Mechanisms of abnormal grain growth in friction-stir-welded aluminum alloy 6061-T6

A solid-state repair technique based on surface friction welding is investigated in depth to achieve excellent mechanical properties of damaged 7A52 aluminum alloy. The results show that the yield strength and tensile strength along the repair direction are 436 MPa and 502 MPa, respectively, at a rotational speed of 1400 rpm and a travel speed of 300 mm/min, which are about 157.9% and 129.7% of those before the defects were repaired, respectively, while the elongation is 17.2% compared to the base material. Perpendicular to the repair direction, the yield strength and tensile strength are 254 MPa and 432 MPa, which are 111.4% and 129.7% of those before the defects were repaired, respectively, while the elongation is 11.8% compared to the base material. The mechanical properties of the repaired areas are still improved compared to those of the defect-free sheets. On the one hand, this is attributed to the dynamic recrystallization of the nugget zone due to the thermo-mechanical coupling, resulting in the formation of a fine, equiaxed grain structure; on the other hand, the precipitated Mg2Si phase, which is incoherent within the base material, transforms into the Al12(Fe, Mn)3Si phase, as well as the precipitation of the Al6Mn phase and η′ phase, resulting in the enhancement of the properties. The material fracture at the junction of the nugget zone and the heat-affected zone occurs after repair, which is attributed to the significant difference in the texture of the nugget zone and the heat-affected zone, as well as to the stress concentration at the junction.

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Microstructure Evolutionmentioning

confidence: 99%

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Microstructure Evolution and Mechanical Properties of 7A52 Aluminum Alloy Thin Sheet Repaired with Friction Stir Surfacing

Li,

Shi,

Han

et al. 2024

“…For example, the relationship between the grain size and properties such as the flow stress [11,12], mechanical properties [13], thermal cracking [14], and deformation temperature [15] have been examined. Although grain refinement can enhance the performance of aluminum alloys, abnormal grain growth can lead to structural defects, severely affecting the mechanical properties of the alloys [16][17][18]. With the development of computers and information technology, mathematical models describing the structure and properties are the basis for the accurate prediction and control of the structure and properties of aluminum alloys in the production process, and thus, they have become a focus of attention [19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Predictive Modeling of Tensile Strength in Aluminum Alloys via Machine Learning

Fu,

Zhu,

Zhang

et al. 2023

Aluminum alloys are widely used due to their exceptional properties, but the systematic relationship between their grain size and their tensile strength has not been thoroughly explored in the literature. This study aims to fill this gap by compiling a comprehensive dataset and utilizing machine learning models that consider both the alloy composition and the grain size. A pivotal enhancement to this study was the integration of hardness as a feature variable, providing a more robust predictor of the tensile strength. The refined models demonstrated a marked improvement in predictive performance, with XGBoost exhibiting an R2 value of 0.914. Polynomial regression was also applied to derive a mathematical relationship between the tensile strength, alloy composition, and grain size, contributing to a more profound comprehension of these interdependencies. The improved methodology and analytical techniques, validated by the models’ enhanced accuracy, are not only relevant to aluminum alloys, but also hold promise for application to other material systems, potentially revolutionizing the prediction of material properties.

“…Remarkably, the stir zone material may experience secondary deformation associated with the tool shoulder [16]. This effect is most pronounced at the upper weld surface and may produce a fine-grained microstructural layer in this area [17]. After FSW, the welded material often experiences a static microstructural coarsening upon cooling from FSW temperature to ambient conditions [3,[18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Grain Structure Evolution in 6013 Aluminum Alloy during High Heat-Input Friction-Stir Welding

Kalinenko,

Dolzhenko,

Malopheyev

et al. 2023

Self Cite

This work was undertaken to evaluate the influence of friction-stir welding (FSW) under a high-heat input condition on microstructural evolution. Given the extreme combination of deformation conditions associated with such an FSW regime (including the highest strain, temperature, and strain rate), it was expected to result in an unusual structural response. For this investigation, a commercial 6013 aluminum alloy was used as a program material, and FSW was conducted at a relatively high spindle rate of 1100 rpm and an extremely low feed rate of 13 mm/min; moreover, a Ti-6Al-4V backing plate was employed to reduce heat loss during welding. It was found that the high-heat-input FSW resulted in the formation of a pronounced fine-grained layer at the upper weld surface. This observation was attributed to the stirring action exerted by the shoulder of the FSW tool. Another important issue was the retardation of continuous recrystallization. This interesting phenomenon was explained in terms of a competition between recrystallization and recovery at high temperatures. Specifically, the activation of recovery should reduce dislocation density and thus retard the development of deformation-induced boundaries.