The Role of Plastic Flow by Dislocation Motion in the Sintering of Calcium Fluoride

1969 ◽  
pp. 375-391 ◽  
Author(s):  
A. R. Hingorany ◽  
F. V. Lenel ◽  
G. S. Ansell
Keyword(s):  
Plastic Flow ◽  
Calcium Fluoride ◽  
Dislocation Motion

scholarly journals From plastic flow to brittle fracture: Role of microscopic friction in amorphous solids

2019 ◽  
Vol 100 (1) ◽  
Author(s):  
Kamran Karimi ◽  
David Amitrano ◽  
Jérôme Weiss
Keyword(s):  
Brittle Fracture ◽  
Plastic Flow ◽  
Amorphous Solids

Distinct role of eutectic morphology on the plastic flow in cast Mg–3Ca alloy

2020 ◽  
Vol 791 ◽  
pp. 139633
Author(s):  
N.T.B.N. Koundinya ◽  
Ravi Sankar Kottada
Keyword(s):  
Plastic Flow ◽  
Eutectic Morphology ◽  
Distinct Role

Irradiation-Induced Grain Growth: Role of Dislocations

1989 ◽  
Vol 157 ◽  
Author(s):  
Charles W. Allen ◽  
Lynn E. Rehn
Keyword(s):  
Grain Growth ◽  
Point Defects ◽  
Ion Irradiation ◽  
Boundary Migration ◽  
Dislocation Motion ◽  
Boundary Structure ◽  
Thermal Growth ◽  
Growth Phenomenon

ABSTRACTExisting theories of irradiation-induced grain growth assume that growth occurs by the boundary migration mechanism commonly observed for thermal growth and that it is only the point defects generated si boundaries during the irradiation which are responsible for boundary migration. In contrast, in situ observations during ion irradiation of Au films at temperatures less than 20 K even have clearly demonstrated that growth occurs both by boundary migration and by grain coalescence. Here we present further evidence for the latter. Furthermore, the substantial defect cluster activity observed during irradiation suggests that dislocations play a significant role in the growth phenomenon. Here, we also demonstrate qualitatively that glide of such dislocations to or “through” a boundary can produce essentially the same effect on boundary position or structure that the original point defects would have had if they had migrated individually to or through the boundary. Via dislocation motion, point defects originating far from a boundary may induce boundary migration or boundary structure change, and hence, grain growth.

Role of Deformable Fine Spinel Particles in High-Strain-Rate Superplastic Flow of Tetragonal ZrO2

2004 ◽  
Vol 821 ◽  
Author(s):  
Koji Morita ◽  
Keijiro Hiraga ◽  
Byung-Nam Kim ◽  
Yoshio Sakka
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Flow Behavior ◽  
Grain Boundary Sliding ◽  
Dislocation Motion ◽  
Particle Dispersion ◽  
Stress Concentrations ◽  
Tensile Direction

AbstractThe role of MgAl2O4 spinel particle dispersion in high-strain-rate superplasticity (HSRS) of tetragonal ZrO2 was examined by characterizing microstructural changes during deformation. The dispersed spinel particles elongate with strain along tensile direction and the elongation tends to be pronounced with increasing strain rate. In the elongated spinel particles, intragranular dislocations lying along the elongated direction were observed, suggesting that the elongation relates to the dislocation motion. The flow behavior characterized by a stress exponent of ≈ 2.0 suggests that grain boundary sliding (GBS) is the predominant flow mechanism. The dislocation-induced plasticity in the spinel particles may assist the relaxation of stress concentrations exerted by GBS, leading to HSRS in tetragonal ZrO2.

scholarly journals Critical assessment of hydrogen effects on the slip transmission across grain boundaries in α -Fe

2016 ◽  
Vol 472 (2185) ◽  
pp. 20150617 ◽  
Author(s):  
I. Adlakha ◽  
K. N. Solanki
Keyword(s):  
Grain Boundaries ◽  
Intergranular Fracture ◽  
Energy Barrier ◽  
Strain Energy ◽  
Strengthening Mechanism ◽  
Dislocation Motion ◽  
Dislocation Network ◽  
Mode Transition ◽  
Slip Transmission

Grain boundaries (GBs) play a fundamental role in the strengthening mechanism of crystalline structures by acting as an impediment to dislocation motion. However, the presence of an aggressive environment such as hydrogen increases the susceptibility to intergranular fracture. Further, there is a lack of systematic investigations exploring the role of hydrogen on the dislocation–grain-boundary (DGB) interactions. Thus, in this work, the effect of hydrogen on the interactions between a screw dislocation and 〈111〉 tilt GBs in α -Fe were examined. Our simulations reveal that the outcome of the DGB interaction strongly depends on the underlying GB dislocation network. Further, there exists a strong correlation between the GB energy and the energy barrier for slip transmission. In other words, GBs with lower interfacial energy demonstrate a higher barrier for slip transmission. The introduction of hydrogen along the GB causes the energy barrier for slip transmission to increase consistently for all of the GBs examined. The energy balance for a crack initiation in the presence of hydrogen was examined with the help of our observations and previous findings. It was found that the presence of hydrogen increases the strain energy stored within the GB which could lead to a transgranular-to-intergranular fracture mode transition.

On the Cutting of Metals: A Mechanics Viewpoint

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Dinakar Sagapuram ◽  
Anirudh Udupa ◽  
Koushik Viswanathan ◽  
James B. Mann ◽  
Rachid M’Saoubi ◽  
...  
Keyword(s):  
Plastic Flow ◽  
Chip Formation ◽  
Metal Cutting ◽  
Large Strain ◽  
Shear Banding ◽  
Continuous Shear ◽  
Recent Developments ◽  
Flow Phenomena ◽  
The Stability

Abstract The mechanics of large-strain deformation in cutting of metals is discussed, primarily from viewpoint of recent developments in in situ analysis of plastic flow and microstructure characterization. It is shown that a broad range of deformation parameters can be accessed in chip formation—strains of 1–10, strain rates of 10–105/s, and temperatures up to 0.7Tm—and controlled. This range is far wider than achievable by any other single-stage, severe plastic deformation (SPD) process. The resulting extreme deformation conditions produce a rich variety of microstructures in the chip. Four principal types of chip formation—continuous, shear-localized, segmented, and mushroom-type—as elucidated first by Nakayama (1974, “The Formation of ‘Saw-Toothed Chip’ in Metal Cutting,” Proceedings of International Conference on Production Engineering, Tokyo, pp. 572–577) are utilized to emphasize the diverse plastic flow phenomena, especially unsteady deformation modes that prevail in cutting. These chip types are intimately connected with the underlying flow, each arising from a distinct mode and triggered by an instability phenomenon. The role of plastic flow instabilities such as shear banding, buckling, and fracture in mediating unsteady flow modes is expounded, along with consequences of the flow modes and chip types for the cutting. Sinuous flow is shown to be the reason why gummy (highly strain-hardening) metals, although relatively soft, are so difficult to cut. Synthesizing the various observations, a hypothesis is put forth that it is the stability of flow modes that determines the mechanics of cutting. This leads to a flow-stability phase diagram that could provide a framework for predicting chip types and process attributes.

scholarly journals The role of quench rate on the plastic flow and fracture of three aluminium alloys with different grain structure and texture

2020 ◽  
Vol 150 ◽  
pp. 103257 ◽  
Author(s):  
Bjørn Håkon Frodal ◽  
Emil Christiansen ◽  
Ole Runar Myhr ◽  
Odd Sture Hopperstad
Keyword(s):  
Plastic Flow ◽  
Aluminium Alloys ◽  
Grain Structure ◽  
Quench Rate
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