Formation mechanisms of high-density growth twins in aluminum with high stacking-fault energy

Nanotwins readily form in numerous face-centered-cubic (fcc) metals with low stacking-fault energy (SFE). However, growth twins rarely form in Al due to its high SFE, ∼120–165mJ/m². Here, using thin inter-layers or buffer layers of a low-SFE fcc metal (Ag), we overcome the SFE barrier and successfully grow high-density coherent and incoherent twin boundaries into Al. We identify three mechanisms that induce growth twins in Al and demonstrate enhanced mechanical strength in twinned Al. This study reveals an effective means that may be generalized to control growth twin formation in fcc metals with high SFE.