Revealing the effect of oriented microstructures on the anisotropy of fatigue crack propagation behavior in TiB2/Al-Cu-Mg-Mn composite

The particle-reinforced metal matrix composite extruded plate exhibits oriented microstructures including elongated grains and aligned distribution of phases/particles, directly influencing the anisotropy in fatigue crack propagation (FCP). It is found that the crack advances perpendicularly to oriented microstructures when the load is parallel to the long axis of elongated grains (E-T sample), exhibiting the lowest FCP rate. When the sample is loaded along the short axis of elongated grains (T-E sample), the crack is parallel to the oriented microstructures, exhibiting the highest FCP rate. The influence of particles on crack propagation is dependent on the width of particle band. Narrow particle bands promote crack deflection and retard FCP. Wide particle bands weaken the hindering effect as numerous particles shorten dislocation slip distance. The rod-shaped T-Al20Cu2Mn3 dispersoids can carry larger load transfer than other two loading directions when the sample is loaded along extrusion direction. Overall, the geometric shielding from oriented microstructures is an important factor in the anisotropy of FCP. The particle-induced geometric shielding contribution is decreased in the case of loading perpendicular to particle bands, resulting in the enhancement of the FCP anisotropy behavior.