Aluminum matrix composites (AMCs) combine low density, high specific strength, wear resistance, and thermal management capability, but reinforcement-induced interfaces, residual stresses, and microstructural heterogeneity may promote localized corrosion and environmentally assisted cracking (EAC). This review focuses on EAC of AMCs in aqueous environments, particularly stress corrosion cracking and hydrogen-assisted cracking, while corrosion fatigue is considered selectively. Anodic dissolution, hydrogen-assisted damage, passive film rupture, interfacial debonding, and crack-tip chemistry are examined in relation to the condition-dependent transition from localized corrosion to crack initiation and propagation. EAC testing and complementary characterization methods are compared, with attention to AMC-specific interpretation. The effects of matrix composition, reinforcement characteristics, grain-boundary precipitation, interface structure, processing, residual stresses, environment, loading, and heat treatment are critically assessed. Conflicting trends are interpreted through stage-dependent electrochemical, mechanical, interfacial, and hydrogen-related effects. Direct AMC-EAC evidence is distinguished from corrosion-precursor, mechanical-only, and transferred evidence, with conclusions qualified by data comparability. Mechanism-guided mitigation strategies involving alloy design, interface engineering, processing optimization, surface protection, and surface mechanical treatments are discussed, followed by unresolved questions and experimental priorities for improving AMC durability.
The oxidation behavior of a Ni–5Cr (at.%) alloy was evaluated at 420 ° C using the Rhines pack method and simultaneous tensile and compressive stress states via a miniature four-point bending fixture. At this moderate temperature, grain boundaries dominate mass transport and the resulting oxidation response. Oxidation produced approximately 1μm-wide protective Cr2O3 films capping some grain boundaries and penetrative, intergranular Cr-rich oxides at other grain boundaries. Externally applied tensile and compressive stress during oxidation increased the prevalence of Cr2O3 cap formation compared to no applied stress, with tensile stress resulting in more Cr2O3 caps than compressive stress. The observed oxide cap morphology was similar across all test conditions. Regions under compressive stress showed an order of magnitude greater Cr depletion depth along the grain boundary. Chromium nitrides (CrN), likely from N contamination of the Rhines pack cell, were observed both at the oxide–metal interface and intergranularly within the alloy. Collectively these results demonstrate that applied stress promotes localized protective oxide cap formation over grain boundaries, with compressive stress additionally promoting deeper Cr depletion. The experimental approach helped separate out the effects of stress on local oxide formation and grain boundary passivation.
