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  • 1. Kappey, Jens
    et al.
    Schneider, Marc
    Svensson, Ingvar
    Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Sjölander, Emma
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Shahid, Akhtar
    Arnberg, Lars
    Microstructure, Defects and Properties in Aluminium Alloy Castings: Modelling and Simulation2010In: : Advanced methods for industrial engineering, 2010Conference paper (Other academic)
  • 2.
    Payandeh, Mostafa
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Sjölander, Emma
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Jarfors, Anders E.W
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Wessen, Magnus
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Mechanical And Thermal Properties Of Rheocast Telecom Component Using Low Silicon Aluminium Alloy In As-Cast And Heat-Treated Conditions2015In: Light Metals 2015 / [ed] Margaret Hyland, Hoboken, NJ: John Wiley & Sons, 2015Conference paper (Refereed)
    Abstract [en]

    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.

  • 3. Schneider, Marc
    et al.
    Schaefer, Wilfred
    Sjölander, Emma
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Svensson, Ingvar L.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Simulation of Microstructure and Mechanical Properties of Aluminum Components during Casting and Heat Treatment2012Conference paper (Other academic)
  • 4.
    Seifeddine, Salem
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Sjölander, Emma
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Bogdanoff, Toni
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    On the role of copper and cooling rates on the microstructure, defect formations and mechanical properties of Al-Si-Mg alloys2013In: Materials Sciences and Applications, ISSN 2153-117X, E-ISSN 2153-1188, Vol. 4, no 3, p. 171-178Article in journal (Refereed)
    Abstract [en]

    This paper aims to assess the role of Cu on Al-Si-Mg alloys, in a range of 0 - 5 wt%, qualitatively on microstructure, defect formation, in terms of porosity, and strength in the as-cast conditions. The ternary system of Al-Si-Mg, using the A356 alloy as a base material, were cast using the gradient solidification technique; applying three different solidification rates to produce directional solidified samples with a variety of microstructure coarsenesses. Microstructural observations reveal that as the Cu levels in the alloys are increased, the amounts of intermetallic compounds as well as the Cu concentration in the α-Al matrix are increased. Furthermore, the level of porosity is unaffected and the tensile strength is improved at the expense of ductility.

  • 5.
    Sjölander, Emma
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Heat treatment of Al-Si-Cu-Mg casting alloys2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 6.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Payandeh, Mostafa
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Jarfors, A. E. W.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Wessén, M.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Thermal conductivity of liquid cast and rheocast telecom component using Al-6Si-2Cu-Zn (Stenal Rheo 1) in as-cast and heat treated condition2015Report (Other academic)
    Abstract [en]

    The thermal conductivity of a rheocast telecom component produced using Al-6Si-2Cu-Zn alloy (Stenal Rheo 1) was investigated in the as-cast, T5 and T6 conditions. Conventionally liquid cast samples were produced in a permanent mold and used as a reference material. In the rheocast component in as-cast condition, a thermal conductivity of 153 W/mK at room temperature were 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 cast alloy exhibited a lower thermal conductivity and a higher hardness for all conditions compared to the as-rheocast component.The microstructure of rheocast component showed material consisted of relatively large α1-Al particles formed during the slurry fabrication process and fine α2-Al particles formed in the die cavity. The macrosegregation in the form of the different ration of the primary α1-Al particles to secondary α2-Al particles in different positions of the rheocast component was observed. The relation between microstructural characteristics and thermal diffusivity was investigated by determining the local thermal conductivity in the rheocast component and ration of α1-Al particles to α2-Al particles. The results revealed that samples from the regions of the component with a high amount of α1-Al particles had a higher thermal conductivity. WDS measurement results pointed to that Si and Cu concentration in the α1-Al particles contained lower concentrations value compare to the α2-Al particles and therefore α1-Al particles has higher value for 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. When the silicon is precipitated by heat treatment the thermal conductivity increases. For an optimal combination of thermal and mechanical properties it is therefore important to use an ageing temperature above the temperature for Si precipitation.

  • 7.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Artificial ageing of Al–Si–Cu–Mg casting alloys2011In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 528, no 24, p. 7402-7409Article in journal (Refereed)
    Abstract [en]

    The T6 heat treatment is commonly used for gravity cast Al-Si-Cu-Mg alloys. The influence of the alloying elements Cu and Mg and the artificial ageing temperature on the age hardening response were investigated. Artificial ageing was conducted at 170°C and 210°C for various times for three alloys, Al-7Si-0.3Mg, Al-8Si-3Cu and Al-8Si-3Cu-0.5Mg, cast with three different solidification rates (secondary dendrite arm spacing of about 10, 25 and 50μm). The coarseness of the microstructure has a small influence on the yield strength, as long as the solution treatment is adjusted to obtain complete dissolution and homogenisation. The peak yield strength of the Al-Si-Mg alloy is not as sensitive to the ageing temperature as the Al-Si-Cu and Al-Si-Cu-Mg alloys are. The ageing response of the Al-Si-Cu alloy is low and very slow. When 0.5 wt% Mg is added the ageing response increases drastically and a peak yield strength of 380 MPa is obtained after 20 h of ageing at 170°C for the finest microstructure, but the elongation to fracture is decreased to 3%. The elongation to fracture decreases with ageing time in the underaged condition as the yield strength increases for all three alloys. A recovery in elongation to fracture of the Al-Si-Cu-Mg alloy on overageing is obtained for the finest microstructure, while the elongation remains low for the coarser microstructures. The quality index, Q= YS +Kε, can be used to compare the quality of different Al-Si-Mg alloys. This is not true for Al-Si-Cu-Mg alloys, as K depends on the alloy composition. Overageing of the Al-Si-Mg alloy results in a decrease in quality compared to the underaged condition

  • 8.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Evaluating the plastic deformation of Al-Si-Cu-Mg casting alloys using the Hollomon and Ludwigson equations2011In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336Article in journal (Other academic)
    Abstract [en]

    The plastic part of true stress – true strain curves of three Al-Si casting alloys was evaluated using the Hollomon and Ludwigson equations. Three coarsenesses of the microstructure, two ageing temperatures and a number of ageing times were used. The Hollomon equation was able to describe the true stress – true strain curves for microstructures containing shearable precipitates, while the Ludwigson equation was needed for microstructures containing a supersaturated solid solution. A two bump shape appeared on the double logarithmic plot for the Al-Si-Cu alloy and the overaged Al-Si-Cu-Mg alloy. These curves could not be well described by the Hollomon or the Ludwigson equations.

  • 9.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Influence of alloy composition, solidification rate and artificial aging on plastic deformation behaviour of Al-Si-Cu-Mg casting alloys2013In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 26, no 1, p. 28-36Article in journal (Refereed)
    Abstract [en]

    The plastic deformation behaviour of three Al–Si casting alloys was investigated using the Kocks–Mecking strain hardening theory. Three coarsenesses of the microstructure, two aging temperatures and a number of aging times were used. For Al–Si–Mg and Al–Si–Cu–Mg alloys,the dislocation storage rate decreases while the dislocation recovery rate increases with agingtime during underaging, whereas the concentration of alloying elements in solid solution decreases. The storage rate reaches a minimum at the peak aged condition and increases at overaging. The storage and recovery rates of the Al–Si–Cu alloy increase with aging time in the underaged condition and start to decrease during overaging, which indicates that a mixture of shearable and non-shearable precipitates are present during underaging, whereas all precipitates become non-shearable on overaging.

  • 10.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Influence of natural ageing on the artificial ageing response of Al-Si casting alloys2012In: Conference on High Tech Die Casting: Innovation, Perspectives & Challenges in Pressure Die Casting of Light Alloys, 2012Conference paper (Other academic)
  • 11.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting. Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting. Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Optimisation of solution treatment of cast Al–Si–Cu alloys2010In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 31, no suppl. 1, p. 44-49Article in journal (Refereed)
    Abstract [en]

    The influence of solidification rate on the solution treatment response for an Al–8Si–3.1Cu alloy has been investigated. The alloy was cast using the gradient solidification technique to produce samples with three different solidification rates. The samples were solution treated at 495 C for various times between 10 min and 10 h. The concentration of copper in the matrix was measured using the wavelength dispersive spectroscopy technique, WDS.

    The results show that the coarseness of the microstructure clearly affects the solution treatment time needed to dissolve particles and obtain a homogenous distribution of copper in the matrix. A short solution treatment time of 10 min is enough to achieve a high and homogenous copper concentration for a material with a fine microstructure (secondary dendrite arm spacing, SDAS of 10 μm), while more than 10 h is needed for a coarse microstructure (SDAS of 50 μm). A model was developed to describe the dissolution and homogenisation process. The model shows good agreement with the experimental results.

  • 12.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Optimization of solution treatment of cast Al-7Si-0.3Mg and Al-8Si-3Cu-0.5Mg alloys2014In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 45, no 4, p. 1916-1927Article in journal (Refereed)
    Abstract [en]

    The influence of solidification rate on the solution-treatment response has been investigated for an Al-7Si-0.3Mg alloy and an Al-8Si-3Cu-0.5Mg alloy. The concentrations of Mg, Cu, and Si in the matrix after different solution-treatment times were measured using a wavelength dispersive spectrometer. All Mg dissolves into the matrix for the Al-Si-Mg alloy when solution treated at 803 K (530 C) because the π-Fe phase is unstable and transforms into short β-Fe plates which release Mg. The Q-Al5Mg8Cu2Si6 phase do not dissolve completely at 768 K (495 C) in the Al-Si-Cu-Mg alloy and the concentration in the matrix reached 0.22 to 0.25 wt pct Mg. The distance between π-Fe phases and Al2Cu phases was found to determine the solution-treatment time needed for dissolution and homogenization for the Al-Si-Mg alloy and Al-Si-Cu-Mg alloy, respectively. From the distance between the phases, a dimensionless diffusion time was calculated which can be used to estimate the solution-treatment times needed for different coarsenesses of the microstructure. A model was developed to describe the dissolution and homogenization processes.

  • 13.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting. Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting. Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    The heat treatment of Al–Si–Cu–Mg casting alloys2010In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 210, no 10, p. 1249-1259Article in journal (Refereed)
    Abstract [en]

    Heat treatment of gravity cast aluminium components normally involve a solution heat treatment followed by quenching and subsequent ageing, either naturally or artificially. The mechanical properties of aluminium castings containing Cu and Mg are clearly improved by heat treatment but there are still some uncertainties and contradictions about the phase dissolution, formation of precipitates and the influence of natural and artificial ageing parameters such as time and temperature, on the peak strength of these materials. The present paper reviews over 60 papers in attempt to clarify and map out the influence of each and every sequence that is involved in the heat treatment process on the evolution and kind of precipitates, which in turn determines the mechanical properties of cast aluminium components.

  • 14.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    The influence of natural ageing on the artificial ageing response of Al-Si-Cu-Mg casting alloys2012In: La Metallurgia Italiana, ISSN 0026-0843, Vol. 11-12, p. 39-43Article in journal (Refereed)
    Abstract [en]

    The T6 heat treatment is commonly used to increase the strength of gravity cast Al-Si components containing Cu and/or Mg. The artificial ageing response is known to be affected by the thermal history, such as solution treatment, quench rate, natural ageing and heating rate to the artificial ageing temperature. The influence of natural ageing on the artificial ageing response was investigated for three alloys; Al-8Si-0.4Mg, Al-7Si-3Cu and Al-8Si-3Cu-0.4Mg. Natural ageing had a strong influence on the ageing response of the Al-Si-Mg alloy in the underaged condition and the strength increase was strongly reduced. Despite this, the time to peak yield strength as well as its magnitude were not strongly affected by natural ageing. No clear influence of natural ageing was observed for the Al-Si-Cu alloy. For the Al-Si-Cu-Mg alloy the ageing response seems to depend on the natural ageing time. Natural ageing of 3 weeks shifted the peak yield strength to shorter ageing times and its magnitude was decreased a little compared to direct ageing after quench. Natural ageing of 1 day gave the least beneficial properties after artificial ageing.

  • 15.
    Sjölander, Emma
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Svensson, Ingvar
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Modelling yield strength of heat treated Al–Si–Mg casting alloys2011In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 24, no 6, p. 338-346Article in journal (Refereed)
    Abstract [en]

    A model for the yield strength of artificially aged Al–Si–Mg casting alloys has been developed. The model includes Mg concentrations between 0.2 and 0.6 wt-% and aging temperatures between 150°C and 210°C. Spherical precipitates with the composition Mg5Si6, which grow by diffusion of Mg from the surrounding α-Al matrix, are assumed in the model. Nucleation is assumed to be instantaneous and growth of the precipitates is modelled using Fick’s second law and mass balance. When supersaturation is lost the continued precipitate growth is modelled using the Lifshitz–Slyozov–Wagner coarsening law. An average precipitate radius is calculated and a precipitate size distribution is introduced by using a relation between the average radius and its standard deviation. The strength contribution from precipitates is calculated using coherency strengthening and Orowan strengthening. The agreement between the model and experimental data is generally good; however, modelling the underaged condition needs further refinement.

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