Effect of dislocation density and aging on the yield stress of Al-Cu-Mg-Mn alloys

1973 ◽  
Vol 5 (8) ◽  
pp. 956-959
Author(s):  
Yu. M. Vainblat ◽  
L. B. Ber ◽  
S. S. Khayurov
Keyword(s):  
Dislocation Density ◽  
Yield Stress

The plasticity and cleavage of polycrystalline beryllium I. Yield and flow stresses

1980 ◽  
Vol 370 (1740) ◽  
pp. 17-27 ◽  
Keyword(s):  
Grain Size ◽  
Flow Stress ◽  
Dislocation Density ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Dislocation Motion ◽  
Orientation Factor ◽  
High Rigidity ◽  
Rigidity Modulus

The dependence of the yield and flow stresses of vacuum-cast and extruded polycrystalline beryllium on the grain size, d, is studied over 20-400 °C. Both follow the standard d -1/2 relationship. The Taylor orientation factor in the deformation of the poly crystal is ca. 4.3. The marked temperature dependence of the yield stress between 20 and 200 °C arises primarily from the intragranular resistance to dislocation motion, in particular on prismatic planes. The variation of the flow stress with d1/2 increases progressively with strain and this is attributed to the effect of grain size on the dislocation density at a given strain; the increase is particularly marked for beryllium because of its high rigidity modulus.

Effect of Optimization of Shot Peening Parameters on Surface Integrity of NAK80

2010 ◽  
Vol 426-427 ◽  
pp. 537-539 ◽  
Author(s):  
Hong Miao ◽  
Dun Wen Zuo ◽  
Hong Feng Wang ◽  
X.W. Sha
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Crack Initiation ◽  
Yield Stress ◽  
Surface Integrity ◽  
Shot Peening ◽  
Experimental Result ◽  
Near Surface ◽  
Crystal Block

Shot peening is known to improve the fatigue performance of materials. The improvement in fatigue is that plastic deformation in the surface increases hardness, yield stress and microstrain of thinning Crystal block and dislocation density, and formed advantaged compress residual stress that are introduced into the near-surface of the components and which hinder crack initiation and growth. But over peening effect is produced when shot peening strengthening goes beyond a certain limit, which was adverse to improve surface quality. This paper adopted the optimization of the critical peening parameters to avoid appearing over peening effect. The experimental result showed that arc high value of optimal shot peening was 0.40mm.

Dislocations and Plasticity in Silicon Crystals by 3-D Mesoscopic Simulations

1998 ◽  
Vol 538 ◽  
Author(s):  
L.P. Kubin ◽  
A. Moulin ◽  
P. Pirouz
Keyword(s):  
Dislocation Density ◽  
Yield Stress ◽  
Low Temperatures ◽  
Mechanical Twinning ◽  
Mesoscopic Simulation ◽  
Brittle To Ductile Transition ◽  
Silicon Crystals ◽  
Partial Dislocations ◽  
Yield Point Phenomenon ◽  
Dislocation Sources

AbstractSeveral problems related to the dynamics of dislocation sources and the plasticity of silicon crystals are investigated with the help of a mesoscopic simulation. The questions successively examined are the dynamics of a source of perfect dislocations and the conditions under which perfect or partial dislocations are emitted by a source. This leads to a discussion of the initial steps of the model proposed by Pirouz for mechanical twinning and, further, to the suggestion that a relation may exist between several transitions experimentally observed at low temperatures in elemental or compound semi-conductors: a change in the slope of the yield stress vs. temperature curves, a brittle-to-ductile transition and a change in the nature of the mobile dislocations. Finally, simulations are presented of the yield point phenomenon that is a well-known feature of Si and Ge crystals. The results are discussed in terms of evolutionary laws for the total dislocation density during straining.

scholarly journals Prediction of Magnetic Properties of a Plastically Deformed Steel and One Way to Measure its Plastic Deformation

2020 ◽  
Vol 20 (2) ◽  
pp. 5-13
Author(s):  
M.J. Sablik
Keyword(s):  
Plastic Deformation ◽  
Magnetic Properties ◽  
Dislocation Density ◽  
Plastic Strain ◽  
Yield Stress ◽  
Magnetic Materials ◽  
Power Law ◽  
Phenomenological Model ◽  
Magnetic Hysteresis ◽  
Hysteresis Loss

AbstractIn this paper, we use a phenomenological model based on the Jiles-Atherton-Sablik model of stress affecting the magnetic hysteresis of magnetic materials as modified when stress goes past the yield stress We use this to show that (1) the model produces sharp shearing of hysteresis curves, as seen experimentally and that (2) it also produces a step in the hysteresis loss at small residual plastic strain. We also find that the step in the hysteresis loss can be fitted to a power law, and find that the power law can be fitted by the power m=0.270, different from the mechanical Ludwik Law exponent, and reasonably close to the experimental 0.333 and 0.202. We will also suggest a method of measuring how plastically deformed the material is by suggesting how the dislocation density can be measured.

Deformation Behavior of Ultrafine Grained Iron

2006 ◽  
Vol 503-504 ◽  
pp. 317-322 ◽  
Author(s):  
Setsuo Takaki ◽  
Kenji Kawasaki ◽  
Y. Futamura ◽  
Toshihiro Tsuchiyama
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Yield Stress ◽  
Grain Refinement ◽  
Work Hardening ◽  
Coarse Grained ◽  
Deformation Condition ◽  
Initial Yield Stress ◽  
Ultrafine Grained ◽  
Dislocation Strengthening

Work hardening behavior and microstructure development during deformation by cold rolling were investigated in iron with different grain size. Grain refinement makes the introduction of dislocation easier. For instance, under the same deformation condition (5% reduction in thickness), dislocation density is the order of 1014m-2 in a coarse grained material (mean grain size; 20μm), while it reaches 7×1015m-2 in an ultrafine grained material (0.25μm). It is well known that the yield stress of metals is enlarged with an increase in dislocation density on the basis of the Bailey-Hirsch relationship. However, it should be noted that the ultrafine grained material never undergoes usual work hardening although the dislocation density is surely enhanced to around the order of 1016m-2: 0.2% proof stress is almost constant at 1.4 ~ 1.5GPa regardless of the amount of deformation. The dislocation density of 1016m-2 is thought to be the limit value which can be achieved by cold working of iron and the yield stress of iron with this dislocation density (ρ) is estimated at 1.1GPa from the Bailey-Hirsch relationship; σd [Pa] = 0.1×109 + 10 ρ1/2. On the other hand, yield stress of iron is enhanced by grain refinement on the basis of the Hall-Petch relationship; σgb [Pa] = 0.1×109 + 0.6×109 d-1/2 as to the grain size d [μm]. This equation indicates that the grain size of 0.35 μm gives the same yield stress as that estimated for the limit of dislocation strengthening (1.1GPa). As a result, it was concluded that work hardening can not take place in ultrafine grained iron with the grain size less than 0.35 μm because dislocation strengthening can not exceed the initial yield stress obtained by grain refinement strengthening.

Solid-state recycling for machined chips of iron by hot extrusion and annealing

2004 ◽  
Vol 19 (5) ◽  
pp. 1524-1530 ◽  
Author(s):  
Yasumasa Chino ◽  
Hajime Iwasaki ◽  
Mamoru Mabuchi
Keyword(s):  
Solid State ◽  
Dislocation Density ◽  
Yield Stress ◽  
Grain Refinement ◽  
Pure Iron ◽  
Room Temperature ◽  
Hot Extrusion ◽  
Low Energy ◽  
High Dislocation Density ◽  
High Ductility

Solid-state recycling for machined chips of pure iron by hot extrusion at 823 K and annealing at 1073–1273 K was carried out. The as-extruded solid recycled specimen without annealing was fractured prior to yielding at room temperature. However, high ductility was recovered by annealing at 1073–1273 K. This is because the oxides at the interface of the machined chips dispersed in grain by annealing. The annealed solid recycled specimens showed higher yield stress than the annealed virgin extruded specimens. Grain refinement for the solid recycled specimens was enhanced by the high dislocation density in the machined chips, resulting in higher strength in the recycled specimens. Thus, the solid-state recycling is a low energy upgrade recycle process.

Dependence of the Yield and Fatigue Strength of the Thread Rolled Mild Steel on Dislocation Density

2006 ◽  
Vol 129 (1) ◽  
pp. 216-222 ◽  
Author(s):  
J. Aghazadeh Mohandesi ◽  
Mohammad A. Rafiee ◽  
O. Maffi ◽  
P. Saffarzadeh
Keyword(s):  
Fatigue Strength ◽  
Dislocation Density ◽  
Yield Stress ◽  
High Speed ◽  
Machining Process ◽  
Fine Layered Structure ◽  
Thread Rolling ◽  
Substructure Formation ◽  
Full Annealing ◽  
Steel Bolts

Dependence of the yield and fatigue strength of steel bolts with composition in accordance to AISI 1035 manufactured by thread rolling and machining process on dislocation density were investigated. The results indicate that the fatigue strength of the rolled bolts are 55% higher than the machined bolts and by full annealing at 850°C, it reduced to the extent of machined specimen. Partial annealing of the thread rolled bolts at 680°C caused a reduction of fatigue strength by approximately 61% due to reduction in the dislocation density. Fatigue strength was improved by deformation rate (i.e., rolling speed), which is also due to the increasing dislocation density. Yield stress of the studied specimens followed the same pattern as fatigue strength. Considering the obtained results from the low and high speed, partial and full annealed thread rolled specimens, yield stress of the thread rolled bolts has been modeled based on the dislocation density. The obtained results from the model are in good agreement with the experimental results. The contribution to fatigue strength by thread rolling stems from the strain hardening effect which would facilitate the formation of compressive residual stress near the surface layer. The strengthening may be attributed to increasing dislocation density in the ferrite phase (i.e., substructure formation), in addition to the formation of a fine layered structure consisting of elongated pearlite colonies and ferrite grains.

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