Density and thermal expansion of the aluminium alloy Al-17Si-4Cu (A390) in the solid and liquid states
E. Kaschnitz and R. Ebner
Density and thermal expansion of the aluminium alloy Al-17Si-4Cu (A390) were measured in the temperature range from room temperature to 740ºC using pushrod and piston dilatometry. Commercial pushrod dilatometers (NETZSCH DIL 402E and 402CD) were used for the measurements. The specimens are heated and cooled slowly at controlled rates in a furnace; the expansion is transferred by one or two long thin rods to displacement sensors. A graphite tubular body with two graphite pistons of just sufficient clearance was used to contain the specimen in the mushy region and in the liquid state.
During the growing of the primary silicon crystal network at solidification, the material does not shrink but expands slightly. Starting with the aluminium-silicon eutectic at the eutectic temperature, the density increases rapidly to its solid state behavior. The linear thermal expansion in the solid state shows no peculiarities, but is significantly lower than those of eutectic or hypoeutectic aluminium-silicon alloys.
Keywords: Aluminium alloy A390; Al-17Si-4Cu; density; liquid metal; piston dilatometry; pushrod dilatometry; thermal expansion.