In-situ investigation on β-Fe induced tensile fracture mechanism of A356 aluminium alloy

Abstract

Direct evidence for the fracture failure of aluminum alloys induced by the β-Al5FeSi phase is lacking. To ascertain the microstructural origin of the β-Al5FeSi phase-induced failure in A356 alloys, the local strain distribution of the Al5FeSi phase during deformation was quantified by combining Digital Image Correlation (DIC) strain analysis with in-situ SEM observations during tensile tests. The results indicated significant strain localization in the regions containing the β-Al5FeSi phase. TEM findings revealed that its monoclinic crystal structure is prone to high-density twinning and dislocations, which makes it difficult to undergo uniform, accommodated deformation. Moreover, the weak interfacial bonding between the β-Al5FeSi phase and the α-Al matrix, along with nanoparticles near the interface, exacerbates stress concentration.