| 1. |
- Jarfors, Anders, 1963-, et al.
(författare)
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Influence of process parameters on surface appearance and roughness of a low Si containing Al-alloy, in semisolid casting
- 2015
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Ingår i: Solid State Phenomena. - Switzerland : Trans Tech Publications Inc.. - 1012-0394 .- 1662-9779. ; 217-218, s. 318-324
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Tidskriftsartikel (refereegranskat)abstract
- The visual appearance and surface roughness were experimentally investigated inindustrial scale for a low silicon containing aluminium alloy cast in semisolid state integrated withHPDC machine. A visual comparative technique and surface roughness in the form of the Rq valuewere used to evaluate the surface appearance and the surface roughness respectively. The resultswere investigated statistically to find significant models. It was shown that high quality appearance,following a comparative scale, was possible using high die temperature and high injection speed. Itwas also found that improving the surface roughness will deteriorate the visual appearance.
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| 2. |
- Maryam, Eslami, et al.
(författare)
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Effect of Segregation and Surface Condition on Corrosion of Rheo-HPDC Al–Si Alloys
- 2018
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 3. |
- Payandeh, Mostafa, 1981-, et al.
(författare)
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Effect of superheat on melting rate of EEM of Al alloys during stirring using the RheoMetal process
- 2013
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Ingår i: Solid State Phenomena. - 1012-0394 .- 1662-9779. ; 192-193, s. 392-397
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Tidskriftsartikel (refereegranskat)abstract
- The RheoMetal process (previously called the Rapid S- and RSF- process) is a novelmethod to produce cost effective, high quality, semisolid slurries for component casting. TheRheoMetal process uses an Enthalpy Exchange Material (EEM) as cooling agent to absorb heat andproduce a slurry. Critical process parameters to create a slurry by robust melting of the EEM arealloy content, stirring speed, EEM to melt ratio, EEM temperature, EEM microstructuralcharacteristics and melt superheat.In this paper, the melting sequence and melting rate of the EEM was studied experimentally. Theeffect of EEM composition, as well as superheat, on evolution of shape and dimension of the EEMduring stirring was investigated. Initial material freezing onto the EEM was observed, followed by astationary phase with subsequent gradual melting of the EEM. It was shown that the characteristicsof freeze-on layer were strongly correlated to melt superheat, EEM temperature, as well as materialcomposition, hence also has significant influence on the melting sequence.
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| 4. |
- Payandeh, Mostafa, 1981-, et al.
(författare)
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Influence of Microstructural Inhomogeneity on Fracture Behaviour in SSM-HPDC Al-Si-Cu-Fe Component with Low Si Content
- 2015
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Ingår i: Solid State Phenomena. - Switzerland : Trans Tech Publications Inc.. - 1012-0394 .- 1662-9779. ; 217-218, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- In the current paper, a low-Si aluminium alloy (1.4-2.4% Si) was used to fabricate acomplex shape telecom component using Semi-Solid High-Pressure Die Cast (SSM-HPDC),process. Microstructure and fracture characteristics were investigated. The cast material exhibitedmicrostructural inhomogeneity, in particular macrosegregation in the form of liquid surfacesegregation bands in addition to sub-surface pore bands and gross centre porosity. Tensilespecimens were taken from the cast components. Elongation and microstructural inhomogeneitywere investigated and correlated. Fracture surfaces of the tensile specimen were examined underscanning electron microscope (SEM). The study showed that both near surface liquid segregationbands and subsurface porosity strongly affected the fracture behaviour. Dominant for loss ofductility was gross centre porosity. The centre porosity was found to be a combination of trappedgas and insufficient, irregular feeding patterns.
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| 5. |
- Payandeh, Mostafa, 1981-, et al.
(författare)
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Mechanical And Thermal Properties Of Rheocast Telecom Component Using Low Silicon Aluminium Alloy In As-Cast And Heat-Treated Conditions
- 2015
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Ingår i: Light Metals 2015. - Hoboken, NJ : John Wiley & Sons. - 9781119082446 - 9781119093435
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Konferensbidrag (refereegranskat)abstract
- The growing demand for increasingly more cost and energy effective electronics components is a challenge for the manufacturing industry. To achieve higher thermal conductivity in telecom components, an aluminum alloy with a composition of Al-2Si-0.8Cu-0.8Fe-0.3Mn was created for rheocasting. Yield strength and thermal conductivity of the material were investigated in the as cast, T5 and T6 heat-treated conditions. The results showed that in the as-cast condition thermal conductivity of 168 W/mK and yield strength of 67 MPa was achieved at room temperature. A T5 treatment at 200°C and 250°C increased thermal conductivity to 174 W/mK and 182 W/mK, respectively, while only a slight increase in yield strength was observed. Moreover, a T6 treatment resulted in similar thermal conductivity as the T5 treatment at 250°C with no significant improvement in yield strength. Therefore, the T5 treatment at 250°C was suggested as an optimum condition for the current alloy composition.
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| 6. |
- Payandeh, Mostafa, 1981-, et al.
(författare)
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Solidification and re-melting phenomena during slurry preparation using the RheoMetal™ process
- 2017
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 48:6
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Tidskriftsartikel (refereegranskat)abstract
- The melting sequence of the enthalpy exchange material (EEM) and formation of a slurry in the RheoMetal™ process was investigated. The EEM was extracted and quenched, together with a portion of the slurry at different processing times before complete melting. The EEM initially increased in size/diameter due to melt freezing onto its surface, forming a freeze-on layer. The initial growth of this layer was followed by a period of a constant diameter of the EEM with subsequent melting and decrease of diameter. Microstructural characterization of the size and morphology of different phases in the EEM and in the freeze-on layer was made. Dendritic equiaxed grains and eutectic regions containing Si particles and Cu-bearing particles and Fe-rich particles were observed in the as-cast EEM. The freeze-on layer consisted of dendritic aluminum tilted by about 30 deg in the upstream direction, caused by the rotation of the EEM. Energy dispersion spectroscopy analysis showed that the freeze-on layer had a composition corresponding to an alloy with higher melting point than the EEM and thus shielding the EEM from the surrounding melt. Microstructural changes in the EEM showed that temperature rapidly increased to 768 K (495 °C), indicated by incipient melting of the lowest temperature melting eutectic in triple junction grain boundary regions with Al2Cu and Al5Mg8Si6Cu2 phases present. As the EEM temperature increased further the binary Al-Si eutectic started to melt to form a region of a fully developed coherent mushy state. Experimental results and a thermal model indicated that as the dendrites spheroidized near to the interface at the EEM/freeze-on layer reached a mushy state with 25 pct solid fraction, coherency was lost and disintegration of the freeze-on layer took place. Subsequently, in the absence of the shielding effect from the freeze-on Layer, the EEM continued to disintegrate with a coherency limit of a solid fraction estimated to be 50 pct.
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