Apparatus for testing the size and the spacings of silicon crystals in Al-Si alloys

摘要

An apparatus for testing the size and the spacings of silicon crystals in Al-Si alloys comprises a housing; a horizontal guide accommodated in the housing, and a pointed scanning needle secured by a spring device to the horizontal guide with constant feed. The needle is arranged to scan a surface of a workpiece to be tested with a predetermined force and has applied thereto an electrical voltage which upon contacting an aluminum section of the workpiece transmits a voltage applied to the workpiece to a voltmeter, but partially or entirely interrupts same upon contacting a silicon crystal.