Fracture strength characterization of protective intermetallic coatings on AZ91E Mg alloys using FIB-machined microcantilever bending technique

摘要

The fracture strength of β-Mg_(17)Al_(12) and τ-Mg_(32)(Al, Zn)_(49) intermetallic coatings on AZ91E Mg alloy was investigated using a nanoindentation-based microcantilever bending technique. A set of micrometer-sized cantilevers with varying dimensions were machined using focused ion beam milling. A nanoindenter was then used to apply an increasing bending load until each cantilever fractured. The corresponding linear-elastic finite element models were created to simulate the deflection of the cantilevers and the fracture strength σ_m was derived from the models. The results showed that the fracture occurred at the root of the cantilever where the tensile stresses were highest; the average fracture strengths of the β-Mg_(17)Al_(12) and τ-Mg_(32)(Al, Zn)_(49) phases were 1.76 and 1.05 GPa, respectively. The potential sources of error are also discussed.