Experimental investigation on mechanical and metallurgical characteristics of magnesium metal matrix composites reinforced with hafnium carbide

Abstract

In recent times, a lot of research is being conducted for developing newlinestrong materials. Developments in manufacturing, automobile, power and newlineaerospace sectors require corrosion, wear and fatigue resistant materials newlinewhich can withstand rough and volatile environments. Metal Matrix newlineComposites (MMCs) are being used in many sectors as they exhibit enhanced newlinemechanical and metallurgical characteristics, compared to their parent alloy newlinematerial. Even though a lot of research is being conducted in developing newlinedifferent combinations of MMCs, there is a tremendous scope for newlineimprovement. Magnesium and its alloys are preferred over other materials as newlinethey have low density, high strength, ease of machinability, good thermal newlineconductivity and appreciably good corrosion resistance. At high temperature newlineoperations, creep and wear resistance of Magnesium (Mg) based alloys drops. newlineMMCs prepared using Mg based alloys can withstand external wear and newlinetough environment. The properties of Mg MMCs can be enhanced by using newlinedifferent types of reinforcements such as Carbides, Ceramics, Cermets etc. newlineThe composite preparation process, geometry of the reinforcements and the newlinequantity of reinforcements in MMCs should be chosen properly as they affect newlinethe strength of MMCs. newlineIn this research, Mg based MMCs were prepared using stir casting newlineprocess. Three Mg based alloys such as AZ31 Mg, ZE41 Mg and AZ91 Mg newlinewere selected to be the matrix material. AZ31 Mg material is a wrought alloy newlineexhibiting excellent strength, ductility, formability and machinability at room newlinetemperature. ZE41 Mg is a casting alloy comprising of zirconium and rare newlineearth materials. ZE 41 Mg alloy exhibits excellent weldability and castability. newlineAZ91 Mg alloy is a light weight material containing Al. AZ91 Mg alloy newlineiv newlineexhibits excellent corrosion resistance and high strength. Hafnium Carbide newline(HfC), a hard refractory material, was used as reinforcements. HfC exhibits newlinecubic crystal structure and has very high melting and boiling point. Using stir newlinecasting process, HfC reinforced Mg MMCs were prepared at three newlinereinforcement percentages such as 5% HfC, 10% HfC and 15% HfC. newlineCharacterization of the prepared Mg MMCs such as AZ31-HfC MMCs, newlineZE41-HfC MMCs and AZ91-HfC MMCs were done. Upon reinforcing Mg newlinealloys with HfC variations in yield strength (YS), ultimate tensile strength newline(UTS) and percentage of elongation was observed, by conducting tensile tests. newlineOn increasing the reinforcement by wt. percentage of HfC till 10%, increase newlinein YS and UTS was observed. Increase in HfC reinforcements beyond 10% newlinecaused reduction in YS and UTS. Percentage of elongation was found to newlinereduce steadily upon increasing HfC reinforcements. From 0% HfC to 15% newlineHfC reinforcement, consistent increase in micro hardness was observed. newlineUsing Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and newlineElectron Back Scattering Diffraction Studies (EBSD) microscopic newlineinvestigations on HfC reinforced Mg MMCs were done. newlineOptical microscopic images indicated annealed structures in Mg newlineMMCs. On adding HfC reinforcements, evenly mixed structure was observed newlinetill 10% by weight. On increasing reinforcement percentage of HfC beyond newline10%, chaotic mix with agglomerations was observed. SEM investigations newlinerevealed annealed and fine grained Mg material with HfC reinforcements. newlineDistinct boundary between Mg matrix and HfC reinforcements was observed. newlineEBSD evaluation revealed dynamic grain recovery mechanism and grain newlinestrengthening. Twinning was observed at certain regions. Grain growth was newlineobserved upon increasing the reinforcement percentage of HfC. A newlineconsiderable increase in the average particle sizes was observed upon newlineincreasing the reinforcement percentage. newline