A TEM study of precipitation in Al–Mg–Si alloys

Yao, Ji Yong; Graham, D.A.; Rinderer, Barbara; Couper, Malcolm J.

doi:10.1016/s0968-4328(00)00095-0

Cited by 41 publications

(28 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[13] Previous DSC studies showed that the occurrence of b¢¢ and b¢ dissolution/precipitation produced a strong exothermic peak at~250°C and~290°C, respectively. [2,69,70] Therefore, the thermal cycle above 250°C, like the present FSW, would result in the dissolution of the needle-shaped precipitates in the Al-Mg-Si alloy, as shown in Figures 4 and 5.…”

Section: A Microstructural Characteristicsmentioning

confidence: 77%

See 1 more Smart Citation

Microstructure and Low-Cycle Fatigue of a Friction-Stir-Welded 6061 Aluminum Alloy

Feng

Chen

2010

Metall Mater Trans A

View full text Add to dashboard Cite

Strain-controlled low-cycle fatigue (LCF) tests and microstructural evaluation were performed on a friction-stir-welded 6061Al-T651 alloy with varying welding parameters. Friction stir welding (FSW) resulted in fine recrystallized grains with uniformly distributed dispersoids and dissolution of primary strengthening precipitates b¢¢ in the nugget zone (NZ). Two low-hardness zones (LHZs) appeared in the heat-affected zone (HAZ) adjacent to the border between the thermomechanically-affected zone (TMAZ) and HAZ, with the width decreasing with increasing welding speed. No obvious effect of the rotational rate on the LHZs was observed. Cyclic hardening of the friction-stir-welded joints was appreciably stronger than that of base metal (BM), and it also exhibited a two-stage character where cyclic hardening of the frictionstir-welded 6061Al-T651 alloy at higher strain amplitudes was initially stronger followed by an almost linear increase of cyclic stress amplitudes on the semilog scale. Fatigue life, cyclic yield strength, cyclic strain hardening exponent, and cyclic strength coefficient all increased with increasing welding speed, but were nearly independent of the rotational rate. Most friction-stirwelded joints failed along the LHZs and exhibited a shear fracture mode. Fatigue crack initiation was observed to occur from the specimen surface, and crack propagation was mainly characterized by the characteristic fatigue striations. Some distinctive tiremark patterns arising from the interaction between the hard dispersoids/inclusions and the relatively soft matrix in the LHZ under cyclic loading were observed to be present in-between the fatigue striations.

show abstract

Section: A Microstructural Characteristicsmentioning

confidence: 77%

“…[1][2][3] 6xxx-series aluminum alloy accounts for a large percentage of the total aluminum production in the world. [4] The application of 6xxx-series aluminum alloy in the aerospace and automotive industries involves welding and joining.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Low-Cycle Fatigue of a Friction-Stir-Welded 6061 Aluminum Alloy

Feng

Chen

2010

Metall Mater Trans A

View full text Add to dashboard Cite

show abstract

“…The presence of Sr has no significant effect on the formation of the Mg 2 Si phase; the latter has a mostly needlelike morphology and is precipitated along favorable crystallographic Ͻ100Ͼ direction. [12,13] The length of the Mg 2 Si particles ranges from 700 to 2000 nm. In addition to needles, few spherical Mg 2 Si particles are also observed.…”

Section: A Microstructural Evolutionmentioning

confidence: 99%

Effects of rapid heating on solutionizing characteristics of Al-Si-Mg alloys using a fluidized bed

Chaudhury

Apelian

2006

Metall Mater Trans A

View full text Add to dashboard Cite

Effects of rapid heat transfer using a fluidized bed on the heat-treating response of Al-Si-Mg alloys (both unmodified and Sr modified) were investigated. The heating rate in the fluidized bed is greater than in conventional air convective furnaces. Particle size analyses of eutectic Si showed that the high heating rate during fluidized bed solution heat treatment causes faster fragmentation and spherodization of Si particles compared to conventional air convective furnaces. The mechanism of Si fragmentation through fluidized bed processing is through both brittle fracture and neck formation and its propagation. In contrast to this, the mechanism of Si fragmentation using a conventional air convective furnace is through neck formation and propagation. The Sr-modified D357 alloy showed a faster spherodizing rate than the unmodified alloy. Thermal analyses showed an exothermic reaction during solution heat treatment using a fluidized bed due to recrystallization, and coarsening of eutectic Al grains. Whereas the alloy solutionized using a conventional air convective furnace showed two exothermic reactions, one due to annihilation of point defects and the other due to recrystallization, and coarsening of the eutectic grains in the aluminum matrix. The recrystallization temperature of the alloy solutionized in the fluidized bed is lower than those in the conventional air convective furnace. Both tensile strength and elongation of fluidized bed solutionized alloys are greater than those solutionized using the air convective furnace. The optimum heat-treatment time for T4 temper using a fluidized bed for unmodified and Sr-modified alloy was reduced to 60 and 30 minutes, respectively.

show abstract

“…Several of these studies have been reported. [28][29][30][31][32] Recrystallisation is mostly evidenced by using high resolution scanning electron microscopy (SEM) in combination with electron backscatter diffraction (EBSD); crystallisation and devitrivication is best evidenced by X-ray diffraction; and nanocrystallisation is evidenced by TEM with SAD. Melting reactions can often be indirectly evidenced by studying eutectic structures in a sample that is rapidly solidified by quenching after having (partially) melted, using SEM (possibly in combination with EDS).…”

Section: Identification Of Thermal Effectsmentioning

confidence: 99%

Analysis of aluminium based alloys by calorimetry: quantitative analysis of reactions and reaction kinetics

Starink¹

2004

International Materials Reviews

286

108

View full text Add to dashboard Cite

Differential scanning calorimetry (DSC) and isothermal calorimetry have been applied extensively to the analysis of light metals, especially Al based alloys. Isothermal calorimetry and differential scanning calorimetry are used for analysis of solid state reactions, such as precipitation, homogenisation, devitrivication and recrystallisation; and solid-liquid reactions, such as incipient melting and solidification, are studied by differential scanning calorimetry. In producing repeatable calorimetry data on Al alloys, sample preparation, reproducibility and baseline drift need to be considered in detail. Calorimetry can be used effectively to study the different solid state reactions and solid-liquid reactions that occur during the main processing steps of Al based alloys (solidification, homogenisation, precipitation). Also, devitrivication of amorphous and ultrafine grained Al based powders and flakes can be studied effectively. Quantitative analysis of the kinetics of reactions is assessed through reviewing the interrelation between activation energy analysis methods, equivalent time approaches, impingement parameter approaches, mean field models for precipitation, the Johnson-Mehl-Avrami-Kolmogorov model, as well as novel models which have not yet found application in calorimetry. Differential scanning calorimetry has occasionally been used in attempts to measure the volume fractions of phases present in Al based alloys, and attempts at determining volume fractions of intermetallic phases in commercial alloys and amounts of devitrified phase in glasses are reviewed. The requirements for the validity of these quantitative applications are also reviewed.Keywords: Differential scanning calorimetry, Precipitation, Aluminium, Modelling, Transformation IMR/419 IntroductionCalorimetry is an analysis technique that is part of a group of techniques collectively known as thermal analysis methods. In its broadest sense, thermal analysis refers to the measurement of changes in properties of substances under a controlled temperature program. Thermal analysis techniques can be classified according to the type of temperature program that the sample is subjected to and the measured (output) signal. The most commonly used temperature programs are either isothermal hold or heating (scanning) at constant rate, while more recently, temperature modulated scanning and reaction controlled heating have also found application. The signals measured in thermal analysis can include heat flows, temperature changes, mass, evolved gasses, length changes, elastic modulus, and many other properties that characterise properties or reactions of interest. Calorimetry refers to thermal analysis methods that measure the heat evolution from a sample under a controlled temperature program. The two most often applied calorimetry techniques are isothermal calorimetry and differential scanning calorimetry (DSC), which, as the name suggests, is by definition non-isothermal (i.e. a temperature scan). Apart from the more common applications to polymers,...

show abstract

A TEM study of precipitation in Al–Mg–Si alloys

Cited by 41 publications

References 8 publications

Microstructure and Low-Cycle Fatigue of a Friction-Stir-Welded 6061 Aluminum Alloy

Microstructure and Low-Cycle Fatigue of a Friction-Stir-Welded 6061 Aluminum Alloy

Effects of rapid heating on solutionizing characteristics of Al-Si-Mg alloys using a fluidized bed

Analysis of aluminium based alloys by calorimetry: quantitative analysis of reactions and reaction kinetics

Contact Info

Product

Resources

About