In situ characterization of tensile behavior of laser rapid solidified Al–Si heterogeneous microstructures

Heterogeneous Al–Si microstructure comprising of sub-micron-scale Al dendrites and nanoscale Al–Si fibrous eutectic was fabricated by processing as-cast Al-20wt.%Si alloy using laser rapid solidification. In situ tension tests explored high tensile strength (∼600 MPa) and ductility (∼10%) and high strain hardening rate (∼7 GPa). Microstructural characterization revealed the plastic co-deformation mechanisms between soft Al dendrites and hard nanoscale Al–Si eutectic. The progression of plasticity in nanoscale Al–Si eutectic with increasing applied strain is accommodated by dislocation plasticity in the nano-Al channels and cracking Si nanofibers. The propagation of nano-cracks is suppressed by surrounding Al, retaining good ductility of the sample. In situ tension tests revealed the role of heterogeneous Al–Si microstructure in enhancing strain hardening rate and producing large back stresses and plasticity in sample even after fracture of nanoscale Si fibers.