Tensile creep anisotropy of a Mg-2Y alloy extruded sheet with a splitted texture

Mg-RE based alloys usually exhibit better creep resistance than traditional RE-free Mg alloys. Creep anisotropy can be still found in Mg-RE alloys but barely investigated. Thus, in the present study, tensile creep anisotropy and creep mechanisms were studied in a dilute Mg-2Y alloy extruded sheet. It is found that tensile creep property shows not only obvious stress and temperature dependences but also strong anisotropy. Varied stress exponent n is obtained under different conditions. Under o < 40 MPa at T = 493 K, n = 2 is shown and grain boundary sliding is the main creep mechanism. Under o < 40 MPa at T = 523 and 553 K, n = 3-4 is obtained and dislocation motion gradually dominates the creep. Under o > 40 MPa at all temperatures, n > 4 is seen and intense dislocation slip becomes the predominant deformation mode. Besides, steady-state strain rate es and n are always higher along ED than TD. This creep anisotropy is caused by different dislocation slip types. Basal slip plays the most important role in the creep anisotropy under o < 40 MPa and non-basal slip contributes to the anisotropy under o > 40 MPa. Heavy basal slip and pyramidal slip are the main mechanism during the creep along ED while cross-slip of dislocations plays the dominant role along TD. Furthermore, {1012} anomalous twins are more likely to be found in samples crept along ED with a smaller Schmid factor for twinning. Anomalous twinning and pyramidal slip contribute to the creep fracture of ED sample. Unlikely, cross-slip composed by basal and prismatic dislocations induces the fracture of TD sample. (C) 2020 Elsevier B.V. All rights reserved.