Fig. 9 TEM images (a, b) and HRTEM image (c, d) of matrix precipitates
in the AS-HAZ sample.
In WNZ, sub-grains turned to be recrystallized structure due to high
weld heat input, and some Al3(Sc,Zr) particles grew
slightly (Fig. 10a). It is noted that the Ashby-Brown contrasts of the
grown Al3(Sc,Zr) particles become irregular, indicating
that the coherency would be break down during welding.
It can be observed that new 𝜂
equilibrium phase tended to attach to the grown incoherent
Al3(Sc,Zr) particles and overgrew. In addition, a
considerably amount of nanoscale
rod-shaped 𝜂′ phase and GPII zones also be observed at higher
magnification (Fig. 10b).