Study of basal < a > and pyramidal < c + a > slips in Mg-Y alloys using micro-pillar compression. Issue 11 (2nd June 2020)

• Record Type: Journal Article
• Authors: Wu, Jing; Si, Shanshan; Takagi, Kosuke; Li, Tian; Mine, Yoji; Takashima, Kazuki; Chiu, Yu Lung
• Is Part Of: Philosophical magazine. Volume 100:Issue 11(2020)
• Page Start: 1454
• Page End: 1475
• Publication Date: 2020-06-02
• Subjects: Mg-Y -- micro-pillar compression -- CRSS -- pyramidal slip -- twinning; Condensed matter -- Periodicals; Physics -- Periodicals; Matière condensée -- Périodiques; Physique -- Périodiques; 530.41
• DOI: 10.1080/14786435.2020.1725250
• Languages: English
• ISSNs: 1478-6435

Abstract

ABSTRACT: The effect of yttrium (Y) on the critical resolved shear stresses (CRSS) of < a > basal slip, { 10 1 ¯ 2 } ⟨ 1 ¯ 011 ⟩ tension twinning and < c + a > pyramidal slip has been studied using micro-pillar compression tests along selected orientations at room temperature, on two magnesium (Mg) alloys with different Y contents (0.4 and 4 wt.%). The CRSS of < a > basal slip increased slightly from 30 ± 1 MPa (for Mg-0.4Y) to 37 ± 3 MPa (for Mg-4Y). In Mg-0.4Y, the resolved shear stress to activate the { 10 1 ¯ 2 } ⟨ 1 ¯ 011 ⟩ tension twin was determined to be 45 ± 12 MPa, while in Mg-4Y it was 113 MPa. The compressed samples were studied using scanning electron microscopy (SEM), transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM). It was found that < c + a > dislocations slip mainly on { 1 ¯ 1 ¯ 22 } (Pyra II) planes with a CRSS of about 119 MPa in Mg-0.4Y and slip mainly on { 0 1 ¯ 11 } (Pyra I) planes in Mg-4Y with a CRSS of 106 MPa. There is a significantly lowered CRSS ratio between < c + a > slip and < a > basal slip in both alloys (2.8 and 4.8) compared with that reported in bulk pure Mg (∼100). The easy activation of < c + a > on Pyramidal I slip is expected to promote the frequent cross-slip in Mg-4Y alloy.