Abstract. The knowledge of the formation of hot cracks in magnesium alloys is fundamental for good quality in the production and further processing of the strips. Whether an alloy is susceptible to hot cracking and into which temperature range, can be taken into account during production and further processing. As a result, production rejects due to hot cracking can be minimized. Affected production steps can be casting, continuous casting, twin-roll casting, rolling or welding. 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 can be found at 555 °C. The HTBR shows a range 35 K.
Formation of hot cracks in alloys is a critical issue for their production and processing. In this study, the susceptibility of the cast Mg97Y2Zn1 alloy containing long period stacking ordered (LPSO) structures to hot cracking was investigated using tensile tests in a Gleeble testing machine, and described in terms of the brittle temperature range (BTR), which was concluded from the zero strength temperature (ZST), zero ductility temperature, and ductility recovery temperature (DRT). The zero ductility and the DRTs were obtained directly from the mechanical tests, verified using fracture surface analysis in a scanning electron microscope, and correlated with the solidification range that was determined using differential scanning calorimetry. The extent of the BTR was 31 K, the width of the solidification range 100 K. The ZST coincided with the dissolution temperature of the LPSO structures, which means that the hot cracking susceptibility of the cast Mg97Y2Zn1 alloy is dominated by the dissolution of LPSO structures.
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