scholarly journals Grain Refinement Assisted by Deformation Enhanced Precipitates through Thermomechanical Treatment of AA7055 Al Alloy

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 594 ◽  
Author(s):  
Jinrong Zuo ◽  
Longgang Hou ◽  
Xuedao Shu ◽  
Wenfei Peng ◽  
Anmin Yin ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Grain Refinement ◽  
Thermomechanical Treatment ◽  
Drag Force ◽  
High Strength ◽  
Good Alternative ◽  
Al Alloy ◽  
Intermediate Annealing ◽  
Static Recovery ◽  
Dislocation Cells

Fine-grained sheets of AA7055 Al alloy were produced by an improved double-stage rolling thermomechanical treatment (DRTMT) assisted by deformation-enhanced precipitates (DEPs). The DRTMT composed of a low temperature pre-deformation, an intermediate annealing, and a final hot rolling exhibited significantly superior tensile ductility to the conventional rolling thermomechanical treated alloy (CRTMT). Numerous fine spherical DEPs appeared after the pre-deformation. Those DEPs could exert a strong drag force on the migration of boundaries and dislocations. Dislocation cells were formed due to the drag force and dynamic recovery. These dislocation cells become polygon sub-grains by static recovery during the subsequent intermediate annealing. After the final hot deformation, with further deformation and rising temperature, low angle grain boundaries gradually stabilized and transferred to high angle grain boundaries. Due to the transformation, fine equiaxed grains were formed after DRTMT. The DRTMT alloys display superior elongation to the CRTMT alloy while maintaining high strength for grain refinement. Thus, DRTMT would be a good alternative to manufacture different heat-treatable Al alloys with fine grains efficiently.

The mechanism of grain refinement and plasticity enhancement by an improved thermomechanical treatment of 7055 Al alloy

2017 ◽  
Vol 702 ◽  
pp. 42-52 ◽  
Author(s):  
Jinrong Zuo ◽  
Longgang Hou ◽  
Jintao Shi ◽  
Hua Cui ◽  
Linzhong Zhuang ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Thermomechanical Treatment ◽  
Al Alloy

Improvement of Mechanical Properties and Corrosion Resistance by Deformation Induced Precipitation in Al-Zn-Mg-Cu Alloy

2017 ◽  
Vol 898 ◽  
pp. 179-190 ◽  
Author(s):  
Jin Rong Zuo ◽  
Long Gang Hou ◽  
Jin Tao Shi ◽  
Hua Cui ◽  
Lin Zhong Zhuang ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Thermomechanical Treatment ◽  
High Strength ◽  
Alloy Sheet ◽  
Rolling Temperature ◽  
Al Alloy ◽  
Deformation Degree ◽  
Dynamic Aging ◽  
Final Rolling Temperature ◽  
Final Rolling

A final thermomechanical treatment (FTMT) including peak aging and subsequent dynamic aging was proposed to prepare 7055 Al alloy sheets. The optimization was based on nine well-planned orthogonal experiments. Three main processing conditions in the thermomechanical treatment for obtaining the optimum synthetic properties of 7055 (i.e. preheating temperature, final rolling temperature and deformation degree) were investigated. It was shown that the final rolling temperature is the most important factor among the three parameters, and the optimum properties (yield strength: 651 MPa, ultimate tensile strength: 660 MPa) of 7055 Al alloy sheet can be gained with preheating at 140oC and 40% deformation at 170oC. With dynamic aging, grain boundary precipitates became discontinuous without much coarsening of matrix precipitates, while they were continuously distributed after T6 aging. The present optimal FTMT process can improve the intergranular / exfoliation corrosion resistance without sacrificing the strength compared to T6 tempering. The present FTMT process as a good alternative can produce high-strength Al alloy sheets with high strength and good corrosion resistance efficiently and economically.

Influence of ECAP Routes on the Microstructure and Mechanical Properties of Hot Extruded 3003 Al Alloy

2007 ◽  
Vol 124-126 ◽  
pp. 1397-1400 ◽  
Author(s):  
Byoung Soo Lee ◽  
Hoon Cho
Keyword(s):  
Mechanical Properties ◽  
Grain Refinement ◽  
Hot Extrusion ◽  
High Strength ◽  
Al Alloy ◽  
Deformation Structure ◽  
Ecap Processing ◽  
Fine Grained ◽  
Strain Process ◽  
Equiaxed Grains

The microstructures and mechanical properties of unidirectional deformation structured Al alloy during ECAP with various deformation routes were investigated. In order to fabricate unidirectional deformation structure for Al alloy, hot extrusion was carried out. It was found that the deformation route A in ECAP routes is the dominant route for the grain refinement and strengthening. In deformation route A, the high strength ultra-fine grained Al alloy with a grain size of ~ 200 nm was obtained due to the accumulation of consecutive strain process. In contrast, the strength of ECAP’ed Al alloy produced via deformation route C was greatly increased after one pass because the grains were strained and cancelled each pass. By contrast, the equiaxed grains were obtained in deformation route BC because the sample was rotated 90 O in the same sense in each pass. The deformation route BC was superior to the deformation route C because the deformation route BC was more favorable than the deformation route C in the accumulation of consecutive strain. It is also found that unidirectional deformation structured Al alloy via hot extrusion shows similar grain refinement tendency with equiaxed structured Al alloy during ECAP processing.

Equal Channel Angular Pressing of Al Alloy AA2219

2009 ◽  
Vol 67 ◽  
pp. 53-58
Author(s):  
V. Anil Kumar ◽  
M.K. Karthikeyan ◽  
Rohit Kumar Gupta ◽  
P. Ramkumar ◽  
P.P. Sinha
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Equal Channel Angular Pressing ◽  
High Strength ◽  
Dark Field ◽  
Grain Structure ◽  
Al Alloy ◽  
Angular Pressing

Severe plastic deformation processes (SPD) are gaining importance as advanced materials processing techniques and hold immense potential in obtaining ultra fine-grained high strength materials. Among the SPD techniques, Equal channel angular pressing (ECAP) has its own merits to produce materials with ultra fine grains in bulk with better mechanical properties. The material deforms with high level of plastic strain inside the channel resulting in grain refinement of the output material with improvement in mechanical properties. A very viable die configuration was conceptualized and die was made with 1200 channel angle. Processing of 25 mm dia. of Al alloy AA2219 at room temperature was successfully carried out and grain refinement was observed. The mechanism of grain refinement has been studied using optical and transmission electron microscopy (TEM). It was observed that low energy dislocation structure (LEDS) forms concurrently with sub-grain structure due to dislocation rearrangements, which provide stability to the evolving sub-grain structure. Dislocation mobility is hindered by the presence of precipitates and / or intermetallic dispersoids present in the matrix and results in presence of dislocations in grain interiors. The pile up of dislocations at intermetallic dispersoids was confirmed from the dark field TEM micrographs. Present paper describes the experimental procedure and followed to attain severe plastic deformation through ECAP. Increase in hardness as well as refinement in the grain size after 5-passes have been discussed in light of extensive optical and TEM. The mechanisms of grain refinement to achieve nano-grained structure and strengthening accrued from the grain refinement through ECAP has been discussed.

Improved thermo-mechanical processing for effective grain refinement of high-strength AA 7050 Al alloy

2015 ◽  
Vol 626 ◽  
pp. 86-93 ◽  
Author(s):  
Wangtu Huo ◽  
Longgang Hou ◽  
Yujing Lang ◽  
Hua Cui ◽  
Linzhong Zhuang ◽  
...  
Keyword(s):  
Grain Refinement ◽  
High Strength ◽  
Al Alloy ◽  
Mechanical Processing

scholarly journals Effect of Deformation on Precipitation and the Microstructure Evolution during Multistep Thermomechanical Processing of Al-Zn-Mg-Cu Alloy

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1409
Author(s):  
Jinrong Zuo ◽  
Longgang Hou ◽  
Xuedao Shu ◽  
Wenfei Peng ◽  
Anmin Yin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Electron Microscope ◽  
Grain Boundaries ◽  
Grain Refinement ◽  
Hot Rolling ◽  
Hot Deformation ◽  
Rolling Process ◽  
Intermediate Annealing ◽  
Short Period

In order to obtain fine grained structure efficiently, a new multi-step rolling process (MSR: pre-deformation + intermediate annealing + hot deformation) was applied in Al-Zn-Mg-Cu plates. Conventional hot rolling (CHR) was also carried out as a contrast experiment. The evolution of microstructures and improvement of mechanical properties were analyzed by optical microscope, scanning electron microscope, transmission electron microscope, X-ray diffractometer, and tensile tests. The results show that the MSR process can obtain finer longitudinal grain size and better mechanical properties than CHR, which can be explained as follows: spheroidization of precipitates wrapped by high density dislocations could be promoted by increased pre-deformation; numerous ordered substructures were formed during short-period intermediate annealing at high temperature; in the subsequent hot rolling process, the retained spherical precipitates pinned dislocations and boundaries. With the increase of accumulated strain, low angle grain boundaries gradually transformed into high angle grain boundaries, leading to grain refinement. With the increased pre-deformation (MSR1 20 + 60%, MSR2 40 + 40%, MSR3 60 + 20%), the effect of grain refinement and plasticity improvement gradually weakened. The optimum thermomechanical process (MSR1 solid solution + pre-deformation (300 °C/20%) + intermediate annealing (430 °C/5 min) + hot deformation (400 °C/60%)) was obtained, which can increase elongation by ~25% compared with the CHR process, while maintaining similar high strength for reduced longitudinal grain size.

Precipitation on Low Angle Boundaries in Al-Zn-Mg

1980 ◽  
Vol 38 ◽  
pp. 374-375
Author(s):  
Diane M. Vanderwalker
Keyword(s):  
Grain Boundaries ◽  
High Strength ◽  
Boundary Structure ◽  
Aircraft Industry ◽  
Precipitate Free Zone ◽  
High Angle ◽  
Adjacent Region ◽  
Free Zone ◽  
Widespread Interest

There is a widespread interest in understanding the properties of Al-base alloys so that progress can be made toward extending their present applications in the aircraft industry. Al-Zn-Mg is precipitation hardened to gain its high strength; however, during aging the formation of heterogeneous precipitates on the grain boundaries creates a precipitate-free zone in the adjacent region. Since high angle grain boundaries are not easily characterized, it is difficult to establish a relationship between the precipitate and the boundary structure. Therefore, this study involves precipitation on low angle grain boundaries where the boundary and the precipitate can be fully analyzed.

Mechanical Properties and Aging Behavior of Ultrafine Grained Al-Ag Alloy Fabricated by Accumulative Roll-Bonding

2014 ◽  
Vol 794-796 ◽  
pp. 851-856
Author(s):  
Tadashiege Nagae ◽  
Nobuhiro Tsuji ◽  
Daisuke Terada
Keyword(s):  
Mechanical Properties ◽  
Grain Refinement ◽  
Accumulative Roll Bonding ◽  
Precipitation Hardening ◽  
Tensile Elongation ◽  
Solution Treatment ◽  
High Strength ◽  
Subsequent Aging ◽  
Roll Bonding ◽  
Ultrafine Grained

Accumulative roll-bonding (ARB) process is one of the severe plastic deformation processes for fabricating ultrafine grained materials that exhibit high strength. In aluminum alloys, aging heat treatment has been an important process for hardening materials. In order to achieve good mechanical properties through the combination of grain refinement hardening and precipitation hardening, an Al-4.2wt%Ag binary alloy was used in the present study. After a solution treatment at 550°C for 1.5hr, the alloy was severely deformed by the ARB process at room temperature (RT) up to 6 cycles (equivalent strain of 4.8). The specimens ARB-processed by various cycles (various strains) were subsequently aged at 100, 150, 200, 250°C, and RT. The hardness of the solution treated (ST) specimen increased by aging. On the other hand, hardness of the ARB processed specimen decreased after aging at high temperatures such as 250°C. This was probably due to coarsening of precipitates or/and matrix grains. The specimen aged at lower temperature showed higher hardness. The maximum harnesses achieved by aging for the ST specimen, the specimens ARB processed by 2 cycles, 4 cycles and 6 cycles were 55HV, 71HV, 69HV and 65HV, respectively. By tensile tests it was shown that the strength increased by the ARB process though the elongation decreased significantly. However, it was found that the tensile elongation of the ARB processed specimens was improved by aging without sacrificing the strength. The results suggest that the Al-Ag alloy having large elongation as well as high strength can be realized by the combination of the ARB process for grain refinement and the subsequent aging for precipitation hardening.

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