Strength and fracture of aluminum alloys

In aluminum alloys, it is general that dimple type fracture occurs from inclusions or second phases particles. Intergranular, local shear and delamination type fractures are also sometimes observed. On Al–Li alloy (A2091), effect of inclusion particles on fracture behavior is analyzed using HRR singularity and Eshelby type internal stress analysis. Fracture of inclusions of CuAl2 and Al2CuMg is observed (5–8 μm) and their strength is estimated about 710 MPa and decreased with increasing particle size. Fracture of Al3Zr or Al3Ti particles is not observed. Moreover, it is clarified that delamination occurs when the normal stress against the grain boundary attains 116 and 113 MPa at liquid He and room temperature, respectively. Moreover, newly developed high strength Al–Nb wire with 1 Gpa is introduced. Fracture and fatigue behaviors of aluminum casting alloys are also stated. Increasing the iron content, fracture toughness and fatigue properties (also impact fatigue properties) are degraded. The effect of Ca addition that possesses the modifying effect of the eutectic Si morphology is examined. It has been observed that the harmful effect of iron is largely improved. Increasing the Si content in Al–Si casting alloys, it is generally observed that fatigue strength or ΔKth is increased. Toughness of MMC is generally rather low. Based on the simulation analysis on fracture of Al–SiCW composite, high toughness MMC has been already developed, where some aggregated SiCW granules have been embedded into A6061 matrix. According to FEM analysis, it has been suggested that there is an appropriate aggregation ratio in the granule (i.e. SiCW content in the granule). The above topics have been reviewed.