Influence of Microstructural Inhomogeneity on Fracture Behaviour in SSM-HPDC Al-Si-Cu-Fe Component with Low Si Content

Payandeh, Mostafa; Jarfors, Anders E. W.; Wessén, Magnus

doi:10.4028/www.scientific.net/ssp.217-218.67

Cited by 8 publications

(7 citation statements)

References 14 publications

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“…Three different phenomena lead to transverse macrosegregation: skin effect [12], sponge effect [13,50] and shearing band during melt flow that lead to porosity or eutectic-rich segregation band [52]. Study of transverse macrosegregation in different positions of the same Rheo-HPDC component performed by Payandeh et al [53] showed that the thickness of the surface segregation layer increases by increasing the liquid faction. Govender et al [54] also reported the existence of a surface layer consisting of mainly liquid or eutectic phase in SSM-HPDC A356 Alloy.…”

Section: Microstructural Featuresmentioning

confidence: 99%

Effect of Segregation and Surface Condition on Corrosion of Rheo-HPDC Al–Si Alloys

Eslami

Payandeh

Deflorian

et al. 2018

Metals

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Corrosion properties of two Al-Si alloys processed by Rheo-high pressure die cast (HPDC) method were examined using polarization and electrochemical impedance spectroscopy (EIS) techniques on as-cast and ground surfaces. The effects of the silicon content, transverse and longitudinal macrosegregation on the corrosion resistance of the alloys were determined. Microstructural studies revealed that samples from different positions contain different fractions of solid and liquid parts of the initial slurry. Electrochemical behavior of as-cast, ground surface, and bulk material was shown to be different due to the presence of a segregated skin layer and surface quality.

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Section: Microstructural Featuresmentioning

confidence: 99%

Effect of Segregation and Surface Condition on Corrosion of Rheo-HPDC Al–Si Alloys

Eslami

Payandeh

Deflorian

et al. 2018

Metals

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“…% during solution treatment, which is expected to result in a higher fraction of θ'' precipitates formed during ageing. The influence of these Cu-containing precipitates on diffusivity depends on their size [5,6]. When they become large, they will have a small influence similar to that of Al2Cu particles.…”

Section: T6 Treated Conditionmentioning

confidence: 99%

“…by precipitation, generally leads to an increase in thermal conductivity as the number of scattering centers decreases [4]. The formation of GP zones, for example during natural ageing is an exception where thermal conductivity has been reported to decrease despite a decrease of atoms in solid solution [5,6]. Thermal conductivity thus depends not only on alloy composition but also on the microstructure formed during solidification and on its modification during subsequent transformations in solid state, which makes thermal conductivity of a real component very complex property to understand.…”

Section: Introductionmentioning

confidence: 99%

Influence of microstructure and heat treatment on thermal conductivity of rheocast and liquid die cast Al-6Si-2Cu-Zn alloy

Payandeh

Sjölander

Jarfors

et al. 2016

International Journal of Cast Metals Research

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This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. Citation for the original published paper (version of record):Payandeh, M., Sjölander, E., Jarfors, A., Wessén, M. (2016) Influence of microstructure and heat treatment on thermal conductivity of rheocast and liquid die cast Al-6Si-2Cu-Zn alloy. International Journal of Cast Metals AbstractThermal conductivity of a rheocast telecom component made from Stenal Rheo1 (Al-6Si-2Cu-Zn) alloy was investigated in as-cast, T5 and T6 conditions. Conventionally liquid die cast samples were used as reference material. In the as-rheocast condition, a thermal conductivity of 153 W/mK at room temperature was measured. A T5 treatment at 250 or 300°C increased thermal conductivity to 174 W/mK. A T6 treatment resulted in further increase in thermal conductivity to 182 W/mK. The liquid die cast material exhibited lower thermal conductivity and higher hardness for all conditions compared to the as-rheocast material.The microstructural investigation revealed that the rheocast material consisted of coarse α1-Al particles formed during slurry preparation and fine α2-Al particles formed during solidification in the die cavity. Macrosegregation was observed as different the ratio of α1-Al particles to α2-Al particles in different locations in the rheocast component. The relation between microstructural characteristics and thermal diffusivity was investigated by determination of local thermal conductivity in the rheocast component and ratio of α1-Al particles to α2-Al particles. The results revealed that regions of rheocast component with a high amount of α1-Al particles showed higher thermal conductivity. WDS measurement showed that α1-Al particles contains lower concentrations of both Si and Cu inside compare to α2-Al particles. The reduced amount of solutes in the α1-Al particles was therefore determined as the root cause to higher thermal conductivity.Silicon precipitation was confirmed using calorimetry and dilatometry to take place between 200 and 250°C. A linear relation between the fraction of Si precipitates formed and the increase in thermal diffusivity was obtained. Silicon in solid solution is shown to have a strong influence (negative) on thermal conductivity. As silicon was precipitated during the heat treatment, thermal conductivity increased. For an optimal combination of thermal and mechanical properties it is therefore important to use an ageing temperature above the temperature for Si precipitation.

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“…The smaller grain size of SSM castings also hinders the fatigue crack propagation due to the higher density of the grain boundaries, which results in the longer fatigue life of SSM castings compared to permanent mould castings [12,13]. Surface segregation is commonly found in direct-chill casting [14], HPDC [15][16][17], and SSM casting [18][19][20] products and results in heterogeneous properties along the crosssection of the castings [14]. Gourlay et al [21] suggested that the surface segregation layer formation in HPDC results from a combination of inverse segregation and exudation mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Fatigue Crack Initiation on Semi-Solid Al–7Si–Mg Castings

Santos

Zhu

Zanella

et al. 2022

Metals

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Four-point bending fatigue tests were performed on semi-solid Al–7Si–Mg castings with varying magnesium contents and heat treatment conditions. Additionally, the effect of anodising on the fatigue resistance of semi-solid Al–7Si–Mg castings was evaluated. Fracture surface and microstructure analysis showed that fatigue crack initiation occurred mainly at the periphery of regions of positive macrosegregation at the casting surface, resulting most likely from exudation. The microstructure of these macrosegregation regions was mostly eutectic and was frequently found surrounded by a layer of oxides. This layer of oxides promoted weak bonding between the macrosegregation region and the surrounding material and acted as a crack initiation site. In this study, primary α-Al globule agglomerates at the casting surface and surrounded by a layer of oxides also promoted fatigue crack initiation. Fatigue resistance of semi-solid Al–7Si–Mg castings in the T5 and T6 conditions increased with the increase in the magnesium content of the alloy from 0.3 to 0.45 wt.% due to the higher precipitation hardening response. However, the increase in the magnesium content from 0.45 to 0.6 wt.% resulted in a slight decrease in the fatigue resistance. The oxide layer formed during anodising had no significant effect on the fatigue resistance of the semi-solid Al–7Si–Mg castings in this study due to the dominant effect of the macrosegregation regions on fatigue crack initiation.

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Influence of Microstructural Inhomogeneity on Fracture Behaviour in SSM-HPDC Al-Si-Cu-Fe Component with Low Si Content

Cited by 8 publications

References 14 publications

Effect of Segregation and Surface Condition on Corrosion of Rheo-HPDC Al–Si Alloys

Effect of Segregation and Surface Condition on Corrosion of Rheo-HPDC Al–Si Alloys

Influence of microstructure and heat treatment on thermal conductivity of rheocast and liquid die cast Al-6Si-2Cu-Zn alloy

Fatigue Crack Initiation on Semi-Solid Al–7Si–Mg Castings

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