Grain-scale investigation of the anisotropy of Portevin-Le Chatelier effect in Mg AZ91 alloy

Journal
Materials Science & Engineering. A structural materials  
Volume
740-741
Start Page
226
End Page
234
Citation
Materials Science and Engineering A (740-741): 226-234 (2019-01-07)
Publisher DOI
10.1016/j.msea.2018.10.099
Scopus ID
2-s2.0-85055678044
An aspect of Portevin-Le Chatelier (PLC) type plastic instability that is yet to be understood is its orientation dependence. Such knowledge is crucial in view of its implications for texture weakening and, by extension, improvement in formability in Mg–based alloys. In this work, insight into the micromechanisms that govern PLC and its orientation dependence in single grains of Mg AZ91 is achieved using a combination of spherical nanoindentation, local orientation image analysis and crystal plasticity based finite element simulations, which was specifically used to identify the anisotropy in slip activity for the investigated orientations. Moreover, a statistical thermal activation model that is based on the distribution of load jumps between consecutive displacement bursts in the load vs. displacement response is presented. The paper demonstrates the ability of the model to predict the thermal activation parameters for PLC effect. On the basis of the results, we propose a mechanistically sound model for PLC effect that explains the underlying micromechanisms, the role of Al and Zn atoms, and the origin of the orientation dependence of the phenomenon. We also highlight the influence of the PLC effect on formability in Mg–based alloys.
DDC Class
600: Technology