Abstract
In the recent past, several researchers have successfully modeled the complex fatigue behavior of planar twin-roll cast AZ31B alloy sheets. Complex components are usually hot-bent, whereby the microstructure in the hot-bent areas changes significantly. However, studies on the fatigue behavior of hot-bent magnesium alloys are currently lacking. Therefore, a novel, uniaxial hot-bent specimen was developed and optimized with finite element method simulations. Microstructural analyses with the electron backscatter diffraction method reveal that the hot-bending process changes the texture and increases the Schmid factor for basal slip in rolling and transverse direction of the sheet. In the subsequent quasi-static tension and compression tests, anisotropic and asymmetric yield stresses, lower Young’s moduli compared with the as-received material and macroscopic bands of twinned grains are obtained. Finally, the study proves that the recently proposed concept of highly strained volume can accurately estimate the lifetime, even by combining the as-received and hot-bent material in one fatigue model.
Highlights
Innovative lightweight materials such as twin-rolled cast magnesium alloys will become considerably more important to reduce CO2 emissions in the future [1,2]
In order to address this aspect in a fatigue model, the concept of highly strained volume (CHεV) was proposed and applied to uniaxial unnotched, uniaxial notched, and bending specimens fabricated from a 3 mm-thick planar twin-roll cast AZ31B magnesium alloy sheet [16,19]
The c-axes become inclined from normal direction (ND) towards transverse direction (TD), which is more pronounced on the compression layer compared with the tension layer due to two effects
Summary
Innovative lightweight materials such as twin-rolled cast magnesium alloys will become considerably more important to reduce CO2 emissions in the future [1,2]. Fatigue modeling considering the mentioned aspects has been successfully performed on planar twin-roll cast magnesium (Mg) alloy sheets [10,11,12,13] and on hot-extruded Mg alloys [9,14,15]. It was found in [16,17,18,19] that a compressive stress parallel to the rolling or transverse direction of the sheet leads to macroscopic bands of twinned grains (BTGs). The fatigue behavior of the hot-bent material was modeled using the CHεV to demonstrate its applicability to hot-bent Mg-components
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