Effect of pre-cold rolling on the evolution of microstructure, microtexture, and mechanical properties of the mushy state rolled in-situ Al-4.5Cu-5TiB2 composite

Abstract

The mushy state rolling has been found as a promising technique for near-net forming of the cast Al-4.5 wt% Cu-5 wt% TiB2 in-situ composite to obtain microstructural refinement and moderate mechanical properties. Cold rolling with 30% reduction in thickness was carried out before mushy state rolling, for achieving a relatively more homogeneous distribution of CuAl2-TiB2 particles as well as an appropriate microstructure to enhance the mechanical properties. A comparative investigation on the microstructural and microtextural evolution, along with mechanical properties of both the mushy state rolled composite (MRC) and pre-cold rolled mushy-state rolled composite (PCMRC) was performed, and the microstructure-property correlation was established. The PCMRC exhibited the lowest homogenized lengthscale parameter (LH 29 μm) indicating the maximum uniformity of particle distribution, computed with the help of multi-scalar analysis of area fractions (MSAAF) technique. Electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) studies revealed the presence of fine sub-grains within centrally located deformed Al grains due to dynamic recovery, as well as the particle stimulated nucleation of equiaxed fine Al grains by dynamic recrystallization or rapid solidification of liquid near edges for both the investigated composites. The PCMRC displayed a superior combination of hardness (96.82 ± 4.5 HV5kgf), 40% higher ultimate tensile strength (301.4 ± 1.8 MPa), and 68% more uniform elongation (30.8% ± 0.5%), compared to the MRC. The improvement in mechanical properties is attributed to the uniform particle distribution and presence of both higher density of low angle boundaries and recrystallized grains adjacent to the particles, obtained from prior cold rolling.