An investigation of the deformation and cracking mechanism of Mg–1Al–12Y alloys based on in-situ SEM/EBSD slip trace analysis

Abstract

In this work, the deformation mechanism and cracking behavior of Mg–1Al–12Y alloys with different contents of long-period stacking ordered (LPSO) phase during in-situ tensile testing at ambient temperature were investigated in detail using a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The slip trace analysis results showed that the deformation of the three alloys was all dominated by dislocation slip and supplemented by extension twinning. The predominant slip deformation mode was basal <a> slip. The Mg–1Al–12Y alloy after solution treatment at 540 °C for 4 h (T4-4h) exhibited higher elongation due to greater non-basal slip activation (31.8%) and cross slip occurrence (10.4%) and lower twinning activity. This was primarily attributed to the fact that profuse lamellar LPSO phases in the matrix of T4-4h alloy promoted the activation of non-basal slip and inhibited the initiation of extension twins. In addition, crack nucleation of the three alloys was mainly concentrated at the grain boundaries and triple junction of the grain boundaries. Nucleation and crack propagation were mostly attributed to the surrounding grains with a hard orientation and the second phase at the grain boundaries, which was not conducive to coordinated deformation.