Changing distribution and geometry of S′ in Al-Cu-Mg single crystals during stress aging by controlling the loading orientation

The precipitation behavior of S′ phase in Al-Cu-Mg single crystals during stress-free and stress aging was investigated by transmission electron microscopy (TEM). Different compressive stress magnitudes and loading orientations were applied to determine their effects on the precipitation of S′ in Al-Cu-Mg alloy during stress aging. The results indicate that a noticeable preferential orientation of S′ is generated in the sample under applied compressive stress of 33 MPa loading along close to [001]Al, whilst no obviously preferential orientation of S′ can be observed in the sample loaded along close to [101]Al under the same applied stress or even larger applied stress. The precipitation distribution of S′ phase during stress aging can be changed by the loading orientation of the applied stress. Moreover, compressive stress aging may lead to S′ phase shorter in length, and the length of S′ phase shows a decreasing tendency with increasing applied stress, which are associated with the positive misfit between S′ and Al matrix.