On the Effect of the Extrusion Speed on Microstructure and Plastic Deformation of ZE10 and ZEK100 Magnesium Alloys - an Acoustic Emission Study

Abstract

MgZn-based alloys ZE10 and ZEK100 have been extruded at dierent speeds varying from 1 m/min to 20 m/min. Specimens taken in the extrusion direction were uniaxially loaded in tension and compression at room temperature. The results are discussed using concurrent acoustic emission monitoring during mechanical testing and the acoustic emission signal analysis that correlates the microstructure and the stressstrain curves to the possible deformation mechanisms. In all tests, the acoustic emission response exhibited a large acoustic emission peak at the beginning of plastic deformation. A small local maximum on the onset of the acoustic emission activity was frequently observed, i.e. at very low stresses. For the alloys with bimodal grain structure tested in compression, an additional acoustic emission peak appeared at larger strains. This peculiar behavior can be explained by interplay of (1012)-twinning and dislocation slip in samples with various grain size distributions.