Microstructure and texture studies on twin-roll cast AZ31 (Mg–3wt.%Al–1wt.%Zn) alloy and the effect of thermomechanical processing

Magnesium Sheet; Challenges and Opportunities

“…These observations indicate the advantage of the rapid cooling associated with the twin-roll casting process; generating a large fraction and uniform distribution of fine secondary-phase particles. Preliminary evaluation of mechanical properties at room temperature also proved the beneficial effect of such texture alteration, as compared to the as-twin-roll cast AZ31 sheet (Masoumi et al, 2010a). Fig.…”

“…These samples have been rolled down to 0.5-0.6 mm gauges, using a novel finish-rolling schedule developed specifically for cast magnesium alloy sheet (Liang & Cowley, 2004). Near-rapid solidification achieved in twin-roll casting, through cooling rates ranging from 300 to several thousands of degrees per second, can potentially improve alloy properties by improving the homogeneity of microstructures (especially minimizing the size of manganese-rich particles), refining grain size, reducing segregation, increasing solid solubility, enhancing precipitate nucleation within the matrix, and generating a distribution of fine precipitates (CSIRO, 2003& Masoumi et al, 2010a. The microstructure of a twin-roll cast AZ31 alloy, with about 5 mm thickness, consists of a columnar-grain zone from the surface to the mid-thickness region and an equiaxed-grain zone in the mid-thickness region.…”

Effect of melt conditioning on heat treatment and mechanical properties of AZ31 alloy strips produced by twin roll casting

“…, and the undercooling for nucleation is taken as TN = 0.5 K [13]. Also shown in Fig 7(b) are the experimentally estimated growth velocity and temperature gradient for MC-TRC of AZ31 alloy, which is a physical approach to grain refinement as will be discussed in this paper later.…”

“…Mg-alloy melts inevitably contain oxides, which normally exist in alloy melts in the form of composite films containing densely populated nanometre-scale MgO particles in a liquid matrix [11]. It is found that MC provided by the twin screw mechanism [11] can effectively disperse such oxide films into discrete MgO particles, giving rise to an increase of MgO number density by three orders of magnitude [13]. It has been confirmed that MgO does nucleate α-Mg during solidification of Mg-alloys [11].…”

“…Several attempts has been made by various researchers to improve the strength and formability of wrought magnesium by sequential warm rolling [12], thermo-mechanical process [13] and hot rolling [14] processes.…”