Ultrafine Grain Evolution in a Cu-Cr-Zr Alloy during Warm Multidirectional Forging

2014 ◽  
Vol 783-786 ◽  
pp. 2683-2688
Author(s):  
Iaroslava Shakhova ◽  
Andrey Belyakov ◽  
Alexander P. Zhilyaev ◽  
Rustam Kaibyshev
Keyword(s):  
Flow Behavior ◽  
Total Strain ◽  
Ultrafine Grain ◽  
Second Phase ◽  
Steady State Flow ◽  
Multidirectional Forging ◽  
Grain Sizes ◽  
Solution Treated ◽  
Ultrafine Grained ◽  
Zr Alloy

The microstructure evolution and the deformation behavior of a Cu-0.3%Cr-0.5%Zr alloy subjected to multidirectional forging at a temperature of 673 K under a strain rate of about 10-3 s-1 were studied. Following a rapid increase in the flow stress during straining to about 1, the strain hardening gradually decreases, leading to a steady-state flow behavior at total strain above 2. The multidirectional forging led to the development of ultrafine grained microstructures with mean grain sizes of 0.9 μm and 0.64 μm in the solution treated and aged samples, respectively. The presence of second phase precipitates promoted the grain refinement. After processing to a total strain of 4, the fractions of ultrafine grains (D < 2 μm) comprised 0.36 and 0.59 in the solution treated and aged samples, respectively.

Extending Creep and Superplasticity to Materials with Submicrometer Grain Sizes

2007 ◽  
Vol 345-346 ◽  
pp. 539-544
Author(s):  
Megumi Kawasaki ◽  
Cheng Xu ◽  
Z. Horita ◽  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
Aluminum Alloys ◽  
Severe Plastic Deformation ◽  
Flow Behavior ◽  
Ultrafine Grain ◽  
Grain Sizes ◽  
Large Samples ◽  
Angular Pressing ◽  
Recent Advances ◽  
Ultrafine Grained

The mechanisms of creep and superplasticity occurring in conventional large-grained materials are now understood reasonably well. However, very recent advances in the processing of theoretically-dense metals with submicrometer grain sizes have provided the opportunity to extend the understanding of flow behavior to include materials where the grains are exceptionally small. Using processing through the application of severe plastic deformation, as in procedures such as equal-channel angular pressing, it is now feasible to fabricate relatively large samples having ultrafine grain sizes in the submicrometer or nanometer range. This paper examines these recent advances and gives examples of the flow behavior in ultrafine-grained aluminum alloys.

Microstructure and Aging Behavior of Al-0.2wt%Zr Alloy Heavily Deformed by ARB Process

2008 ◽  
Vol 584-586 ◽  
pp. 728-733 ◽  
Author(s):  
Takatoshi Sato ◽  
Daisuke Terada ◽  
Nobuhiro Tsuji
Keyword(s):  
Grain Size ◽  
Microstructural Evolution ◽  
Coarse Grain ◽  
Aging Behavior ◽  
Roll Bonding ◽  
Solution Treated ◽  
Ultrafine Grained ◽  
Mean Grain Size ◽  
Treated State ◽  
Zr Alloy

An Al-0.2wt%Zr alloy was severely deformed up to a strain of 8.0 by accumulative roll bonding (ARB) process, started from the solution-treated state. The microstructural evolution during ARB and its aging behavior were investigated. With increasing the number of ARB cycles, Vickers hardness of the specimens increased and reached to a constant value. The microstructural evolution during the ARB could be understood in terms of grain subdivision. The ultrafine grained (UFG) materials whose mean grain size was 0.4 -m were obtained by 10-cycle ARB process. In aging of the ARB processed specimens at high temperatures above 673K, the UFG microstructures quickly coarsened. On the other hand, it was suggested that the precipitation behaviors of the ARB specimen at 623K were quite unique and completely different from those of the conventionally solution-treated material with coarse grain size.

Structure and Properties of CuCr0.6 Alloy after Severe Plastic Deformation

2017 ◽  
Vol 890 ◽  
pp. 327-330
Author(s):  
Kinga Rodak ◽  
Joanna Sobota ◽  
Wojciech Głuchowski
Keyword(s):  
Electrical Conductivity ◽  
Subgrain Boundary ◽  
Aging Treatment ◽  
Ultrafine Grain ◽  
Precipitation Process ◽  
Second Phase ◽  
High Mechanical Strength ◽  
Ultrafine Grained ◽  
Second Phase Particles ◽  
Cyclic Movement

This paper focuses on the effect of rolling with cyclic movement of rolls (RCMR) on microstructure refinement, mechanical properties and electrical conductivity of CuCr0.6 alloy after applying different heat treatments (quenching and aging). It was found that the presence of second phase particles obtained during aging treatment has a significant effect on the formation of ultrafine grain (UFG) structure during the RCMR processing. The presence of high dislocation density inside subgrains and presence microshear bands are the marked features of the microstructure after aging at 500°C/2h and RCMR deformation. Whereas after aging at 700°C/24h and RCMR processing, fine precipitates were effective in inhibiting the grain/subgrain boundary motion. The RCMR processed alloy after aging at 500°C/2h shows high mechanical strength attributed to the high density of coherent precipitates and ultrafine grained structure. The RCMR processing induces a significant reduction of the electrical conductivity for samples at quenching state but for samples at aging state electrical conductivity was restored thanks to precipitation process.

scholarly journals Unique transition of yielding mechanism and unexpected activation of deformation twinning in ultrafine grained Fe-31Mn-3Al-3Si alloy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yu Bai ◽  
Hiroki Kitamura ◽  
Si Gao ◽  
Yanzhong Tian ◽  
Nokeun Park ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Twip Steel ◽  
Deformation Twinning ◽  
Ultrafine Grain ◽  
Yield Drop ◽  
Grain Sizes ◽  
Deformation Twins ◽  
Ultrafine Grained ◽  
The Mean

AbstractTensile mechanical properties of fully recrystallized TWIP steel specimens having various grain sizes (d) ranging from 0.79 μm to 85.6 μm were investigated. It was confirmed that the UFG specimens having the mean grain sizes of 1.5 μm or smaller abnormally showed discontinuous yielding characterized by a clear yield-drop while the specimens having grain sizes larger than 2.4 μm showed normal continuous yielding. In-situ synchrotron radiation XRD showed dislocation density around yield-drop in the UFG specimen quickly increased. ECCI observations revealed the nucleation of deformation twins and stacking faults from grain boundaries in the UFG specimen around yielding. Although it had been conventionally reported that the grain refinement suppresses deformation twinning in FCC metals and alloys, the number density of deformation twins in the 0.79 μm grain-sized specimen was much higher than that in the specimens with grain sizes of 4.5 μm and 15.4 μm. The unusual change of yielding behavior from continuous to discontinuous manner by grain refinement could be understood on the basis of limited number of free dislocations in each ultrafine grain. The results indicated that the scarcity of free dislocations in the recrystallized UFG specimens changed the deformation and twinning mechanisms in the TWIP steel.

Developing High Strain Rate Superplasticity in Aluminum Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 2949-2954 ◽  
Author(s):  
Cheng Xu ◽  
Minoru Furukawa ◽  
Z. Horita ◽  
Terence G. Langdon
Keyword(s):  
Elevated Temperatures ◽  
High Strain ◽  
Superplastic Forming ◽  
Ultrafine Grain ◽  
Strain Rates ◽  
Cast Aluminum ◽  
Grain Sizes ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Materials Used

The conventional materials used in superplastic forming operations generally have grain sizes of ~2 µm or larger and they exhibit superplasticity at relatively low strain rates. Processing by equal-channel angular pressing (ECAP) produces materials having ultrafine-grain sizes, usually in the submicrometer range. If these ultrafine grains show reasonable stability at elevated temperatures, the alloys may exhibit a capability for achieving superplastic elongations at high strain rates. This paper examines the development of ultrafine-grained structures and superplastic ductilities in a spray-cast aluminum 7034 alloys through ECAP. The results show that ECAP is a very effective procedure for achieving grain refinement and superplasticity at rapid strain rates.

High Speed Deformation of Ultrafine Grained TWIP Steel

2007 ◽  
Vol 561-565 ◽  
pp. 107-110 ◽  
Author(s):  
Rintaro Ueji ◽  
Kenji Harada ◽  
Noriyuki Tsuchida ◽  
Kazutoshi Kunishige
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Twip Steel ◽  
Ultrafine Grain ◽  
Grain Sizes ◽  
Ultrafine Grain Size ◽  
Ultrafine Grained ◽  
Wide Range ◽  
Twip Steels ◽  
Large Work

Tensile properties of twinning induced plasticity (TWIP) steels (31%Mn-3%Al-3%Si-Fe) with various mean grain sizes ranging from ultrafine grain size (1.1μm) to conventional one (35.5μm) at a wide range of strain rates from 10-3sec-1 to 103sec-1 were studied. The ultrafine grained TWIP steel exhibits a large work hardening and keeps an adequate elongation at any strain rate. The strength held to the Hall-Petch relationship at each strain rate and the Hall-Petch slopes do not change largely.

Effects of Initial Microstructure and Deformation Method on Grain Refinement in a Cu-Cr-Zr Alloy

2016 ◽  
Vol 838-839 ◽  
pp. 308-313
Author(s):  
Iaroslava Shakhova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Refinement ◽  
Submicrocrystalline Structure ◽  
Ultrafine Grain ◽  
Large Strains ◽  
Second Phase ◽  
Deformation Method ◽  
Ultrafine Grains ◽  
Continuous Dynamic Recrystallization ◽  
Multidirectional Forging ◽  
Angular Pressing

The development of submicrocrystalline structure in a Cu-0.3wt.%Cr-0.5wt.%Zr during multidirectional forging (MDF) and equal channel angular pressing (ECAP) was investigated in comparison. A large number of strain-induced subboundaries with low-angle misorientations appeared at early deformation. The subsequent straining led to an increase in the misorientations of these subboundaries, resulting in the formation of submicrocrystalline structure at sufficiently large strains. The process of microstructural evolution can be considered as continuous dynamic recrystallization. MDF provided faster kinetics of new ultrafine grain formation as compared to ECAP. The fraction of ultrafine grains with a size below 2 μm comprised 0.59 or 0.23 after MDF or ECAP to a total strain of 4, respectively. The grain refinement kinetics could be accelerated by the presence of second phase precipitates. The fraction of ultrafine grains after MDF to a strain of 4 achieved 0.36 or 0.59 in the solution treated or aged samples, respectively.

Effect of Ageing on Strength and Ductility of Ultrafine Grained Al 6061 Alloy

2009 ◽  
Vol 633-634 ◽  
pp. 303-309 ◽  
Author(s):  
Sushanta Kumar Panigrahi ◽  
D. Devanand ◽  
R. Jayaganthan
Keyword(s):  
Processing Condition ◽  
Solution Treatment ◽  
Ultrafine Grain ◽  
Ageing Treatment ◽  
Al 6061 ◽  
Solution Treated ◽  
Grain Structures ◽  
Ultrafine Grained ◽  
Ultrafine Grained Microstructure ◽  
Strength And Ductility

An effect of ageing on mechanical properties of ultrafine grained Al 6061 alloys has been investigated in the present work. The solution treated bulk Al 6061 alloy was subjected to cryorolling to produce ultrafine grain structures and subsequently ageing treatment to improve its both strength and ductility. The hardness and tensile properties of solution treated, cryorolled, cryorolled and aged Al alloys were measured and explained by using their corresponding microstructural morphologies. The pre-cryorolled solid solution treatment combined with post-CR ageing treatment (1300C-30h) has been found to be the optimum processing condition to obtain the ultrafine grained microstructure with improved tensile strength (362MPa) and good tensile ductility (10.7%) in the Al 6061 alloy. The combined effect of precipitation hardening and recovery are responsible for the simultaneous improvement of both strength and ductility observed in the present work.

Low Temperature Superplasticity of Ti-6Al-4V Processed by Warm Multidirectional Forging

2012 ◽  
Vol 735 ◽  
pp. 253-258 ◽  
Author(s):  
Gennady A. Salishchev ◽  
Egor A. Kudryavtsev ◽  
Sergey V. Zherebtsov ◽  
S. Lee Semiatin
Keyword(s):  
Low Temperature ◽  
Strain Rate ◽  
Flow Behavior ◽  
Rate Sensitivity ◽  
Sensitivity Coefficient ◽  
Total Elongation ◽  
Temperature Deformation ◽  
Ultrafine Grain ◽  
Two Phase ◽  
Multidirectional Forging

Multidirectional forging has been developed to produce an ultrafine-grain (UFG) microstructure in the two-phase titanium alloy Ti-6Al-4V. A microstructure with a grain size of 135 nm was attained, enabling low-temperature superplasticity (LTSP) at 550°C. A total elongation of 1000% and strain-rate-sensitivity coefficient m=0.47 were obtained at the optimal strain rate of 2×10-4 s-1. Important features of the microstructure and superplastic behavior of the alloy are summarized in the present work. It is shown that microstructure evolution during low-temperature deformation plays a key role in superplastic flow behavior.

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