Electrical Resistivity of Al-Cast Alloys in the Range of Solidification

Abstract

The aim of this paper is to explain the electrical resistivity change during solidification and connect it with the thermal analysis and solidification course. The problem at conducting the “in situ” measurement by four-point technique is the electrode material, which often oxidizes during measurements causing high contact resistance and providing incorrect results. Various materials were tested and aluminum electrodes chosen. The advantage of aluminum electrodes is that they melt within the specimen immediately after being poured and cause no interface resulting with any contact resistance. Pure aluminum, hypoeutectic alloy AlSi7Mg, and eutectic AlSi12 alloys were tested. Resistivity of Al–Si alloys is increasing with Si content. Grain refinement and modification of βSi were employed. Grain refinement has any effect on electrical resistivity. Modification of βSi phase causes decrease of electrical resistivity. The electrical resistivity curves give information similar as cooling curves from thermal analysis measurements.