Tests and Finite Element Simulation of Yield Anisotropy and Tension-Compression Strength Difference of an Extruded ZK60 Mg Alloy

Multiroute yield experiments were carried out on extruded ZK60 magnesium alloy samples under 200 °C and strain rate of by a thermomechanical simulator [...]

Mechanical Behavior Characterization of Magnesium Alloy Sheets at Warm Temperature

Magnesium (Mg) alloy sheet has received increasing attention in automotive, transportation, and aerospace industries. It is widely recognized that magnesium sheet has a poor formability at room temperature. While at elevated temperature, its formability can be dramatically improved. To better understand the warm forming properties of magnesium alloy sheet, an accurate description of the mechanical behavior at elevated temperature is required.In this paper, both uniaxial tensile tests and uniaxial compression tests were carried out at warm temperature for Mg AZ31B alloy sheets. The tensile tests were conducted under various strain rates and material orientations, while the compression tests only considered different material orientations. Based on the orthotropic yield criterion for hexagonal close packed (HCP) metals proposed by Cazacu et al., 2006, a viscoplasticity model has been developed to describe the initial yield anisotropy and asymmetry hardening behavior in tensile and compression of Mg sheet. This model was incorporated into ABAQUS through a user-defined material subroutine. The numerical results show a good agreement with experimental data in a large range of deformation.

Directional Anisotropy in the Mechanical Behavior of Friction Stir Processed and Aged AZ91 Alloy

Friction stir processing (FSP) is an emerging grain refinement technique for magnesium alloys. In this study, a cast AZ91 alloy was processed by a single-pass FSP to achieve an average grain size of ~6 mm in the nugget zone. The FSP is found to introduce texture in the alloy due to preferred alignment of basal poles in the processing direction. The mechanical behavior is significantly influenced by texture. After FSP, the alloy was aged at different temperatures and times for continuous and discontinuous precipitation of b-Mg17Al12. A high anisotropy in yield stress is observed in the processing and transverse direction after FSP. It is shown that this anisotropy can be minimized under optimum ageing conditions. The observed yield asymmetry is correlated with the texture variation after FSP. The role of b-Mg17Al12 precipitates in reducing the yield anisotropy is also discussed.