Effects of TiB2 particle and local aspect ratio on microstructure and mechanical properties of an I-shaped TiB2/6061Al composite profile

Abstract

The I-shaped profiles of TiB2/6061Al composite were fabricated by hot pressing sintering and hot extrusion. The effects of TiB2 particle and local aspect ratio on microstructure and mechanical properties were clarified. The results show that TiB2 particles homogeneously distribute in the I-shaped profile. The web and flange of I-shaped profile own different amounts of TiB2 particles, and the web contains more particles than the flange. The interface between TiB2 and Al matrix is in a strong bonding status without defects, and there is a Mg-rich layer accompanied by lots of misfit dislocations around TiB2 particle. The elongated grains in web are significantly narrower than those in flange because of its larger aspect ratio. TiB2 particle promotes the dynamic recrystallization (DRX) during hot extrusion through particle stimulated nucleation mechanism. The DRX fraction of the web is higher than that of the flange due to the higher particle content and larger aspect ratio. The web owns strong brass as well as some weak Dillamore and R textures, while the main textures of flange are A, copper and Dillamore. The addition of TiB2 particles reduces the intensity of main textures but cannot change the types of orientation preference. Adding TiB2 particles and increasing its content enhance the tensile strength and wear resistance through the load transfer, dislocation strengthening and Orowan strengthening mechanisms. The higher DRX fraction and Schmid factor result in higher elongation and lower strength of the web compared to the flange on an I-shaped profile.