Microtwinning in Ni-base supalloy Mar-M247 at intermediate temperature and low stress

•The substructures in Mar-M247 are studied after creep rupture at 760 °C/470 MPa.•APB shearing occurs in Mar-M247 during creep deformation.•Stacking fault shearing occurs in Mar-M247 during creep deformation.•Microtwinning occurs in Mar-M247 during creep deformation. After creep deformation at 760 °C and 470 MPa, approximately half of the yield strength, for 7075 h, the deformation microstructures of Mar-M247 are investigated using transmission electron microscope. Experimental results reveal that pairs of a/2 〈110〉 dislocations, superlattice stacking faults and microtwins are produced in the deformed specimens, suggesting anti-phase boundary shearing, stacking fault shearing and microtwinning operate simultaneously during creep deformation. This study provides new insights into understanding the creep deformation mechanisms in Ni-base superalloy.