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Thermal conductivity of liquid cast and rheocast telecom component using Al-6Si-2Cu-Zn (Stenal Rheo 1) in as-cast and heat treated condition
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.ORCID iD: 0000-0001-6755-2123
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.ORCID iD: 0000-0002-0101-0062
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
2015 (English)Report (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.

Place, publisher, year, edition, pages
Jönköping: Jönköping University, School of Engineering , 2015. , [19] p.
Series
JTH research report, ISSN 1404-0018 ; 2015-01
Keyword [en]
Thermal conductivity, Microstructure characteristics, Stenal Rheo1 alloy, Rheo-casting, High pressure die-casting
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:hj:diva-26296OAI: oai:DiVA.org:hj-26296DiVA: diva2:799290
Funder
Knowledge Foundation, 20100203
Available from: 2015-03-30 Created: 2015-03-30 Last updated: 2016-08-12Bibliographically approved
In thesis
1. Rheocasting of Aluminium Alloys: Slurry Formation, Microstructure, and Properties
Open this publication in new window or tab >>Rheocasting of Aluminium Alloys: Slurry Formation, Microstructure, and Properties
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Innovative materials with novel properties are in great demand for use in the criticalcomponents of emerging technologies, which promise to be more cost-effective and energyefficient.A controversial issue with regard to manufacturing complex industrial products isto develop advanced materials with optimised manufacturability in addition to the requiredmechanical and physical properties. The objective of this research study was to develop andoffer new solutions in material-processing-related issues in the field of mechanical andelectrical engineering. This was achieved by investigating the new opportunities affordedby a recently developed rheocasting method, RheoMetalTM process, with the goal of comingto an understanding of the critical factors for effective manufacturing process.

A study of the evolution of microstructure at different stages of the rheocasting process,demonstrated the influence of multistage solidification on the microstructural characteristicsof the rheocast components. The microstructural investigation onquench slurry showed itconsists of the solute-lean coarse globular α-Al particles with uniform distribution ofalloying elements, suspended in the solute-rich liquid matrix. Such inhomogeneous slurryin the sleeve seems to play a critical role in the inhomogeneity of final microstructure. Inthe rheocast component, the separation of the liquid and solid parts of slurry during fillinginfluenced on the microstructural inhomogeneity.

The relationship between the microstructural characteristics and properties of the rheocastcomponents was investigated. The study on the fracture surfaces of the tensile-testedspecimens showed that the mechanical properties strongly affected by microstructuralinhomogeneity, in particular macrosegregation in the form of near surface liquid segregationbands and subsurface porosity. The thermal conductivity measurement showed variation ofthis property throughout the rheocast component due to variations in the ratio of solute-leanglobular α-Al particles and fine solute α-Al particles. The result showed silicon in solidsolution have a strong influence (negative) on thermal conductivity and precipitation ofsilicon by heat treatment process increase the thermal conductivity.

Place, publisher, year, edition, pages
Jönköping: Jönköping University, School of Engineering, 2015. 50 p.
Series
JTH Dissertation Series, 6
Keyword
SSM Casting, aluminium alloy, RheoMetalTM process, microstructure, physical and mechanical properties
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-26297 (URN)978-91-87289-07-1 (ISBN)
Presentation
2015-04-24, E1405, Tekniska Högskolan, Högskolan i Jönköping, Jönköping, 14:36 (English)
Opponent
Supervisors
Projects
RheoCom
Funder
Knowledge Foundation, 20100203
Available from: 2015-04-08 Created: 2015-03-30 Last updated: 2016-08-12Bibliographically approved

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