Mechanical behavior of A356 matrix nanocomposites fabricated using two step mixing via stir casting technique
In this work an investigation of compressive strength and forgeability behavior have been made to explore the effect of SiC nano particles on A356 alloy matrix for the development of A356/SiC nanocomposites using two step mixing through stir casting technique. A356 alloy ingot was selected as a matrix and AFP+SiCn (99.9% pure aluminium fine powder+nano size SiC mechanically forged by using ball mill at 100 rpm for duration of 10 hours) as a reinforcement. Argon gas was used to protect from oxidation during ball milling process. SiC nano particles were varied from 1% to 5% in a step of 1% by weight. In stir casting technique, stirring process was performed at 500±50 rpm for mixing AFP+SiCn in the melt matrix for total stirring period of 10 minutes in two steps. Composites were poured at 680±20° C into the permanent mould. Compressive strength and forgeability tests of fabricated nanocomposites were evaluated by using hydraulic pellet press machine. To analyze the fractured mechanism SEM microstructure was examined. The presence of SiC nano particles were confirmed by EDX spectrum. It was revealed from the results that compressive strength increases with increment of SiC nano particles and found as 603 MPa at 5% SiC nano particles. Whereas forgeability of the nanocomposites were decreased with the increment of SiC nano particles. SEM micrographs showed the ductile fractured mechanism was dominant over the brittle fracture. The main constituents present in the nanocomposites were verified by EDX spectrum.
OF Al-SiC p COMPOSITES THROUGH POWDER Metallurgy Process and Testing Of Properties
Metal matrix composites are the class of composite materials finding vast applications in automotive, aircraft, defense, sports and appliance industries. A horizontal ball mill has been fabricated for milling of aluminum and SiC particles. The change in powder particle morphology during mechanical alloying of Aluminum and SiC powders using horizontal ball mill was studied. Al-SiCp composites with 5 to 30 weight % of SiCp were fabricated using powder metallurgy process. The various properties viz. hardness, density, porosity, compressive strength, indirect tensile strength and surface roughness were measured. The density, porosity, hardness, compressive strength and indirect tensile strength of Al-SiCp composites were found to increase with increase in the wt. % of SiCp from 5 to 30 weight percent. Mechanical alloying of powders resulted in improvement in hardness and compressive strength of Al-SiCp composites with 5 to 30 weight % of SiCp. The microstructure of polished and etched surfaces of powder metal Al-SiCp composite samples was studied using scanning electron microscope.
Physical Ageing of the Research Reactor Core Structural Materials Due to Neutron Irradiation Exposure: a Review
A research reactor (RR) is a  nuclear reactor that has function to generate and utilize neutron flux and radiation ionization for  research purposes and industrial applications. More than 60% of current operating RRs have  been operated for 30 years or more. As the time passes, the functional capabilities of structures,  systems and components (SSCs) of those RRs deteriorate by physical ageing, which can be  caused by neutron irradiation exposure such as irradiation induced dislocation and  microstructural changes. To extend the lifetime and/or to avoid unplanned outages, ageing on  the safety related SSCs of RRs need to be properly managed. An ageing management is a  strategy to engineer, operate, maintenance, and control SSC degradation within acceptable limits. The purpose of this study is to review physical ageing of the core structural materials of  the RRs caused by neutron irradiation exposure. In order to achieve this objective, a wide range  of literatures are reviewed. Comprehensive discussions on irradiation behaviors are limited only  on reactor vessel and core support structure materials made from zirconium and beryllium as  well as their alloys, which are widely used in RRs. It is found that the stability of the mechanical  properties of zirconium and beryllium as well as their alloys was mostly affected by the neutron  fluences and temperatures.