Study on the strengthening mechanisms and failure modes of the ultra-fine grained tri-modal Al5083-5wt. %B4C-Al2024 and Al5083-5 wt. %B4C-Al5083 composites

In this paper, the influence of Al2024 and Al5083 aluminum alloy coarse grains on mechanical properties and fracture mechanism of Al5083-B4C tri-modal composite has been discussed. Al5083 alloy powders with 5 wt. % of boron carbide were milled for 36 hours and 25 and 50 wt. % of coarse grain (CG) Al2024 and Al5083 powders were added to the milled powders and then hot press under argon atmosphere and hot extrusion were done. Comparing results revealed that adding Al2024 coarse-grains has led to a good ductility but at the same time, it has decreased the strength up to 30% compared to Al-5%B4C composite. In this case, adding 25 wt. % of Al2024 CG led to a decrease in strength from 508 to 379 MPa but elongation reached to 4%. Furthermore, in samples containing Al2024 CG strength drop was less compared to samples containing Al5083 CG. Comparing fracture surfaces of tri-modal composites revealed that by adding Al2024 CG, fracture mechanism changed and interface debonding occurred. The UFG/CG interface seemed to have a critical role in determining the failure mechanism.