Effects of Effective Dendrite Size on Tensile Deformation Behavior in Ti-Based Dendrite-Containing Amorphous Matrix Composites Modified from Ti-6Al-4V Alloy

Five composite sheets having different thicknesses were fabricated by varying cooling rates after a vacuum arc melting of a Ti-based amorphous matrix composite fabricated by adding alloying elements of Ti, Zr, V, Ni, Al, and Be into a Ti-6Al-4V alloy. These composite sheets contained 72 to 75 vol. pct of dendrites sized by 9 to 27 μm, and showed excellent tensile properties of yield strength of 1.3 GPa and elongation up to 6.5 pct. According to the observation of tensile deformation behavior of the 3-mm-thick composite sheet, many deformation bands were formed inside dendrites in several directions, and deformation bands met crossly each other to form widely deformed areas. Since the wide and homogeneous deformation in this sheet beneficially worked for the tensile strength and elongation simultaneously, the optimum effective dendrite size (12.1 μm) and sheet thickness (3 mm) were determined for the Ti-based amorphous matrix composite. The finite element method (FEM) analysis based on real microstructures was also conducted to theoretically explain the enhanced elongation in terms of effective dendrite size. The shape and location of deformation bands estimated from the FEM simulations were well matched with the experimental observations.