Forming limit diagrams of twin-roll cast, rolled and heat-treated AZ31 as a function of temperature and loading rate

Sheet metal forming experiments have been carried out on AZ31 and ZE10 sheets produced by rolling conventionally DC cast slabs as well as twin roll cast (TRC) strips. Nakajima tests were performed on the various sheet materials over the temperature range from RT to 200 °C using Hasek type samples of specified geometries to generate various strain paths. The strain path data were used to derive the forming limit curves as plotted in forming limit diagrams for the two alloys. The temperature dependence of the sheet formability is discussed in terms of the operating deformation mechanisms and the roles of alloy composition, initial texture and processing history.

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Influence of the Sheet Manufacturing Process on the Forming Limit Behaviour of Twin-Roll Cast, Rolled and Heat-Treated AZ31

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.746.154 ◽

2017 ◽

Vol 746 ◽

pp. 154-160 ◽

Cited By ~ 3

Author(s):

Thorsten Henseler ◽

Madlen Ullmann ◽

Rudolf Kawalla ◽

Franz Berge

Keyword(s):

Sheet Metal ◽

Elevated Temperatures ◽

Lightweight Design ◽

Sheet Thickness ◽

Forming Limit ◽

Specific Strength ◽

Heat Treated ◽

Limit Behaviour ◽

Twin Roll Cast ◽

Twin Roll

In the age of lightweight design, magnesium alloys play an increasing role in weight reduction of transport vehicles. The specific strength compared to aluminium alloys and steel grades is superior, giving the material great potential in lightweight application. The automobile and aeronautic industry use sheet metals with minimum thicknesses, making research in this field very important. Successful sheet metal forming depends on various process parameters and material characteristics. Thus, the influence of sheet thickness on the forming limit behaviour of twin-roll cast, rolled and heat-treated AZ31 was investigated. Nakajima tests were performed on a hydraulic sheet metal testing device at elevated temperatures with various sheet thicknesses from 0.6 mm to 2.0 mm. The results show an increase in formability with rising temperatures for all sheets. Furthermore, changes in formability among the sheet thicknesses were linked to their divergent microstructures, which result from the different sheet manufacturing parameters.

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The Effect of Sheet Thickness, Loading Rate and Punch Diameter on the Deformation Behaviour of AZ31 during 3-Point Bending

Materials Science Forum ◽

10.4028/www.scientific.net/msf.854.65 ◽

2016 ◽

Vol 854 ◽

pp. 65-72

Author(s):

Franz Berge ◽

Heiko Winderlich ◽

Christina Krbetschek ◽

Madlen Ullmann ◽

Rudolf Kawalla

Keyword(s):

Loading Rate ◽

Deformation Behaviour ◽

Testing Machine ◽

Sheet Thickness ◽

Bending Test ◽

Bending Angle ◽

Grain Sizes ◽

Heat Treated ◽

Twin Roll Cast ◽

Twin Roll

In this study, the influence of sheet thickness, loading rate, and punch diameter on the bending behaviour of twin-roll cast, rolled and heat-treated AZ31 magnesium alloy was investigated. Therefore, the 3-point bending test was performed at room temperature using an electromechanical testing machine (v = 0.1−10 mm/s) with different punch diameters (D = 2 mm, 8 mm, 16 mm). The initial material has a recrystallized microstructure with grain sizes of 6−9 µm. It is shown by the mechanical investigations that the bending force increases with the sheet thickness. In contrast to this, the bending angle is independent of the sheet thickness. In addition, the punch diameter and the loading rate do not influence the maximum force and the bending angle significantly.

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Improving Mechanical Properties of Twin-Roll Cast AZ31 by Wire Rolling

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1016.957 ◽

2021 ◽

Vol 1016 ◽

pp. 957-963

Author(s):

Marie Moses ◽

Madlen Ullmann ◽

Rudolf Kawalla ◽

Ulrich Prahl

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Rolling Texture ◽

Total Elongation ◽

Roll Casting ◽

Heat Treated ◽

Heat Treated Condition ◽

Set Up ◽

Twin Roll Cast ◽

Twin Roll

Since 2018, the institute of metal forming has been studying the novel twin-roll casting (TRC) of magnesium wire at the pilot research plant set up specifically for this purpose. Light microscopic and scanning electronic investigations were carried out within this work and show the unique microstructure of twin-roll cast AZ31 magnesium alloy with grain sizes of about 10 μm ± 4 μm in centre and 39 μm ± 26 μm near the surface of the sample. By means of a short heat treatment (460 °C/15 min), segregations can be dissolved and grain size changes in centre to 19 μm ± 12 μm (increase) and near the surface to 12 μm ± 7 μm (decrease). Further, the mechanical properties of the twin-roll cast and heat-treated wire were analysed by tensile testing at room temperature. By heat treatment, the total elongation could be increased by a third whereas the strength decreases slightly. In heat-treated state, no preferred orientation is evident. In addition to the twin-roll cast and the heat-treated condition, the rolled state was analysed. For this purpose, the twin-roll cast wire was hot rolled using an oval-square calibration. After hot rolling, a dynamic recrystallization and grain refinement of the twin-roll cast wire could be achieved. It can be seen, that an increase in strength as well as in total elongation occur after wire rolling. Beside this, a rolling texture is evident.

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Influence of the Processing of Magnesium Alloys AZ31 and ZE10 on the Sheet Formability at Elevated Temperature

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.473.335 ◽

2011 ◽

Vol 473 ◽

pp. 335-342 ◽

Cited By ~ 20

Author(s):

Lennart Stutz ◽

Jan Bohlen ◽

Gerrit Kurz ◽

Dietmar Letzig ◽

Karl Ulrich Kainer

Keyword(s):

Elevated Temperatures ◽

Plastic Anisotropy ◽

Production Costs ◽

Processing Route ◽

Forming Limit ◽

Rolled Sheet ◽

Strain Paths ◽

Twin Roll Cast ◽

Hot Rolled ◽

Twin Roll

The substitution of conventional materials such as aluminium alloys and steels with the lightest structural metal magnesium and its alloys can yield significant weight saving in the transportation industry and hence, reduce vehicle weight and greenhouse gas emissions. Producing magnesium sheets by conventional hot rolling is expensive due to the large number of rolling passes to final gauge and annealing steps at elevated temperatures between the rolling passes. Twin roll casting is a well established processing route for aluminium sheets which can reduce the necessary rolling passes to a bare minimum to reduce the production costs. This process is receiving increasing attention for the production of magnesium sheets. This study reveals first hand results of sheet metal forming experiments on magnesium sheets rolled from twin roll cast strip as well as conventional DC cast slabs. Two different alloys, AZ31 (Mg-3Al-1Zn-Mn) and rare earth element containing ZE10 (Mg-1Zn-RE) were investigated. It is known that these alloys show significant differences in the microstructure development during conventional rolling as a result of recrystallisation. For hot rolled AZ31, distinct textures are formed with the majority of basal planes oriented in the sheet plane and hence, unfavourably for basal slip. Conventionally rolled ZE10 commonly shows a much weaker texture. Forming limit diagrams are presented and discussed with respect to the initial texture of the sheets. Strain response to various strain paths and plastic anisotropy are evaluated. Results of twin roll cast sheets are compared with conventionally hot rolled sheet of the same alloys. Competitive formability can be achieved at 200°C for all tested sheets. While conventionally rolled sheets show a generally higher formability than their twin roll cast counterparts, ZE10 outperforms AZ31 for both processing routes.

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Influence of Temperature, Strain Rate, and Sheet Thickness on the Deformation Behaviour of Twin-Roll Cast, Rolled and Heat-Treated AZ31 under Uniaxial Loading

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.684.29 ◽

2016 ◽

Vol 684 ◽

pp. 29-34

Author(s):

Franz Berge ◽

Markus Wollschläger ◽

Christina Krbetschek ◽

Madlen Ullmann

Keyword(s):

Flow Stress ◽

Strain Rate ◽

Deformation Behaviour ◽

Sheet Thickness ◽

Influence Of Temperature ◽

Heat Treated ◽

Elongation To Failure ◽

Twin Roll Cast ◽

Twin Roll ◽

Temperature Strain

The influence of temperature, strain rate, and sheet thickness on the mechanical properties of twin-roll cast, rolled and heat-treated AZ31 was investigated under tensile loading from different directions (0°, 90°). To assess the forming behaviour of different sheet thicknesses (0.6 mm, 1 mm), tensile tests were performed with an electromechanical testing device between 20 °C and 300 °C at strain rates of 10−4 s−1 and 10−2 s−1. With rising temperature, the flow stress decreased while the elongation to failure (A80) increased, which may be related to the enhanced dislocation motion and the activation of additional nonbasal slip systems at T > 200 °C. It can be seen that the anisotropy of flow stress and elongation to failure was influenced by the temperature, the strain rate, and the sheet thickness.

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