Thermomechanical Deformation Response in Cold Sprayed SiCp/Al Composites: Strengthening, Microstructure Characterization and Thermomechanical Properties

Abstract

SiC_p/pure Al composites with different SiC_p fractions (20, 30 and 40 wt.%) were cold sprayed followed by hot axial-compression tests at deformation temperatures of 473 K (200 °C) to 673 K (400 °C), leading to failure of specimens through routine crack propagation in their multiphase. The plastic deformation behavior of the coating with respect to the SiC_p contents and the deformation temperatures were studied at strain rate 1 s⁻¹. As-sprayed and post-failure specimens were analyzed by x-ray computed tomography (XCT), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Quasi-static thermomechanical testing results revealed that compressive strength (UCS = 228 MPa) was the highest in the deposits that were compressed at 473 K compared to those of the as-sprayed, while the as-sprayed exhibited a compressive strength of 182.8 MPa related to the increment in SiC_p fractions. Strength-plasticity synergy was promoted by dynamic recrystallization (DRX) through strengthening and refinement of the grains. The DRX degree depends relevantly on grain refinement, higher deformation temperature and the pinning effects of the interfaces promoted by the ultrafine grain structures (UFG). Reconstructed XCT data revealed different crack propagation mechanisms. A single-plane shear crack with multi-laminates fracture morphology yields relatively through the as-sprayed and as-deformed at 473 K deposits, while a multiphase plane shear cracks preeminently existed in high temperature deformed deposits resulting in multiphase-interface delaminations. Three pertinent strengthening mechanisms, videlicet, SiC_p dispersed strengthening, refined grain strengthening and dislocation strengthening existed in the gradient microstructure, and their detailed contributions to the thermomechanical properties were discussed.