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

2017 ◽  
Vol 746 ◽  
pp. 154-160 ◽  
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.

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

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.

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

2011 ◽  
Vol 473 ◽  
pp. 335-342 ◽  
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.

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

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.

Magnesium Sheet Metal Forming Considering its Specific Yield Behavior

2005 ◽  
Vol 6-8 ◽  
pp. 771-778 ◽  
Author(s):  
M. Redecker ◽  
Karl Roll ◽  
S. Häussinger
Keyword(s):  
Sheet Metal ◽  
Elevated Temperatures ◽  
Flow Behavior ◽  
Specific Yield ◽  
Forming Limit ◽  
Forming Process ◽  
Local Flow ◽  
Yield Behavior ◽  
Magnesium Sheet ◽  
Testing Procedures

In recent years very strong efforts have been undertaken to build light weight structures of car bodies in the automotive industry. Structural technologies like Space Frame, tailored blanks and relief-embossed panels are well-known and already in use. Beside that there is a large assortment of design materials with low density or high strength. Magnesium alloys are lighter by approximately 34 percent than aluminum alloys and are considered to be the lightest metallic design material. However forming processes of magnesium sheet metal are difficult due to its complex plasticity behavior. Strain rate sensitivity, asymmetric and softening yield behavior of magnesium are leading to a complex description of the forming process. Asymmetric yield behavior means different yield stress depending on tensile or compressive loading. It is well-known that elevated temperatures around 200°C improve the local flow behavior of magnesium. Experiments show that in this way the forming limit curves can be considerably increased. So far the simulation of the forming process including temperature, strain rates and plastic asymmetry is not state-of-the-art. Moreover, neither reliable material data nor standardized testing procedures are available. According to the great attractiveness of magnesium sheet metal parts there is a serious need for a reliable modeling of the virtual process chain including the specification of required mechanical properties. An existing series geometry which already can be made of magnesium at elevated temperatures is calculated using the finite element method. The results clarify the failings of standard calculation methods and show potentials of its improvement.

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

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.

Methodology to Produce Locally Heat-Treated EN AW-5182 Aluminum Alloy Sheet Metal Parts

2012 ◽  
Vol 504-506 ◽  
pp. 113-118 ◽  
Author(s):  
Andreas Magnus Sulzberger ◽  
Marion Merklein ◽  
Wolfgang Staufner ◽  
Daniel Wortberg
Keyword(s):  
Sheet Metal ◽  
Material Flow ◽  
Sheet Thickness ◽  
Alloy Sheet ◽  
Second Step ◽  
Material Failure ◽  
Metal Parts ◽  
Sheet Metal Parts ◽  
Material Recovery ◽  
Heat Treated

Compared to steel, aluminum has a reduced formability. The consequence is that the drawability of aluminum needs to be extended. This can be achieved by a material recovery that takes place near the zones in which a material failure is initiated during deep drawing. In the considered process, first the aluminum component will be preformed to a specific stress state. In the second step, it will be partial heat treated, before the component is getting finished. Based on the selective intermediate introduction of heat, the material flow of the pre-drawn part is influenced in such a manner that the most highly stressed zones are subjected to further reduction in sheet thickness. This is possible by sacrificing material out of zones near the crack. These areas are referred to below as “sacrificial zones”. They depend on the position of the critical region as a result of the material pre-strain. In these regions, the temperature can be varied. This paper focuses on the development of a methodology to determine a layout of intermediate heat treatment of preformed aluminum sheet metal components. In order to determine such a layout, a principal part must be designed on which the methodology can be reviewed.

scholarly journals Investigation of diffusion behavior of carburized sheet metal in hot stamping

2018 ◽  
Vol 190 ◽  
pp. 08004 ◽  
Author(s):  
Alexander Horn ◽  
Marion Merklein
Keyword(s):  
Mechanical Properties ◽  
Transition Zone ◽  
Sheet Metal ◽  
Lightweight Design ◽  
Hot Stamping ◽  
Sheet Thickness ◽  
Carbon Diffusion ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Body Parts

Today’s manufacturing of structural car body parts faces several challenges, like forming accuracy and passenger safety. Besides these two requirements, lightweight design plays an important role. One possibility to fulfill these partially rivalling demands is the application of hot stamped parts. The combination of hot forming and in die quenching reduces not only springback, but also results in tensile strengths of up to 1500 MPa. This makes a simultaneous reduction of sheet thickness and therefore weight reduction possible. Further development enabled a tailored adjustment of mechanical properties, for example by applying different cooling conditions along the parts. One of the biggest issues of these state of the art processes is the formation of a transition zone due to heat transfer. A promising approach to adjust the mechanical properties with a minimized transition zone is the carburization of sheet metal. Therefore, the parts are coated with graphite, heat treated and subsequently quenched. In this work, the time variant process of carbon diffusion is investigated. Sheets with two different thicknesses are carburized and quenched. The resulting mechanical properties are analyzed using uniaxial tensile tests and microhardness measurements. The results are correlated with the carbon content measured by EDX-analysis.

Influence of Temperature and Loading Rate on the Forming Limit Behaviour of Twin-Roll Cast, Rolled and Heat-Treated AZ31 as a Function of the Stress State

2016 ◽  
Vol 684 ◽  
pp. 67-73 ◽  
Author(s):  
Franz Berge ◽  
Thorsten Henseler ◽  
Christina Krbetschek ◽  
Madlen Ullmann ◽  
Rudolf Kawalla
Keyword(s):  
Stress State ◽  
Loading Rate ◽  
Sheet Thickness ◽  
Forming Limit ◽  
Limit Values ◽  
Loading Rates ◽  
Economic Production ◽  
Az31 Sheet ◽  
Limit Behaviour ◽  
Stress States

Magnesium and its alloys have high potential for lightweight applications in the automotive and aerospace industries. In order to design parts for new applications with optimized mechanical properties and higher, more economic production rates, the forming limit behaviour of thin sheets (t < 1.0 mm) has to be known for different temperatures and loading rates. In this study, forming limit curves of 0.8 mm thick AZ31 sheet were measured for deformation at 200 °C and 250 °C and at loading rates of 1 mm/s and 10 mm/s with the Nakajima test. The investigations showed that an increase in temperature from 200 °C to 250 °C tends toward higher forming limit values for all stress states. In contrast, an increase in the loading rate from 1 mm/s to 10 mm/s induces a reduction in formability. It can be seen that the temperature, loading rate, and stress state influence the force-distance curves, the distribution of the local major strains, and the sheet thickness reduction.

Effects of Processing, Texture and Temperature on the Formability of AZ31 and ZE10 Sheets

2011 ◽  
Vol 690 ◽  
pp. 298-301 ◽  
Author(s):  
Dietmar Letzig ◽  
Lennart Stutz ◽  
Jan Bohlen ◽  
Karl Ulrich Kainer
Keyword(s):  
Metal Forming ◽  
Alloy Composition ◽  
Deformation Mechanisms ◽  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Sheet Formability ◽  
Strain Paths ◽  
Twin Roll Cast ◽  
Twin Roll ◽  
Forming Limit Curves

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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