Impact of Initial State during Calibre Rolling: Investigating Microstructure and Mechanical Properties of AZ80 Magnesium Alloy

Abstract

In order to investigate the effect of rolling on microstructure and mechanical properties of different initial states, cast and extruded magnesium alloy AZ80 bars were rolled in calibre. The microstructural characterization was done by light microscopy. As a result, the initial grain size of the cast AZ80 (66 μm) clearly differs from the extruded bar (13 μm). After 14 passes of hot rolling in calibre, a significant grain refining effect was achieved resulting in grain sizes of 5 μm for the cast and 3 μm for the extruded material. To investigate the mechanical properties in the initial and rolled state, tensile tests of both conditions were conducted at room temperature. Due to grain refining, the tensile strength (162 MPa) and the elongation (3 %) of cast AZ80 increased remarkably during 14 passes of calibre rolling (360 MPa and 19 %). The strengthening effect was also evident for the rolled extruded AZ80. However, the cast material exhibited cracks during calibre rolling due to its inexpedient microstructure for a high deformation calibre. On the contrary, the extruded AZ80 was easily deformable. This shows the clear impact of initial states on aspired end properties of processed materials. Future investigations will deal with developing a suitable calibration for cast AZ80.