Effects of Pre‐Strain on the Microstructural Evolution and Mechanical Strength of In Situ TiB₂/7050 Al Composite

The microstructure evolutions and mechanical properties of in‐situ TiB₂/7050 Al composites with a set of pre‐strains are investigated. This study shows that most quenched‐in residual stress can be removed by ≥1% pre‐strain. Meanwhile, the coupling of pre‐strain and TiB₂ particles within grains has a profound impact on mechanical properties of composites treated by the artificial aging. The yield strength increases with the increasing pre‐strain, i.e., the yield strength increases from 669 MPa to 697 MPa through 5% pre‐strain. Analytically, the pre‐strain is beneficial to the dislocation strengthening, but harmful to the precipitate strengthening during the aging process. Nevertheless, TiB₂ particles are beneficial to both dislocation strengthening and precipitate strengthening in the aging duration. As a result, the improvement in dislocation strengthening is found larger than the loss in precipitate strengthening, leading to the increment in yield strengths of artificial aged composites. The underlying mechanisms are discussed on the basis of quantitative theoretical analysis of diffusion‐controlled precipitation in combination with multi‐scale microstructure characterizations (i.e., scanning electron microscope, transmission electron microscope, small‐angle X‐ray scattering and X‐ray diffraction).