Engineering of strong and hard in-situ Al-Al3Ti nanocomposite via high-energy ball milling and spark plasma sintering

Abstract Light-weight Al-Ti nanocomposites attract increasing attention due to the advancements in spacecraft and additive manufacturing. In this work, ab initio modeling, DSC, and in-situ XRD experiments were used to formulate a strategy for rapid fabrication of Al-Al3Ti nanocomposites with enhanced mechanical properties (ultimate tensile strength up to 437 MPa at room temperature and up to 109 MPa at 500 ℃, ~6% elongation before failure), resulting from a mixed ductile-fragile deformation behavior. The investigated samples were produced by spark plasma sintering of high-energy ball-milled reactive composites Al-TiH2 leading to the precipitation of 0.05-0.25 µm Al3Ti particles from the nanostructured Al matrix. Samples with coarser TiH2 powder or higher TiH2 content featured a minor amount of transitional core-shell structures resulting from the incomplete conversion of the as-formed Ti particles into Al3Ti. The following phase and structure formation mechanism upon the heating of the reactive nanocomposite powders was proposed: Al + δ ­TiH 2 → ~ 450 − 500 ℃ Al [ Ti ] + β ­Ti [ Al ] + δ ­TiH 2 − x → ~ 550 − 600 ℃ Al + Al 3 Ti . Tentative guidelines for the sintering of Al-TiH2 composites were proposed based on the analysis of diffusion kinetics.