Thermal conductivity of liquid cast and rheocast telecom component using Al-6Si-2Cu-Zn (Stenal Rheo 1) in as-cast and heat treated condition
2015 (English)Report (Other academic)
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. ,  p.
JTH research report, ISSN 1404-0018 ; 2015-01
Thermal conductivity, Microstructure characteristics, Stenal Rheo1 alloy, Rheo-casting, High pressure die-casting
Engineering and Technology
IdentifiersURN: urn:nbn:se:hj:diva-26296OAI: oai:DiVA.org:hj-26296DiVA: diva2:799290
FunderKnowledge Foundation, 20100203