Deformation mechanisms of basal slip, twinning and non-basal slips in Mg-Y alloy by micropillar compression

Micropillar compression technique was employed to study the microscale deformation mechanisms of basal slip, twinning and non-basal slips at selected grains in a Mg-2 wt.% Y alloy. The results suggest a critical resolved shear stress (tCRSS) for basal slip 12.5 +/- 1.7 MPa, and for twin nucleation and twin growth 38.5 +/- 1.2 MPa and 33.8 +/- 0.7 MPa, respectively. The higher values compared to those in pure Mg suggests a more balanced deformation in Mg alloy with Y addition. The activation of dislocations in the twinned orientation is highlighted, which leads to strong work hardening in twinned favorable orientation [1010]. In addition, at prismatic-slip favorable orientation [1120], a twinning-to-prismatic slip transition was observed when elevating temperature from 25 degrees C to 100 degrees C and 250 degrees C. Specially at 250 degrees C, twinning was completely prohibited, and pure prismatic slip was triggered. The measured tCRSS for prismatic slip at 250 degrees C was 39.7 +/- 0.3 MPa, much higher than that for pure Mg at the same temperature. Finally, at pyramidal-slip favorable orientation [0001], an abnormal strengthening was observed at 100 degrees C and 250 degrees C due to activation of pyramidal slips. Decompositions of dislocations and Y segregation at stacking faults are the main mechanisms leading to the hightemperature strengthening in Mg-Y alloy.

Automated summary

The addition of Y element in Mg-2 wt.% Y alloy results in a more balanced deformation compared to pure Mg, with different mechanisms of deformation observed in basal slip, twin growth, and prismatic-slip favorable orientation. The high-temperature strengthening in Mg-Y alloy is mainly attributed to dislocation decomposition and Y segregation at stacking faults.