip Bands and grain boundaries in commercial-purity titanium was examined using cross-correlation-based electron backscatter diffraction. At a low strain level, three types of interactions were observed: blocked Slip Band with stress concentration; Slip transfer; and blocked Slip Band with no stress concentration. The stress concentration induced by the blocked Slip Band was fitted with Eshelby’s theoretical model, from which a Hall–Petch coefficient was deduced. It was found that the Hall–Petch coefficient varies with the individual grain boundary. We investigated the geometric alignment between the Slip Band and various Slip systems to the neighbouring grain. Stress concentration can be induced by the blocked Slip Band if the Slip system is poorly aligned with 〈 a 〉 prismatic, pyramidal or basal Slip systems in the neighbouring grain. Transfer of Slip across the boundary occurs when there is good alignment on 〈 a 〉 prismatic or 〈 a 〉 pyramidal Slip systems. Other stress-relieving mechanisms are possible when the best alignment is not with the Slip system that has the lower critical resolved shear stress.
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Slip Band–grain boundary interactions in commercial-purity titanium
Acta Materialia, 2014Co-Authors: Yi Guo, Tb B. Britton, Aj J. WilkinsonAbstract:Abstract The interaction between Slip Bands and grain boundaries in commercial-purity titanium was examined using cross-correlation-based electron backscatter diffraction. At a low strain level, three types of interactions were observed: blocked Slip Band with stress concentration; Slip transfer; and blocked Slip Band with no stress concentration. The stress concentration induced by the blocked Slip Band was fitted with Eshelby’s theoretical model, from which a Hall–Petch coefficient was deduced. It was found that the Hall–Petch coefficient varies with the individual grain boundary. We investigated the geometric alignment between the Slip Band and various Slip systems to the neighbouring grain. Stress concentration can be induced by the blocked Slip Band if the Slip system is poorly aligned with 〈 a 〉 prismatic, pyramidal or basal Slip systems in the neighbouring grain. Transfer of Slip across the boundary occurs when there is good alignment on 〈 a 〉 prismatic or 〈 a 〉 pyramidal Slip systems. Other stress-relieving mechanisms are possible when the best alignment is not with the Slip system that has the lower critical resolved shear stress.
Angus J Wilkinson - One of the best experts on this subject based on the ideXlab platform.
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dislocation density distribution at Slip Band grain boundary intersections
Acta Materialia, 2020Co-Authors: Yi Guo, Angus J Wilkinson, David M Collins, Edmund Tarleton, Felix Hofmann, Benjamin T BrittonAbstract:Abstract We study the mechanisms of Slip transfer at a grain boundary, in titanium, using Differential Aperture X-ray Laue Micro-diffraction (DAXM). This 3D characterisation tool enables measurement of the full (9-component) Nye lattice curvature tensor and calculation of the density of geometrically necessary dislocations (GNDs). We observe dislocation pile-ups at a grain boundary, as the neighbour grain prohibits easy passage for dislocation transmission. This incompatibility results in local micro-plasticity within the Slipping grain, near to where the Slip planes intersect the grain boundary, and we observe Bands of GNDs lying near the grain boundary. We observe that the distribution of GNDs can be significantly influenced by the formation of grain boundary ledges that serve as secondary dislocation sources. This observation highlights the non-continuum nature of polycrystal deformation and helps us understand the higher order complexity of grain boundary characteristics.
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stress fields and geometrically necessary dislocation density distributions near the head of a blocked Slip Band
Acta Materialia, 2012Co-Authors: Benjamin T Britton, Angus J WilkinsonAbstract:Abstract We have examined the interaction of a blocked Slip Band and a grain boundary in deformed titanium using high-resolution electron backscatter diffraction and atomic force microscopy. From these observations, we have deduced the active dislocation types and assessed the dislocation reactions involved within a selected grain. Dislocation sources have been activated on a prism Slip plane, producing a planar Slip Band and a pile-up of dislocations in a near screw alignment at the grain boundary. This pile-up has resulted in activation of plasticity in the neighbouring grain and left the boundary with a number of dislocations in a pile-up. Examination of the elastic stress state ahead of the pile-up reveals a characteristic “one over the square root of distance” dependence for the shear stress resolved on the active Slip plane. This observation validates a dislocation mechanics model given by Eshelby, Frank and Nabarro in 1951 and not previously directly tested, despite its importance in underpinning our understanding of grain size strengthening, fracture initiation, short fatigue crack propagation, fatigue crack initiation and many more phenomena. The analysis also provides a method to measure the resistance to Slip transfer of an individual grain boundary in a polycrystalline material. For the boundary and Slip systems analysed here a Hall–Petch coefficient of K = 0.41 MPa m ½ was determined.
J C Girard - One of the best experts on this subject based on the ideXlab platform.
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on Slip Band features and crack initiation in fatigued 316l austenitic stainless steel part 1 analysis by electron back scattered diffraction and atomic force microscopy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2002Co-Authors: P Villechaise, Laurent Sabatier, J C GirardAbstract:Electron back-scattered diffraction (EBSD) and atomic force microscopy (AFM) have been used to study surface Slip features on 316L austenitic stainless steel polycrystals tested in the low cycle fatigue range. EBSD investigations allow activated Slip planes to be identified for each grain and the local inclination of these Slip planes to the surface to be calculated. AFM allows the height of steps induced at the surface along Slip Bands to be measured and the local morphology of extrusions to be characterized at a nanometer scale. In this study, both techniques are used on the same surface in order to combine crystallographic and topographic information. Based on the results, a schematic model of the Slip Band emergence is proposed.
D V Lychagin - One of the best experts on this subject based on the ideXlab platform.
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friction induced Slip Band relief of hadfield steel single crystal oriented for multiple Slip deformation
Wear, 2017Co-Authors: D V Lychagin, A V Filippov, O S Novitskaia, Y I Chumlyakov, E A Kolubaev, O V SizovaAbstract:Abstract Hadfield steel is characterized both by high wear-resistance and ability to strain hardening. Due to these properties Hadfield steel is widely used in various industrial applications. The present investigation is aimed at analyzing the deformational behavior of Hadfield steel single crystals with [10 7 1] and [ 3 4 2 ] compression and friction axis orientations, respectively. Consecutive experiments under constant loading conditions have demonstrated the deformation-induced relief development stages as well as succession of Slip system activation in the process. Both Slip Band step height and inter-Band space increased due to the development of the maximum stress concentration zone and distortions of the near-end zone. The sequence and direction of the shear in the analyzed systems are ascertained by analyzing the shear stress value and the deformation relief.