Fatigue life, distortion behavior of AA 8011- nano B4C composite using simulated acoustic emission technique – An experimental and statistical appraisal

Abstract

The high quality AA8011 aluminium alloy dispersed with different percentages of nano-sized B4C (0, 0.5,1 and 1.5 wt%) was fabricated by electromagnetic frequency high energy stir casting technique. The characterization study on metal matrix nanocomposites (MMNC) using Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive Spectrum (EDS), and X-ray Diffraction (XRD) confirmed the morphology and distribution of AA8011 with nano B4C. The microhardness analysis and strength using Vickers hardness testing and Electromechanical Universal Testing Machine, respectively, show significant mechanical properties improvement. The ductility study on Scanning Electron Microscope (SEM) images of the fractured samples reveal the transition from ductile to brittle nature in MMNCs. The online monitoring using Acoustic Emission (AE) during a tensile test indicates the mitigation in crack generation and its propagation. The substantial enhancement in fatigue life by the addition of nano B4C was evidenced by testing at a stress ratio (R = 0.1) and statistically significant (at p < 0.05) by one way Analysis of Variance (ANOVA). The SEM Fractography of fractured fatigue samples discloses the influence of dispersal of nano-sized reinforcements which resist fatigue crack growth. The result demonstrates that AA8011-1.5 % nano B4C composite has improved hardness, higher tensile strength and fatigue strength than the pure matrix due to the addition of the B4C.