Multi-stage heat treatment of aluminum alloy AA7049

Ranganatha, R.; Kumar, V. Anil; Nandi, Vaishaki S.; Bhat, R. Raghavendra; Muralidhara, B. K.

doi:10.1016/s1003-6326(13)62632-1

Cited by 57 publications

(14 citation statements)

References 12 publications

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“…The presence of fine precipitate structure of GP zones and metastable phase h 0 are attributable to the strengthening of alloy. The majority of the precipitates are of h 0 type and more stable GP-II zones are present in smaller amount [8]. The base metal (T7) sample contains the coarser precipitates which uniformly distribute inside the grains.…”

Section: Tensile Testsmentioning

confidence: 99%

Microstructure, mechanical and corrosion behavior of high strength AA7075 aluminium alloy friction stir welds – Effect of post weld heat treatment

2015

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High strength aluminium alloy AA7075 (AleZneMgeCu) is a precipitate hardenable alloy widely used in the aerospace, defense, marine and automobile industries. Use of the heat treatable aluminium alloys in all these sectors is ever-increasing owing to their excellent strength-toweight ratio and reasonably good corrosion resistance. The shortage in corrosion resistance, however, usually poses negative concern about their reliability and lifetime when they service in the variable marine environments. These alloys also exhibit low weldability due to poor solidification microstructure, porosity in fusion zone and lose their mechanical properties when they are welded by fusion welding techniques. Friction stir welding (FSW) is a reliable technique to retain the properties of the alloy as the joining takes place in the solid state. The welds are susceptible to corrosion due to the microstructural changes in the weld nugget during FSW. In this work, the effect of post weld treatments, viz., peak aging (T6) and retrogression & reaging (RRA), on the microstructure, mechanical properties and pitting corrosion has been studied. Friction stir welding of 8 mm-thick AA7075 alloy was carried out. The microstructural changes of base metal and nugget zone of friction stir welds were studied using optical microscopy, scanning electron microscopy and transmission electron microscopy. Tensile and hardness test of base metal and welds has been carried out. Pitting corrosion resistance was determined through dynamic polarization test.It was observed that the hardness and strength of weld were observed to be comparatively high in peak aged (T6) condition but the welds showed poor corrosion resistance. The resistance to pitting corrosion was improved and the mechanical properties were maintained by RRA treatment. The resistance to pitting corrosion was improved in RRA condition with the minimum loss of weld strength.

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Section: Tensile Testsmentioning

confidence: 99%

Microstructure, mechanical and corrosion behavior of high strength AA7075 aluminium alloy friction stir welds – Effect of post weld heat treatment

2015

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“…"The longer retrogression time during the RRA treatment leads to a combination of grain boundary η precipitate coarsening, which resembles the precipitates formed in the T73 temper and the η-η′ precipitates distribution in the matrix which looks like the precipitates formed in the T6 temper. This combination results in good performance with respect to resistance to stress corrosion cracking and the thermodynamic stability as well as mechanical strength" [46]. The TEM study results of Kumar et al [30] on AA7075 in different heat treatment conditions show the dispersion of precipitates η′ and η in the alloy matrix along with coexistent coarser and sparsely distributed η precipitates locating at the grain boundaries, together with precipitate-free zones (PFZs), Figure 7.…”

Section: Microstructurementioning

confidence: 97%

“…The dimensions and shape factors of precipitates detected in L-T plane of AA7050 and AA7075 alloys. Referring to Ranganatha et al [46], by retrogression and re-aging (RRA) heat treatment, the resistance to SCC is enhanced without losing yield or tensile strength. "The longer retrogression time during the RRA treatment leads to a combination of grain boundary η precipitate coarsening, which resembles the precipitates formed in the T73 temper and the η-η′ precipitates distribution in the matrix which looks like the precipitates formed in the T6 temper.…”

Section: Microstructurementioning

confidence: 99%

Fracture Behavior Evaluation of High-Strength 7050 and 7075 Aluminum Alloys Using V-Notched Specimen

Abachi¹,

Naseri²,

Purazrang³

et al. 2016

Fracture Mechanics - Properties, Patterns and Behaviours

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The fracture behaviors of high-strength 7050 and 7075 aluminum alloys (AA7050 and AA7075) were investigated using small size, V-notched tear specimens. In accordance with ASTM B871-01 standard test method, the thickness and notch angle were selected as 6.35 mm and 60°, respectively. All tear specimens (also called Kahn specimens) were machined in L-T orientation and the mechanical tests were conducted at RT. To evaluate crack propagation route during failure process, interrupted tear tests were also conducted on AA7075. The subsized cylindrical tension test specimens were machined in L direction of the bulk materials to study the elastic-plastic behavior of the alloys in accordance with ASTM B 557M-98 standard test method. The microstructures of T73651 and T6 heat-treated alloys were examined using optical microscopy and SEM. The precipitate characterization of heat-treated specimens was performed using Clemex image analysis software. The rupture mechanisms were also studied by examination of specimen fracture surfaces using SEM. According to the results, the amount, size and distribution of intermetallic particles have been identified as the important factors on failure of the examined alloys. Both examined alloys show the same damage initiation mechanism; however, the failure mechanism is different to some extent. Depending on the stress condition, two major failure micromechanisms, i.e., "internal necking mechanism" and "void sheet mechanism," are prevailing for both alloys. The results of mechanical tests and determination of tear strength to 0.2% tensile yield strength ratio made it possible to evaluate specimens' notch toughness. The comparison of specimens' resistance to stable crack propagation and subsequent fracture in the presence of crack-like stress concentrator was provided using tear test data.

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“…Besides, high-strength aluminum alloys in the peak strength state are known to be highly susceptible to stress corrosion cracking (SCC). However, the susceptibility of T6 temper to corrosion can be alleviated through the utilization of over-aged T73 temper, which provides improved corrosion resistance, but with a 10%-15% reduction in strength [5]. Therefore, a study of effect of heat treatment, especially over-aging, on the anisotropy of high-strength aluminum alloys during plastic forming is necessary.…”

Section: Introductionmentioning

confidence: 99%

Effect of Heat Treatment on the In-Plane Anisotropy of As-Rolled 7050 Aluminum Alloy

Wang

2016

Metals

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Abstract:Tensile tests were conducted on both as-quenched and over-aged 7050 aluminum alloy to investigate the effect of heat treatment on the in-plane anisotropy of as-rolled 7050 aluminum alloy. The results showed that the tensile direction has limited effect on mechanical properties of the as-quenched 7050 aluminum alloy. The in-plane anisotropy factors (IPA factor) of tensile strength, yield strength, and elongation in as-rolled 7050 aluminum alloy fluctuate in the vicinity of 5%. The anisotropy of the as-quenched 7050 aluminum alloy is mainly affected by the texture according to single crystal analysis based on the Schmid factor method. Besides, the IPA factor of the elongation in the over-aged 7050 aluminum alloy reaches 11.6%, illustrating that the anisotropy of the over-aged 7050 aluminum alloy is more prominent than that of the as-quenched. The occurrence of the anisotropy in the over-aged 7050 aluminum alloy is mainly attributed to the microstructures. which are characterized by visible precipitate free zones (PFZs) and coarse precipitates in (sub)grain boundaries.

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Multi-stage heat treatment of aluminum alloy AA7049

Cited by 57 publications

References 12 publications

Microstructure, mechanical and corrosion behavior of high strength AA7075 aluminium alloy friction stir welds – Effect of post weld heat treatment

Microstructure, mechanical and corrosion behavior of high strength AA7075 aluminium alloy friction stir welds – Effect of post weld heat treatment

Fracture Behavior Evaluation of High-Strength 7050 and 7075 Aluminum Alloys Using V-Notched Specimen

Effect of Heat Treatment on the In-Plane Anisotropy of As-Rolled 7050 Aluminum Alloy

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