scholarly journals Effect of Rolling Speed on Microstructural and Microtextural Evolution of Nb Tubes during Caliber-Rolling Process

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 500 ◽  
Author(s):  
Jongbeom Lee ◽  
Haguk Jeong
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Ambient Temperature ◽  
Strain Rate ◽  
Internal Energy ◽  
Grain Refinement ◽  
Rolling Process ◽  
Fiber Texture ◽  
Rolling Speed ◽  
Low Energy

This study investigated the fabrication of Nb tubes via the caliber-rolling process at various rolling speeds from 1.4 m/min to 9.9 m/min at ambient temperature, and the effect of the caliber-rolling speed on the microstructural and microtextural evolution of the Nb tubes. The caliber-rolling process affected the grain refinement when the Nb tube had a higher fraction of low angle grain boundaries. However, the grain size was identical regardless of the rolling speed. The dislocation density of the Nb tubes increased with the caliber-rolling speed according to the Orowan equation. The reduction of intensity for the <111> fiber texture and the development of the <112> fiber texture with the increase of the strain rate are considered to have decreased the internal energy by increasing the fraction of the low-energy Σ3 boundaries.

Computation on continuous grain refinement in AA1050 aluminum during repetitive tube expansion and shrinking technique

2015 ◽  
Vol 232 (4) ◽  
pp. 307-318
Author(s):  
H Jafarzadeh ◽  
K Abrinia
Keyword(s):  
Finite Element Method ◽  
Plastic Deformation ◽  
Grain Size ◽  
Finite Element ◽  
Dislocation Density ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Half Cycle ◽  
Tube Expansion ◽  
Element Method

The microstructure evolution during recently developed severe plastic deformation method named repetitive tube expansion and shrinking of commercially pure AA1050 aluminum tubes has been studied in this paper. The behavior of the material under repetitive tube expansion and shrinking including grain size and dislocation density was simulated using the finite element method. The continuous dynamic recrystallization of AA1050 during severe plastic deformation was considered as the main grain refinement mechanism in micromechanical constitutive model. Also, the flow stress of material in macroscopic scale is related to microstructure quantities. This is in contrast to the previous approaches in finite element method simulations of severe plastic deformation methods where the microstructure parameters such as grain size were not considered at all. The grain size and dislocation density data were obtained during the simulation of the first and second half-cycles of repetitive tube expansion and shrinking, and good agreement with experimental data was observed. The finite element method simulated grain refinement behavior is consistent with the experimentally obtained results, where the rapid decrease of the grain size occurred during the first half-cycle and slowed down from the second half-cycle onwards. Calculations indicated a uniform distribution of grain size and dislocation density along the tube length but a non-uniform distribution along the tube thickness. The distribution characteristics of grain size, dislocation density, hardness, and effective plastic strain were consistent with each other.

Superplastic Behavior of a Cu-Cr-Zr Alloy Subjected to ECAP

2016 ◽  
Vol 838-839 ◽  
pp. 404-409
Author(s):  
Roman Mishnev ◽  
Iaroslava Shakhova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Strain Rate ◽  
Temperature Interval ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Superplastic Behavior ◽  
Average Grain Size ◽  
Gauge Section ◽  
Zr Alloy

A Cu-0.87%Cr-0.06%Zr alloy was subjected to equal channel angular pressing (ECAP) at a temperature of 400 °C up to a total strain of ~ 12. This processing produced ultra-fine grained (UFG) structure with an average grain size of 0.6 μm and an average dislocation density of ~4×1014 m-2. Tensile tests were carried out in the temperature interval 450 – 650 °C at strain rates ranging from 2.8´10-4 to 0.55 s-1. The alloy exhibits superplastic behavior in the temperature interval 550 – 600 °C at strain rate over 5.5´10-3 s-1. The highest elongation-to-failure of ~300% was obtained at a temperature of 575 °C and a strain rate of 2.8´10-3 s-1 with the corresponding strain rate sensitivity of 0.32. It was shown the superplastic flow at the optimum conditions leads to limited grain growth in the gauge section. The grain size increases from 0.6 μm to 0.87 μm after testing, while dislocation density decreases insignificantly to ~1014 m-2.

Significance of High Rate Superplasticity in Metallic Materials

1990 ◽  
Vol 196 ◽  
Author(s):  
Norio Furushiro ◽  
Shigenori Hori
Keyword(s):  
Grain Size ◽  
High Strain Rate ◽  
Strain Rate ◽  
Grain Refinement ◽  
Fine Particles ◽  
High Strain ◽  
High Rate ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Al Alloy

ABSTRACTIt has been expected that “High rate superplastic materials” will be developed for industrial applications. The Dorntype equation for high temperature deformation suggests that strain rate can be increased if the grain size is decreased. This means that grain refinement can effectively establish high strain rate superplastic materials.It is well known that a high degree of grain size refinement will result from the addition of zirconium to Al-base alloys. Powder-metallurgical processing with rapidly solidified powders is also available for the improvement of superplasticity by both the refinement of the solidified structure and the maintenance of the stable fine structure of a 7475 Al alloy during recrystallization and deformation. Therefore. P/M 7475 Al alloys containing Zr up to 0.9 wt% were selected as candidate specimens. The objective of the present paper includes the clarification of the role and the effective amount of Zr to obtain high strain rate superplastic materials. As a result, the addition of 0.3%Zr or more is effective in grain refinement of the P/M 7475 Al alloy. However, alloys containing 0.7 and 0.9 wt%Zr only show superplasticity at 793K. The optimum strain rate is shifted to a higher range with increasing Zr. The alloy of 7475 Al-0.9%Zr shows the maximum elongation of 900% at the remarkably high strain rate of 3.3×10−1 s−1.The deformation mechanism of such high stain rate superplasticity will be discussed briefly, by considering the effect of the fine particles of Zr on superplastic behavior.

Microstructure and Mechanical Properties of Extruded Mg-Al-Ca Based Alloys

2005 ◽  
Vol 488-489 ◽  
pp. 275-278 ◽  
Author(s):  
Rong Shi Chen ◽  
Jean Jacques Blandin ◽  
Michel Suéry ◽  
En Hou Han
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elevated Temperature ◽  
Yield Strength ◽  
Ambient Temperature ◽  
Grain Refinement ◽  
Tensile Tests ◽  
Az91 Alloy ◽  
Microstructure And Mechanical Properties ◽  
Ca Addition

Mechanical properties and microstructure of extruded AZ91(-Ca) alloys have been studied in this paper. The results showed that Ca has no significant effect on reducing grain size of the extruded AZ91 alloy. The ambient temperature tensile tests showed that the ultimate and yield strength of extruded AZ91 alloy decreased by addition of Ca. At elevated temperature, Ca addition improves the yield strength of both AZ91 alloy. The variations in microstructure and mechanical properties of the AZ91 alloy are also discussed in terms of the effects of Ca on grain refinement and formation of constituent phases.

Dislocation Density-Based Grain Refinement Modeling of Orthogonal Cutting of Titanium

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Hongtao Ding ◽  
Yung C. Shin
Keyword(s):  
Grain Size ◽  
Finite Element ◽  
Dislocation Density ◽  
Mechanical Behavior ◽  
Grain Refinement ◽  
Orthogonal Cutting ◽  
Cutting Process ◽  
Plasticity Model ◽  
Numerical Work ◽  
Cp Ti

Recently, orthogonal cutting has been exploited as a means for producing ultrafine grained (UFG) and nanocrystalline microstructures for various metal materials, such as aluminum alloys, copper, stainless steel, titanium and nickel-based super alloys, etc. However, no predictive, analytical or numerical work has ever been presented to quantitatively predict the change of grain sizes during plane-strain orthogonal cutting. In this paper, a dislocation density-based material plasticity model is adapted for modeling the grain size refinement mechanism during orthogonal cutting by means of a finite element based numerical framework. A coupled Eulerian–Lagrangian (CEL) finite element model embedded with the dislocation density subroutine is developed to model the severe plastic deformation and grain refinement during a steady-state cutting process. The orthogonal cutting tests of a commercially pure titanium (CP Ti) material are simulated in order to assess the validity of the numerical solution through comparison with experiments. The dislocation density-based material plasticity model is calibrated to reproduce the observed material constitutive mechanical behavior of CP Ti under various strains, strain rates, and temperatures in the cutting process. It is shown that the developed model captures the essential features of the material mechanical behavior and predicts a grain size of 100–160 nm in the chips of CP Ti at a cutting speed of 10 mm/s.

Dynamic Deformation Behavior of ECAPed AZ31 Magnesium Alloy

2014 ◽  
Vol 566 ◽  
pp. 104-109
Author(s):  
Hai Tao Hu ◽  
Feng Zhao ◽  
Ying Gang Miao ◽  
Tao Suo ◽  
Qiong Deng ◽  
...  
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Hardening ◽  
Grain Refinement ◽  
Rate Sensitivity ◽  
Dynamic Mechanical Properties ◽  
Angular Pressing ◽  
Fine Grain ◽  
Split Hopkinson ◽  
Dynamic Deformation Behavior

Equal channel angular pressing (ECAP) has been widely used for grain refinement in many alloys. In this article, the major emphasis was on the effect of grain size, temperature and strain rate on dynamic behavior of ECAPed AZ31. The dynamic mechanical properties of 6 pass and 8 pass ECAPed AZ31 were tested by split hopkinson pressing bar (SHPB) at wide temperatures range. At dynamic loading conditions, the ECAPed AZ31 shows strong strain hardening properties. The strain hardening rates decrease due to more slip systems’ opening with the increase of temperature. With the grain refinement, the fine-grain size and temperature show strong effect on the strain rate sensitivity.

Grain Evolution Character of Discal Parts by Roll Forming

2013 ◽  
Vol 749 ◽  
pp. 328-336
Author(s):  
Quan Lin Jin
Keyword(s):  
Numerical Simulation ◽  
Grain Size ◽  
Titanium Alloy ◽  
Aluminum Alloy ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Grain Refinement ◽  
Grain Growth ◽  
Roll Forming ◽  
Alloy 6061

A study on grain evolution character of discal parts roll forming was carried out by means of experiment and numerical simulation. The discal part material is aluminum alloy 6061 and titanium alloy TC4. The roll forming temperature is 480-500 and 930-1020 for aluminum alloy 6061 and titanium alloy TC4, respectively. A digital double-sided roll forming machine was used for roll forming experiment of discal parts. The high frequency induction heating was used for disk heating, where the deformation zone is in the state of constant temperature. A numerical simulation of roll forming of the 6061 aluminum alloy disk was carried out. The simulated results include macroscopic deformation and various grain size evolution variables. The dynamic recrystallization, the dynamic and static grain growth were considered in the numerical simulation. The experimental and simulated results showed that there may appear not only the grain refinement due to dynamic recrystallization but also dynamic and static grain growth. It is different that from discal parts integrally forging there are the largest deformation, the highest strain rate and the best recrystallization and grain refinement in the zones contacted with the roll tools. In the zones far from the rollers, the strain rate is very low and average grain size increases until once again contact to the rollers and start new grain refinement.

Grain Refinement during Superplastic Deformation of Coarse-Grained Al-Mg-Cu Alloys

2006 ◽  
Vol 509 ◽  
pp. 75-80 ◽  
Author(s):  
M.I. Cruz-Palacios ◽  
D. Hernández-Silva ◽  
L.A. Barrales-Mora ◽  
M.A. García-Bernal
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Grain Refinement ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Mg Alloy ◽  
Coarse Grained ◽  
Dislocation Creep ◽  
Rolled Plate ◽  
Strain Rates

In the present study the superplastic behavior of Al-6%Mg–0.5%Cu and Al–8%Mg– 0.5%Cu in a coarse grain size condition has been studied. The alloys are melted in an electrical furnace under argon atmosphere. The ingots (25 mm thick) are homogenized at 400 °C during 72 h and then rolled at 430 °C to a thickness of 5 mm. The mean grain size after rolling is 55 µm for the 6%Mg alloy and 61 µm for the 8%Mg alloy. Tensile test specimens are machined from the rolled plate in the rolling direction. Strain-rate-change tests at temperatures between 300 and 450 °C and strain rates between 1x10-4 and 1x10-1 s-1 are carried out to determine the strain rate sensitivity of the flow stress. Finally, elongation to failure tests are conducted at temperatures and strain rates where the alloys show a high strain rate sensitivity. Elongations higher than 390 % are obtained for the 8%Mg alloy. It is observed that the grip regions of the deformed samples show coarser grains than the regions near to the fracture surface. This means that grain refinement takes place during deformation, suggesting that the principal deformation mechanism is dislocation creep.

scholarly journals Dislocation Density-Based Grain Refinement Modeling of Orthogonal Cutting of Commercially Pure Titanium

2011 ◽  
Author(s):  
Hongtao Ding ◽  
Yung C. Shin
Keyword(s):  
Grain Size ◽  
Finite Element ◽  
Dislocation Density ◽  
Mechanical Behavior ◽  
Grain Refinement ◽  
Orthogonal Cutting ◽  
Pure Titanium ◽  
Commercially Pure Titanium ◽  
Commercially Pure ◽  
Cp Ti

Recently, machining has been exploited as a means for producing ultra-fine grained (UFG) and nanocrystalline microstructures for various metal materials, such as aluminum alloys, copper, stainless steel, titanium and nickel-based super alloys, etc. However, no predictive, analytical or numerical work has ever been presented to quantitatively predict the change of grain sizes during machining. In this paper, a dislocation density-based viscoplastic model is adapted for modeling the grain size refinement mechanism during machining by means of a finite element based numerical framework. A novel Coupled Eulerian-Lagrangian (CEL) finite element model embedded with the dislocation density subroutine is developed to model the severe plastic deformation and grain refinement during a steady-state cutting process. The orthogonal cutting tests of a commercially pure titanium (CP Ti) material are simulated in order to assess the validity of the numerical solution through comparison with experiments. The dislocation density-based material model is calibrated to reproduce the observed material constitutive mechanical behavior of CP Ti under various strains, strain rates and temperatures in the cutting process. It is shown that the developed model captures the essential features of the material mechanical behavior and predicts a grain size of 100–160 nm in the chips of CP Ti at a cutting speed of 10 mm/s.

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