Research Project MagPlast

The research project "Multi-axial plasticity in textured magnesium structures" is funded by the German Research Foundation (DFG) and the Fund for Scientific Research, Austria (FWF) within the funding program D-A-CH (project number 438040004). The international funding program enables the application of cross-border research projects between Germany, Austria and Switzerland. DFG - GEPRIS Link...

Magnesium alloys are becoming increasingly important for lightweight structures and associated material and energy savings due to their high specific static and cyclic strengths, high availability and economical production. However, the hexagonal crystal system and basal texture of cast-rolled magnesium fines results in complex deformation behavior that has not yet been adequately explored.

Recent studies on textured wrought Mg alloys under static and cyclic uniaxial loading as well as bending stresses show that highly localized strain fields result due to the grouping of twins occurring in the compression region. These so-called macroscopic bands of twinned grains, in which the compressive strain is many times higher than outside, have a great influence on the mechanical behavior. Current phenomenological material laws cannot represent these discontinuous strain fields. In addition, due to the complexity of biaxial compression tests, there is a lack of experimental data for characterizing the yield surface in the biaxial compressive stress range.

Mechanical testing and microstructural analysis of cast-rolled AZ31B will be used to explore the relationships between microstructural deformation mechanisms and macroscopic yielding and fatigue behavior under multi-axial loading. This should significantly increase the understanding of the mechanical behavior of magnesium and allow the elastoplastic deformation behavior of both currently used in industry and newly developed Mg alloys to be modeled.

Experiments include biaxial quasi-static and cyclic tests, in-situ uniaxial and biaxial scanning electron microscope (SEM) compression tests, and indentation tests. Microstructure is characterized by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) measurements. Emphasis is placed on initiation, growth and distribution of twins and their interaction with other defects such as grain boundaries and precipitates.

Based on these complementary investigations, the total yield surface for the wrought Mg alloy is established and the strain hardening behavior is characterized. The results will be used to develop an elastoplastic constitutive law for FEM simulations to calculate stress and strain fields and to develop a fatigue model for cyclic biaxial loading.

Dr. Whitmore is a specialist in microstructural analysis and testing. He works at Paris Lodron University Salzburg (PLUS) and will use the new TEM facility. The development and execution of the biaxial tests as well as the numerical modeling of the elastoplastic material behavior will be carried out at the Competence Center Lightweight Structures at Landshut University of Applied Sciences (LLK) by Mr. Nischler and Prof. Huber. Prof. Huber is a recognized researcher in the fields of materials modeling and lightweight design and heads the Lightweight Design Competence Center at Landshut University of Applied Sciences.  As a proven materials scientist, Prof. Saage (LLK) supports the research project in the field of materials analysis.