Fig. 8 TEM (a, b) and HRTEM images (c) of matrix precipitates in BM sample. The inverse FFT images after mask to the phases in (c) image are shown in (d).
As shown in Fig. 9a, sub-grains could also be observed in AS-HAZ. Some discontinuous chain-typed 𝜂 (MgZn2) equilibrium phases formed in grain boundary and the PFZ were obviously observed. As compared with BM, the size of 𝜂′ precipitates in grains increased slightly (Fig. 9b). It should be noted that the projections of some precipitates showed short rod-shaped morphology while the others displayed the round morphology, depending on the direction of observation [27]. According to HRTEM observation, all of the 𝜂′ precipitates remain semi-coherent relationship with matrix (Fig. 9c and 9d). No clear GPII zones were identified in AS-HAZ.