Hierarchical modification of bimodal grain structure in Al/Ti laminated composites for extraordinary strength-ductility synergy

Abstract

Al/Ti laminates with altering Al grain sizes was fabricated via hot press sintering. Fine Al powders results in low sintering density and obvious cracks at Al/Ti interface. Large Al powders greatly increased the grain size, grain aspect ratio, LAGBs fraction, and recrystallization fraction of the Al layers. The texture heterogeneity is also significant, with rolling texture in Ti layer and random texture in Al layer. Ti₅Si₃ phase precipitated at Al/Ti interface, and it gradually partitioned Ti atoms from TiAl₃ and hindered the formation of TiAl₃. Moreover, numerous stacking faults, dislocation loops, dislocation pinning, and dislocation tangles were observed at Al/Ti interface, resulting in an increased back stress. Large Al grains contributes the highest bending strength of 734.8 MPa, tensile strength of 753.2 MPa, and fracture strain of 71 %. The effect of grain size on work hardening was attributed to the fraction of LAGBs, dislocation storage capacity and additional HDI strengthening.