Effect of reinforcement particle size on quasistatic and dynamic mechanical properties of Al-Al2O3 composites

Herein, high-energy ball milling and hot pressing are employed to synthesize Al-15 vol.% mm Al2O3 (AlMMC) and Al-15 vol.% nm Al2O3 (Al-MMNC) composites and the influence of reinforcement particle size (3 mm and 50 nm) on mechanical properties has been systematically studied. The as-prepared Al-MMNC samples rendered superior mechanical properties than Al-MMC and pure Al, with an improved yield strength and ultimate strength of 610 MPa and 784 MPa under quasistatic compression, respectively. Moreover, the flow stress of Al-MMC and Al-MMNC increased with increasing strain rate, and Al-MMNC exhibited higher flow stress than Al-MMC due to the smaller particle size. It is worth noting that the ultimate strength of Al-MMNC reached 963MPa under the loading rate of 2200 s(-1). Moreover, unlike previously reported Al-based nanocomposites, Al-MMNC exhibited strain hardening and strong strain rate sensitivity, which is highly desirable for engineering applications. Lastly, the ex-situ SEM analysis revealed the presence of microcracks and dimples on the fractured surface of Al-MMNC, which led to the ductile fracture mode under quasistatic compression. Moreover, the adiabatic shear under high strain rate loading has also been observed in Al-MMNC, but the high volume fraction nanoparticles inhibit adiabatic shear band development, and result in strain hardening and strong strain rate sensitivity. (C) 2019 Elsevier B.V. All rights reserved.