Influence of strain rate on deformation behaviour of an AX52 alloy processed by equal channel angular pressing (ECAP)

Abstract

Cast AX52 magnesium alloy with Al and Ca was processed by equal channel angular pressing (ECAP) using A route and 1 -8 passes. The light and electron microscopy revealed a substantial microstructure refinement in the alloy. Al 2 Ca eutectics were found to be typical features of the microstructure. The ECAP procedure disintegrated eutectic particles. Miniaturized samples were cut from the ECAP-processed bulks. The samples with the tensile axis parallel to the extrusion direction were tested in tension at room temperature with initial strain rates of 0.001, 1, 10 and 50 s −1 . The offset yield stress increased with increasing number of passes. A rapid increase of deformation stresses was observed for the highest strain rate of 50 s −1 . The activation volumes were estimated from the strain rate dependence of the offset yield stress. The strain rate sensitivity is influenced by the number of passes. A rapid increase of the activation volume at the highest strain rate indicates the change of the deformation mechanism. Limiting small values of the activation volume were found for the highest strain rates. Tensile tests at higher strain rates revealed unstable deformation behavior. This unstable deformation depends on the number of passes. Mechanisms operating at various strain rates are discussed in relation to the microstructure and number of ECAP passes.

Local Mechanical Properties and Microstructure of EN AW 6082 Aluminium Alloy Processed via ECAP–Conform Technique

“…Samples for miniaturized tests were carefully machined from wires to reach their final shape and dimensions (active length of 3.0 mm, width of 1.5 mm and thickness of 0.5 mm)-see Figure 3. The sample geometry is very similar to the one that was used for the experimental investigation of a magnesium alloy by Máthis [21], where the shorter active length was used. As the final step of specimen preparation, the surface roughness was polished.…”

“…Unfortunately, this approach is unable to describe elastic or plastic behavior during the loading, which provides the experimental data necessary for computer modeling. A small amount of the experimental material and local mechanical properties can be therefore investigated by miniature flat tensile specimens [19][20][21]. This method may be applied for micro-or ultrafine-grained samples where a large number of grains per sample cross-section ensures good reproducibility of experimental results.…”

Strengthening and Thermally Activated Processes in an AX61/Saffil Metal Matrix Composite

“…The detailed analysis showed that Mg-Al-Ca alloys contain various second phases of Laves type depending on Ca/Al ratios and thermal treatment [16]. Further improvement of mechanical properties is possible using some method of severe plastic deformation [17][18][19][20]. These methods, such as equal channel angular pressing (ECAP), high pressure torsion (HPT) or repetitive corrugation and straitening (RCS), are not yet able to prepare bigger work-pieces of a material.…”