Fatigue Fracture Surface Analysis on Aluminium Reinforced Metal Matrix Composites on Chill Casting

Abstract

In this manuscript, an effort has been made through study the influence of copper chill in Aluminium Metal Matrix Composites (AMMCs), and also to explore the fatigue behaviour of the prepared aluminium A356-Hematite particulate metal matrix composite, which is cast through sand casting practice without and with copper chills at ends to get isotropic and homogeneous substantial properties under liquid metallurgical manner by varying weight fraction particulates of Hematite ranges from 0wt% - 12wt% in phases about 3wt%. The test samples stood prepared as per ASTM standards. Experiments were conducted to study the fatigue behaviour using ducom-type fatigue testing equipment. The result reveals that the composites cast with copper chills show superior fatigue strength as compared to the composites cast without copper chills. The micrographic analysis is performed using XRD (X-Ray Diffraction) patterns and SEM (Scanning Electron Microscope) photos. The existence of Hematite particles was confirmed from XRD and also found that the uniform dispersal of Hematite particles in the A356 matrix alloy of composites cast with copper chills. It was also observed that the fine-grained structure is obtained due to rapid cooling which influences improved fatigue strength in the composites with copper chills. The fractured surface of crack initiation and propagation along with fractography was studied with aim of SEM photos. The fractography images show the mode of fracture which is brittle in nature, signified by the cleavage facets from the transgranular crystallographic plane and striations. It is also observed that an improved content of reinforcement in both without and with copper chill mixtures results in a substantial development in fatigue strength. Copper chill fatigue specimen show higher fatigue strength than without copper chill specimen.