Determination of the Hot Cracking Tendency of a Twin-Roll Cast AZ31 Magnesium Alloy by Means of Gleeble Tests

Abstract

The knowledge about the formation of hot cracking in magnesium alloys, such as in twin-roll cast magnesium sheets and strips, is fundamental for a good quality of the strips during the further processing by rolling or welding and minimize the reject. Hot cracking often occurs in the so-called mushy zone, when solid phases and melt coexist, at temperatures where the material no longer exhibits ductility. For the evaluation of the hot cracking tendency of an alloy, the width of the HTBR (High-temperature brittleness range) can be used. On the basis of a test on a Gleeble HDS-V40, the HTBR was determined for a twin-roll cast AZ31 magnesium alloy. The transition between ductile forming behaviour and complete brittle reaction of the AZ31 alloy is confirmed by the observation of the fracture surfaces (determination of the fracture type) in the scanning electron microscope (SEM) and is located at 555 °C. The HTBR shows a range 35 K.