Anomalous {101¯2} tensile twinning and subsequent detwinning in a friction stir processed carbon fiber-reinforced Mg composite

• Anomalous tensile twinning and subsequent complete detwinning were observed, for the first time, using in-situ EBSD during tensile loading in a friction stir processed model carbon fiber-reinforced Mg composite. • This twinning-detwinning phenomenon is shown to result from the dynamic changing of local stress/strain state during tensile, which in turn accommodates strain incompatibility between the reinforced phase and matrix at different stages.