Abstract
This study is aimed at understanding the tensile ductility and compressive strength-enhancing dual function of nanoparticles in a concentrated magnesium alloy (AZ81) nanocomposite. Si3N4 nanoparticles were selected for reinforcement purposes due to the known affinity between magnesium and nitrogen. AZ81 magnesium alloy was reinforced with Si3N4 nanoparticles using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size and hardness to the monolithic alloy, reasonable nanoparticle distribution, and nondominant (0 0 0 2) texture in the longitudinal direction. Compared to the monolithic alloy in tension, the nanocomposite exhibited higher failure strain (+23%) without significant compromise in strength, and higher energy absorbed until fracture (EA) (+27%). Compared to the monolithic alloy in compression, the nanocomposite exhibited similar failure strain (+3%) with significant increase in strength (up to +20%) and higher EA (+24%). The beneficial effects of Si3N4 nanoparticle addition on tensile ductility and compressive strength dual enhancement of AZ81 alloy are discussed in this paper.
Highlights
Silicon nitride nanoparticles in the shape of near-spheres and wires have been synthesized by chemical vapor deposition (CVD) [1, 2]
AZ81 was reinforced with Si3N4 nanoparticles using solidification processing (disintegrated melt deposition (DMD) [14, 15]) followed by hot extrusion
The tensile/compressive yield stress anisotropy was desirably lower in AZ81/Si3N4 compared to monolithic AZ81. This can be attributed to the AZ81-Si3N4 nanoscale interface being relatively weaker in tension but relatively stronger in compression
Summary
Silicon nitride nanoparticles in the shape of near-spheres and wires have been synthesized by chemical vapor deposition (CVD) [1, 2]. (b) ease of handling, (c) good strength and ductility, and (d) resistance to atmospheric corrosion [5] These qualities enable the common use of AZ series magnesium alloys [5]. High strain rate superplasticity was exhibited taking into consideration the sufficiently uniform dispersion of SiO2 nanoparticles In another case, the superplasticity of Mg-Zn-Zr composite systems containing SiC microparticles or submicroparticles has been studied and attributed to (a) fine grain size (lesser twinning effects) and (b) crystallographic textural effects [7, 8]. Regarding concentrated AZ series magnesium alloys (e.g., AZ80 and AZ91), the Mg-Al second phase presence significantly contributes to strengthening. Not much is known about the interplay between nanoscale reinforcement presence and second phase precipitation (which is especially relevant in concentrated magnesium alloy nanocomposites) concerning the effects on mechanical properties. AZ81 was reinforced with Si3N4 nanoparticles using solidification processing (disintegrated melt deposition (DMD) [14, 15]) followed by hot extrusion
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