Effect of metallurgical parameters on the hardness and microstructural characterization of as-cast and heat-treated 356 and 319 aluminum alloys

Tash, Mahmoud M.; Samuel, F. H.; Mucciardi, F.; Doty, H. W.

doi:10.1016/j.msea.2006.08.054

Cited by 130 publications

(87 citation statements)

References 12 publications

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“…Strontium, Sr, is often used as a chemical modifier and small additions of 50-300 ppm are often made [13]. The Sr concentration needed to obtain a fibrous morphology depends on the purity of the melt; Mg for example negates some of the modifying effect [13,14]. The fibrous morphology obtained through Sr modification is much easier to fragment and spheroidize during solution treatment and the solution treatment time can be shortened [11].…”

Section: Alloy Compositionmentioning

confidence: 99%

The heat treatment of Al–Si–Cu–Mg casting alloys

Sjölander

Seifeddine

2010

Journal of Materials Processing Technology

460

223

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Environmental savings can be made by increasing the use of aluminium alloys in the automotive industry as the vehicles can be made lighter. Increasing the knowledge about the heat treatment process is one task in the direction towards this goal. The aim of this work is to investigate and model the heat treatment process for Al-Si casting alloys. Three alloys containing Mg and/or Cu were cast using the gradient solidification technique to achieve three different coarsenesses of the microstructure and a low amount of defects.Solution treatment was studied by measuring the concentration of Mg, Cu and Si in the α-Al matrix using wavelength dispersive spectroscopy (WDS) after various times at a solution treatment temperature. A diffusion based model was developed which estimates the time needed to obtain a high and homogenous concentration of alloying elements for different alloys, temperatures and coarsenesses of the microstructure. It was shown that the yield strength after artificial ageing is weakly dependent on the coarseness of the microstructure when the solution treatment time is adjusted to achieve complete dissolution and homogenisation.The shape and position of ageing curves (yield strength versus ageing time) was investigated empirically in this work and by studying the literature in order to differentiate the mechanisms involved. A diffusion based model for prediction of the yield strength after different ageing times was developed for Al-Si-Mg alloys. The model was validated using data available in the literature. For Al-Si-Cu-Mg alloys further studies regarding the mechanisms involved need to be performed.Changes in the microstructure during a heat treatment process influence the plastic deformation behaviour. The Hollomon equation describes the plastic deformation of alloys containing shearable precipitates well, while the Ludwigson equation is needed when a supersaturated solid solution is present. When non-coherent precipitates are present, none of the equations describe the plastic deformation well. The evolution of the storage rate and recovery rate of dislocations was studied and coupled to the evolution of the microstructure using the Kocks-Mecking strain hardening theory.

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Section: Alloy Compositionmentioning

confidence: 99%

The heat treatment of Al–Si–Cu–Mg casting alloys

Sjölander

Seifeddine

2010

Journal of Materials Processing Technology

460

223

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“…The aluminum alloys are commonly used in the automotive industry, from its excellent combination of strength and ductility 1 , moreover, of their high strength/weight ratio, corrosion resistance, excellent thermal conductivity and high cast ability allows the casting of complex forms 2 .…”

Section: Introductionmentioning

confidence: 99%

“…The effects of heat treatments in Al-Si-Cu alloys have been studied by different techniques from different authors 1,2,6,7 . The authors reported that β-Mg 2 Si, θ-Al 2 Cu, Al 2 CuMg, and Al 4 CuMg 5 Si 4 phases are dissolved during the SHT and are highly responsible of hardening of Al-Si-Cu-Mg, e.g.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Microstructure in Al-Si-Cu System Modified with a Transition Element Addition and its Effect on Hardness

et al. 2016

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The effect of Ni 1-2 wt.% addition on the microstructure and hardness of the aged A319 alloy were studied. Characterization analyses by x-ray diffraction, optical microscopy and scanning electron microscopy suggest clearly that Ni addition forms Al-Ni-Cu-Fe, Al-Cu-Ni and Al-Ni intermetallic compounds that correlates well with equilibria conditions. Analyses by transmission electron microscopy show that aging heat treatment promotes microstructural changes in morphology, size, and spatial distribution of precipitates. Vickers micro-hardness test of Ni 1 and 2 wt.% specimens have a hardness increase from that of A319 alloy of ~6-8% with mean values of 140.98 and 142.93 HV, respectively.

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“…The presence of b-Al 5 FeSi intermetallics increases hardness and reduces impact strength and machinability, but also lowers the soldering of the casting in permanent molds and high pressure die casting. The possibility of changing b-Al 5 FeSi plates into less harmful phases having more compact morphology (e.g., Chinese script [10] ) is one way to obtain better quality of the castings.…”

Section: Introductionmentioning

confidence: 99%

Interplay Between Melt Flow and the 3D Distribution and Morphology of Fe-Rich Phases in AlSi Alloys

Mikołajczak

Ratke

2014

Metall Mater Trans A

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The presence of Fe aids in establishing the mechanical and physical properties of AlSi alloys and is also one of the main impurities leading to formation of b-Al 5 FeSi intermetallics. This study aims to understand the effect of fluid flow on the dendritic microstructure with intermetallics in Al-5/7/9 wt pct Si-0.2/0.5/1.0 wt pct Fe alloys that are directionally solidified under defined thermal and fluid flow conditions. We made extensive use of 3D X-ray tomography to obtain a better insight into the morphology and formation of the intermetallics. Three-dimensional (3-D) distribution of intermetallics presented here shows that the growth of large b-Al 5 FeSi due to forced flow occurs in the eutectic specimen center and together with an increase in the number density of b precipitates. The 3D reconstructions have verified the b shaped to be curved, bent with twining, branched, and to have imprints, holes, and propeller-shaped platelets. The 3D views showed that hole-shaped b arose from the lateral growth around a-Al dendrites. These views also confirmed the phenomenon of shortening of b as an effect of flow in the dendritic region, where b could be fragmented or completely remelted, and ultimately resulting in microstructures with shorter b-Al 5 FeSi and increases in number density. The analysis revealed an interaction between melt flow, 3D distribution, and the morphology of b-Al 5 FeSi. The growth of a large and complex group of b intermetallics can reduce the melt flow between dendrites and strengthen pore nucleation and eutectic colonies nucleation, leading to lower permeability of the mushy zone and increased porosity in the castings.

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Effect of metallurgical parameters on the hardness and microstructural characterization of as-cast and heat-treated 356 and 319 aluminum alloys

Cited by 130 publications

References 12 publications

The heat treatment of Al–Si–Cu–Mg casting alloys

The heat treatment of Al–Si–Cu–Mg casting alloys

Evolution of Microstructure in Al-Si-Cu System Modified with a Transition Element Addition and its Effect on Hardness

Interplay Between Melt Flow and the 3D Distribution and Morphology of Fe-Rich Phases in AlSi Alloys

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