Rolling Twin Roll Cast Magnesium Strips with Varied Temperature and Degree of Deformation

Abstract

Reducing vehicle weight and emissions by lightweight design is a major goal of the automotive industry. Magnesium as the lightest structural metal bears a significant weight saving potential compared to steels and aluminum. Cast magnesium components are widely used e.g. as engine blocks or gear box houses. The application of magnesium sheets is currently hampered by two main obstacles. The low formability of magnesium sheets requires a high number of rolling passes to roll cast slabs to final gauge which leads into a cost issue for the production of magnesium sheets. An alternative cost efficient production route for magnesium sheets with improved properties is the feedstock production by twin roll casting (TRC). In the twin roll casting process liquid metal is pumped from furnace or cast over a pipe into a tundish. The melt is then dragged into the roll gap of a pair of counter rotating, internally cooled rolls. The metal solidifies upon contact with the cooled rolls and gets rolled to a strip. This paper reports on results of rolling experiments on twin roll cast strips of magnesium alloy AZ31 (Mg-3Al-1Zn-Mn), which has been cast with different process conditions. The influence of the strip properties and the rolling process parameters like temperature and degree of deformation on the microstructure, the texture and the mechanical properties of the strip is presented and discussed. By future optimization of process parameters of twin roll casting and the subsequent rolling of the sheets, a serious challenge for conventional materials is within reach.

Twin-Roll Casting as a Grain Refinement Method and Its Influence on the Microstructure and Deformation Behavior of an AZ31 Magnesium Alloy Wire

“…In addition, twins can be observed for the AZ31 TRC, especially in the heat-treated state. In the case of the AZ31 strip, a weak basal texture after twin-roll casting was already reported [44]. After heat treatment, the texture is still present.…”

The Influence of Conventional or KOBO Extrusion Process on the Properties of AZ91 (MgAl9Zn1) Alloy

“…According to the literature data presented in [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 37 , 38 ], AZ91 (MgAl9Zn1) magnesium alloys are not only foundry materials. They were used during the implementation of conventional plastic working processes and severe plastic deformation (SPD) processes [ 6 , 7 , 8 , 9 , 10 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. However, in the case of the Equal-Channel Angular Pressing (ECAP), or High-Pressure Torsion (HPT) methods, the obtained samples were small, which meant that they could be used only for basic laboratory tests.…”

“…Currently, the best results have been obtained for the processes of co-extrusion of magnesium pipes with the use of mandrels, while as for the other methods of plastic working, the progress in the field of their forging and stamping is clearly noticeable. At the same time, innovative methods of rolling sheets of magnesium alloys [ 10 , 11 , 12 , 13 , 14 , 15 ] are being developed. For example, Kurz et al [ 10 ] presented the results of the casting experiments with the use of twin rolls of AZ31 (MgAl3Zn1) magnesium alloy tapes.…”

“…At the same time, innovative methods of rolling sheets of magnesium alloys [ 10 , 11 , 12 , 13 , 14 , 15 ] are being developed. For example, Kurz et al [ 10 ] presented the results of the casting experiments with the use of twin rolls of AZ31 (MgAl3Zn1) magnesium alloy tapes. Bergea et al [ 11 ] showed results of the influence of temperature on the mechanical properties of the twin-roll cast, rolled, and heat-treated AZ31 (MgAl3Zn1), investigated under tensile loading from different directions.…”

Microstructure Evolution and Mechanical Properties of Thin Strip Twin Roll Cast (TRC) Mg Sheet

“…The 5 mm TRC strip however has a maximum yield strength of 200 MPa parallel to the casting direction with the yield strength perpendicular to the casting direction reaching approximately 155 MPa. A yield strength of 240 MPa is generally reported for the TRC and hot rolled AZ31 strip using conventional TRC processes [11] which is achieved through the BCAST-TRC in the as-cast condition.…”