Grain refinement and mechanical properties enhancement on inclusion of Al2O3 in AA 7017 alloy synthesized by mechanical alloying (MA) and hot pressing (HP)

Abstract

Present research work aimed to study the volume percentage of Al2O3 (5 %, 10 % and 20 %) and milling time (0, 5, 10, 15 and 20 h) on the morphology, phase formation and mechanical behavior of nanocomposite. The milled nanocomposite powder and hot-consolidated samples (500 MPa and 400 °C) were characterized using PSA, XRD, SEM and TEM. The grain structure, grain size and elemental composition were examined using HRSEM and EDS. The TEM results confirmed the formation of nanocomposite nature of milled powder samples in which 20 h milled powders produced the crystallite size of 15.56 ± 1.05 nm, 15.28 ± 1.11 nm and 15.61 ± 1.20 nm for 5 %, 10 %, and 20 % Al2O3 reinforced samples, respectively. The hot-consolidated TEM samples were collected at 10 vol% of Al2O3 reinforcement due to the higher mechanical properties. The developed nanocomposite samples exhibited higher hardness (152–250 VHN) and compressive stress (501–893 MPa) when reinforced with 10 vol% of Al2O3 compared to that of 5 vol% Al2O3 and 20 vol% Al2O3. The improvement in the hardness and compressive strength of the specimens was due to the variation in the morphology of the specimen and the homogeneous distribution of the Al2O3 reinforcement. The contribution of the strengthening mechanism to the total strength of the specimen was studied for 10 vol% of Al2O3 reinforcement for different milling times.