In the present work, the effect of grain boundary misorientation, deformation temperature and AlFeMnSi-phase on fatigue behavior of 6082 Al has been investigated. The 6082 Al alloy has been subjected to cryorolling followed by warm rolling at 100 °C–250 °C. The fatigue test of the processed alloy has been performed at stress ratio (R) of zero with different stress amplitude of 25, 50, 60, 70, 80, 90, and 110 MPa. The deformed alloy and fracture surface was characterized by using XRD, DSC, SEM and EDS to elucidate the role of AlFeMnSi-phase and Mg2Si-precipitates on fatigue life of the alloy. Cryorolling followed by Warm rolling (CR + WR) 6082 Al alloy rolled at 100 °C temperature showed higher dislocation density compared to other processed sample. The small size of AlFeMnSi-phase and Mg2Si-precipitates, high dislocation density and low angle grain boundaries had improved the fatigue life of 6082 Al alloy as observed in the present work. © 2017 Elsevier Inc.

Rengaswamy Jayaganthan

Department of Engineering Design

Deformation

Fatigue of materials

Fatigue testing

Grain boundaries

Rolling

6082 AL ALLOYS

Cryo-rolling

Deformation temperatures

Dislocation densities

Grain boundary misorientation

High dislocation density

Low angle grain boundaries

WARM-ROLLING

Aluminum

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

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IIT Madras

Materials Characterization

In this paper, room temperature forging (RTF, 25 °C) and warm forging (WF, 200 °C) of Al-Mg-Si alloy were performed, for strengthening the 6082 Al alloy at low applied strain. Overall WF-AlMgSi alloy forged just after 2 cycles (1.26 true strain) exhibits maximum hardness, tensile strength, J-integral value, and plastic strain in all investigated samples. This is due to: (i) the formation of ultrafine grain (UFG) of size 411 nm, (ii) the formation of stress free dynamic recrystallized (DRX) grains, and (iii) the complete precipitation of β"-phase. The UFG increased the hardness and yield strength (YS) according to the conventional Hall-Petch effect, and the β"-phase increased the hardness and the YS by providing the obstacle to the movement of mobile dislocations. The stress free DRX grains accommodate a large number of mobile dislocations, which further enhances the plastic strain. The UFG, the DRX grains, and the β"-phase effect, all combined together further enhance the J-integral value. The effects of RTF, WF and strains on the emergence of various forms of shear bands were also discussed in this paper. Softening effect on both RTF and WF-AlMgSi alloy after processing beyond 2 cycles is due to factors such as saturation of strengthening through Hall-Petch effect and coarsening of β"-phase in the RTF-AlMgSi alloy and β'-phase in the WF-AlMgSi alloy, respectively. © 2019

Al 6082 alloy strengthening through low strain multi-axial forging

Tensile properties, microstructural evolution and fracture toughness of Al 2014 alloy subjected to cryorolling followed by warm rolling (CR + WR) have been investigated in the present study. The solution-treated (ST) Al 2014 alloy is cryorolled followed by warm rolling process at different temperatures (110, 170 and 210 °C). The mechanical properties and microstructural features of deformed and undeformed Al 2014 alloys were characterised by optical microscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The CR + WR samples at 170 °C showed an improved hardness (179 HV), tensile (UTS 499 MPa, YS 457 MPa) and fracture toughness (KQ = 37.49 MPa m, Kee = 37.39 MPa m and J integral = 33.25 kJ/mm2) with respect to ST alloy as measured from the tensile and fracture toughness test. The improved mechanical properties of CR + WR alloy are attributed to grain boundary strengthening, combined recovery and recrystallisation, precipitation hardening and dynamic ageing effect during the deformation. The precipitation of metastable spherical phase Al2Cu was responsible for the improved tensile and fracture properties of fine-grained Al 2014 alloy observed in the present work. © 2018, The Chinese Society for Metals and Springer-Verlag GmbH Germany, part of Springer Nature.

Fulltext

Acta Metallurgica Sinica (English Letters)

Mechanical Properties and Microstructural Evolution of Bulk UFG Al 2014 Alloy Processed Through Cryorolling and Warm Rolling

The main objective of the present study was to investigate the effect of Mg/Si precipitates on the hot-compression response of Al-Mg-Si alloy and further inspect the influence of compression temperatures and Mg/Si precipitates on microstructural changes. The processing maps were drawn using the dynamic materials model approach. To validate the processing maps, metallurgical factors of different regions of processing map were investigated using differential scanning calorimetry (DSC) and electron back-scattered diffraction. The influence of strain rate on the flow stresses of Al-Mg-Si alloy is not consistent with the traditional results after compression from 100 to 250 °C, due to the strain ageing produced by the Mg/Si precipitates. The DSC study reveals that no Mg/Si precipitate evolved during the compression test after compressing beyond 250 °C. The processing maps (drawn at 0.1 true strain to 0.6 true strain) and metallurgical factors (high-angle grain boundaries or dynamic recrystallized grains) indicated that hot-compression efficiency of Al-Mg-Si alloy is significantly improved after compression beyond 250 °C, because no Mg/Si precipitates evolved. © 2019, ASM International.

Journal of Materials Engineering and Performance

Hot-Compression Response of Solution-Treated Al-Mg-Si Alloy

In the present work, ultrafine grained Al 6082 alloy was produced by cryorolling (CR), room temperature rolling (RTR), CR + annealing (CR + AN) at 200 °C and RTR + annealing (RTN + AN) at 200 °C processes to study the effects of metallurgical factors (ultrafine grain structure, precipitates and secondary phase particles) on its low cycle fatigue behavior. Various characterization techniques such as the transmission electron microscopy, electron back scattered diffraction, scanning electron microscopy and differential scanning calorimetry were used to investigate the low cycle fatigue (LCF) behavior of the 6082 Al alloy. It was observed that the sample produced via CR + AN exhibits the highest LCF life when compared to the other samples investigated. The improvement in the LCF life of the 6082 Al alloy after CR + AN is attributed to the presence of small sized Si-rich precipitates, secondary phase particles, sub grains formation (200–400 nm) and high stored energy (32.16 × 10−4 J/mol). © 2018 Elsevier Ltd

International Journal of Fatigue

The influence of metallurgical factors on low cycle fatigue behavior of ultra-fine grained 6082 Al alloy

Effects of cryorolling (CR) and followed by annealing (CR + AN) on the high cycle fatigue strength of bulk ultrafine grained (UFG) Al 2014 alloy were investigated in the present work. Al 2014 alloy was cryorolled (CR) for the thickness reduction of 75% at liquid nitrogen temperature (− 196 °C). The cryorolled (CR) samples were heat treated for the temperature range of 100–250 °C for the duration of 45 min in order to investigate its influence on tensile strength, yield strength and high cycle fatigue behavior. The microstructural characterization of the alloy was made through TEM and FESEM. The cryorolled (CR) sample shows the improved high cycle fatigue strength as compared to ST alloy due to the formation of ultrafine grain (UFG) microstructure. The reduced flaw size in UFG prevents accumulation of stress concentration near the crack tip. However, the improvement in high cycle fatigue properties of cryorolled followed by annealed (CR + AN) alloy up to 200 °C as compared to solution treated (ST) alloy observed is due to improvement in crack growth resistance facilitated by crack tip/precipitate interaction at grain boundaries (GBs). The high cycle fatigue strength gradually decreases with increasing annealing temperature from 100 to 250 °C, due to gradual coarsening of metastable precipitate (θ′ phase), which transformed in to stable coarser precipitate ‘θ’ phase at 250 °C. © 2017

Influence of cryorolling and followed by annealing on high cycle fatigue behavior of ultrafine grained Al 2014 alloy

The mechanical and corrosion behavior of Al alloy 6082-T6 subjected to solution heat treating condition at temperatures varying from 400 to 600 °C and soaking times of 3–24 h have been investigated. Solution heat treating at 550 °C for 24 h led to the dissolution of the Mg2Si and AlSi6Mg3Fe precipitates into the matrix, and the Al12(FeMn)3Si2 phase transformed into Al85(Fe0.28Mn0.72)14Si phase. The solution-treated alloy showed equiaxed grain morphology with an average grain size of 85.7 µm. Increasing the solution heat treating temperature beyond 550 °C caused a reduction in corrosion resistance of the alloy. The pitting potential increased due to the presence of the anodic phase Mg2Si (dissolved at 550 °C) in Al matrix and it decreased with the formation of cathodic phases such as AlSi6Mg3Fe and Al12(FeMn)3Si2 (dissolved at 550 °C/24 h) in the alloy. General corrosion resistance of the alloy increased with decreasing Mg2Si concentration in the Al matrix. The optimum solution heat treating condition of 550 °C for 24 h resulted in an improvement in hardness (63 VHN), ultimate tensile strength (UTS—208 MPa), and pitting potential (−675 mV) and uniform corrosion potential (−1.255 mV) of 6082 Al alloy. © 2015, Springer Science+Business Media New York and ASM International.

Metallography, Microstructure, and Analysis

Effect of Solution Treatment on Mechanical and Corrosion Behaviors of 6082-T6 Al Alloy

In the present study, recovery, recrystallisation, grain growth, mechanical, and corrosion resistance of 6082 Al alloy subjected to cryorolling (CR) and annealing (AN) treatment were investigated. CR was performed to produce ultrafine grained structure and subsequently, AN treatment was given to investigate its influence on recovery, recrystallisation, and grain growth. The recovery and recrystallisation occurs between 110 and 250 C and 250-300 C respectively, where as grain growth starts from 300 C due to insoluble dispersions (AlMn &amp; AlMnSi) and Mg2Si precipitates in the alloy as evident from Differential scanning calorimetry (DSC), Electron back scattered diffraction (EBSD), hardness and Transmission electron microscopy (TEM) results. CR 6082 Al alloy has showed increased hardness of 120 VHN and ultimate tensile strength of 353 MPa. Annealing of CR 6082 Al alloy at 150 C exhibited maximum hardness, ultimate tensile strength (UTS) and ductility of 127 VHN, 362.5 MPa, and 11%, respectively. CR of the 6082 Al alloy has produced high density of dislocation and increase in grain boundary area, which enabled the formation of dense oxide film on surface, enhancing its corrosion resistance. CR samples annealed at 350 C shows excellent corrosion resistance as compared to as deformed Al alloy. © 2015 Elsevier B.V. All rights reserved.

Materials Chemistry and Physics

Effect of cryorolling and annealing on recovery, recrystallisation, grain growth and their influence on mechanical and corrosion behaviour of 6082 Al alloy

Cast Al-Si alloys often show poor tensile strength, less ductility and poor fatigue performance due to cast microstructure and presence of porosity. An attempt has been made to improve mechanical properties of a cast hypoeutectic Al-Si alloy (A356) by cryorolling. As cast Al-Si alloy (A356) processed by cryorolling at different imposed strain levels was subjected to microstructural analysis and mechanical testing. Cryorolling resulted in break up and uniform distribution of coarse acicular eutectic particles in the aluminium matrix, elimination of casting porosity, microstructural refinement and significant accumulation of dislocation density. These microstructural changes resulted in significant improvement in the strength (248%) and ductility (37%). The influence of cryorolling on mechanism of microstructural modification, strengthening mechanism and failure mechanism are studied in detail. © 2015 Elsevier B.V.

Journal	Data powered by TypesetMaterials Characterization
Publisher	Data powered by TypesetElsevier Inc.
ISSN	10445803
Open Access	No