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.
Highlights
Of all construction metals, magnesium has the lowest density with a high specific strength and is a promising material to reduce the weight of components
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 in the scanning electron microscope (SEM) and can be found at 555 °C
Summary
Magnesium has the lowest density with a high specific strength and is a promising material to reduce the weight of components. Other influencing factors are technological parameters for example the amount of heat input and the cooling rate [4] Another criterion for assessing the hot cracking susceptibility of an alloy is the temperature range between NST and NDT. According to [11], the probability of the formation of hot cracks is strongly reduced if this range is less than 20 K. This temperature range and the HTBR are to be determined for twin-roll cast AZ31 magnesium alloy in this paper
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