Stress Corrosion Cracking and Hydrogen Embrittlement of Whisker-Reinforced Aluminum Composites Available to Purchase

Stress corrosion cracking (SCC) in an 3.5% sodium chloride (NaCl) aqueous solution, hydrogen-induced cracking (HIC) during dynamic charging, and hydrogen embrittlement (HE) after precharging of whisker-reinforced aluminum composites were studied. For all four aluminum composites with the whisker direction perpendicular to the normal stress, SCC occurred but no SCC occurred if the whisker direction of Al₁₈B₄O₃₃/Al was parallel to the normal stress. The threshold stress intensity of SCC (K_ISCC), measured using double cantilever beam (DCB) specimens, was (0.94 to 0.70)K_IC, where K_IC is the fracture toughness. The susceptibility to SCC, measured by slow strain rate test (SSRT), was 24% for SiC/Al and 13% for Al₁₈B₄O₃₃/Al. The susceptibility to HE of Al₁₈B₄O₃₃/Al was 44%. HIC occurred during dynamic charging under Mode II loading and the threshold stress intensity was K_IIH = 0.85K_IIC for SiC/Al and 0.88 K_IIC for Al₁₈B₄O₃₃/Al, respectively. The results show that the existence of the whisker/Al interface is a necessary condition of SCC of the whisker-reinforced pure aluminum composites, and the reason must be investigated further.