Mechanical properties and failure mechanisms of Mg-Zn-Y alloys with different extrusion ratio and LPSO volume fraction

In long period stacking ordered(LPSO)phase containing Mg-Zn-Y alloys,high elastic modulus and deformation kinks of LPSO phase considerably enhance the tensile yield strength,with slight detriment of or benefit to the ductility depending on its volume fraction.In present work,uniaxial tensile tests and fracture toughness tests are carried out using Mg99.2Zn0.2Y0.6,Mg97Zn1Y2,Mg89Zn4Y7 and Mg85Zn6Y9(at%)materials with different extrusion ratios.Extrusion processing enhances both strength and ductility due to the recrystallization of Mg grains.Variable plastic deformation mechanisms are activated depending on volume fraction of Mg and LPSO phase as well as their relative size during bending.{1012¯}<101¯1¯>tensile twins in Mg grains and deformation kinks in LPSO phase are observed,which dissipate large amount of deformation energy favoring for toughness.However,inherently brittle LPSO phase is detrimental to toughness.Microstructure-motivated empirical models for yield strength and fracture toughness prediction based on rule of mixtures are calibrated by experimental data.Energy release rates of individual mechanisms are estimated,which quantitatively indicate strong Mg/LPSO interaction.

Material Selection of a Natural Fibre Reinforced Polymer Composites using an Analytical Approach

Material selection has become a critical part of design for engineers,due to availability of diverse choice of materials that have similar properties and meet the product design specification.Implementation of statistical analysis alone makes it difficult to identify the ideal composition of the final composite.An integrated approach between statistical model and micromechanical model is desired.In this paper,resultant natural fibre and polymer matrix from previous study is used to estimate the mechanical properties such as density,Young’s modulus and tensile strength.Four levels of fibre loading are used to compare the optimum natural fibre reinforced polymer composite(NFRPC).The result from this analytical approach revealed that kenaf/polystyrene(PS)with 40%fibre loading is the ideal composite in automotive component application.It was found that the ideal composite score is 1.156 g/cm^(3),24.2 GPa and 413.4 MPa for density,Young’s modulus and tensile strength,respectively.A suggestion to increase the properties on Young’s modulus are also presented.This work proves that the statistical model is well incorporated with the analytical approach to choose the correct composite to use in automotive application.

Microstructure, Dislocation Density and Thermal Expansion Behavior Using Thermo Elastic Models of Zircon Sand Reinforced as Cast ZA-27 Composites

In the present work stir casting route is used to fabricate the ZA27 Metal matrix composites containing 3 wt%, 6 wt%, 9 wt%, and 12 wt%. Zircon sand particulates of size 100 mesh. Microstructure studies using Optical Microscopy, SEM-EDAX are carried out to ascertain the distribution and morphology of particulates in the composites. Effect of zircon sand as reinforcement on bulk density, porosity, of the fabricated composites is studied. SEM studies are carried out to understand the behavior of as-cast ZA27 alloy reinforced with zircon sand. The dislocation density of the fabricated composite affects the strength of the composites and depends on the strain due to thermal mismatch and is found to increase with increase in weight% of zircon sand. However, it does not consider casting defects of voids/clustering observed in micrographs of the fabricated composite. Porosity in composites does not have influence on Coefficient of thermal expansion (CTE) of the ZA27 composites studied using thermoelastic models like Kerner and turner model and rule of mixtures of composite.