Materials Science Forum Vol. 969

Abstract: Thermo-mechanical treatment, in particular, cryo-rolling is a unique technique to produce super high strength AA-7xxx aluminium alloys with ultra-fine grained structure. In order to conduct the rolling at room temperature and cryo-temperature (liquid N₂ (-190°C)), the AA-7xxx alloy ingot was rolled from 6mm to 1mm with 85% reduction in thickness. Optical microscopy, XRD, electron microscopy, hardness and tensile testing were conducted on the rolled alloy for understanding the phase changes and evaluating the mechanical properties. The alloy rolled at liquid nitrogen (LN₂) exhibits very high strength with reasonable ductility. Corrosion behaviour of AA-7xxx series aluminium alloy various conditions in NaCl (3.5%) solution were investigated. Cold rolled and cryo rolled alloy exhibits better corrosion resistance than that of cast.

Abstract: An attempt was made to synthesis Al-5083alloy through high energy ball milling and densification through ECAP. The elemental powders consisting of Al5083 was milled for 5, 10 and 15 hrs using Retsch high energy ball mill (PM400). The physical and structural properties of mechanically alloyed particulates were characterised by diffraction methods and electron microscopy. The 15hrs nanocrystalline structured particulates of Al5083 alloy shows crystallite size of 15nm. Scanning Electron Microscope (SEM) reveals the morphology of alloy which is irregular shaped. The size of alloyed particulates also measured using SEM and found to be 7μm for 15hrs of milling. The 15hr milled alloy particulates were densified by ECAP through 90^o die channel angle. Maximum densification of 92% and highest hardness of 63HRB was achieved for sample consolidated with route-A for two passes along with sintering.

Abstract: The tribological characteristics of Electroless Ni-P and Ni-P/D (diamond) coatings were studied and analysed against AISI 52100 steel ball under dry reciprocating sliding conditions. Low and High Phosphorus Ni-P alloy coatings were deposited on steel substrate by Electroless deposition technique. Diamond particles were successfully reinforced into Ni-P matrix to produce Ni-P/D composite coatings. All coatings were subjected to heat treatment at 400^°. The micro-hardness, surface features and elemental composition of the coatings was analysed. The surface morphology of Ni-P and Ni-P/D coatings is detailed. Presence of dia mond particles in Ni-P matrix was confirmed by EDS analysis. Dry sliding wear tests showed a significant enhancement in wear resistance of Ni-P/D composite coatings compared to Ni-P coatings. Experimental results indicate that combined effect of diamond particles reinforcement and heat treatment play a crucial role in modifying the surface characteristics and tribological performance of the Ni-P coatings.

Abstract: Fracture energy (G_f) studies provide us with means to assess the variation in ductility of concrete. This paper presents the results of fracture energy studies conducted on 18 mixes of M60 Grade concrete consisting of rubcrete (0%, 5%, 10%, 15% of crumb rubber), steel fibre reinforced rubcrete (0.25%, 0.5%, 0.75%, 1% steel fibres and 0% and 15% crumb rubber) and polypropylene fibre reinforced rubcrete (0.1%, 0.2%, 0.3% polypropylene fibres and 0% and 15% crumb rubber) using three-point bend beam tests on 60 × 100 × 500 mm specimens as per TC 50 FMC (1985). Results indicated an enhancement of fracture energy with an increase in rubber content.

Abstract: High-temperature wear and friction properties of ZE41 alloy were evaluated using a pin on disc tribometer. The microstructure of the alloy has the equiaxed grains of 72±20µm decorated with the rare earth rich precipitates. Result shows that wear rate decreases upto 100°C and then increases until 250°C for all the loading conditions. The wear mechanism study revealed that the underlying thin oxide tribolayer minimizes the wear rate upto 100°C. Above 100°C, thickening of oxide layer due to enhanced oxidation rate results in breakage of the layer. Further, the increase of temperature softens the alloy which deforms and fractures in the subsurface at low critical load resulting in more delamination wear. The combined effects of oxidation and delamination wear are accentuated with the increase of load and temperature resulting in the increase of the wear rate. Comparing the influence of load and temperature on the wear rate, contact load is more.

Abstract: The experimatal alloys were aged at different temperatures of 180°C, 200°C, 220°C, and 240º C with calcium addition levels of (X=0.5, 1, 1.5, 2%) on Mg-6Al-1Zn-XCa alloy were investigated in 3.5% NaCl solution. All the experimatal alloys were immersed in 3.5% NaCl solutions and the resulted surface were analyzed to study the corrosion behaviour and its surface topography by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersed spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The result shows that corrosion attack occurred predominantly on ß phase and α phase exhibit relatively minor corrosion. In addition to that the increased aging temperature coarsens the intermetallic as well as α- Mg grains, which shows adverse effect to corrosion resistances and the best result were obtained at composition of 0.5wt.% Ca aged at 200°C.

Abstract: High entropy alloy (HEA) is a new class of alloy that has a different alloy design concept over the conventional dilute alloys. In this alloy, the alloying elements have an equi-atomic ratio that helps to increase the entropy of the alloy to stabilize the simple solid solution (BCC, FCC and HCP) over the intermetallics. The stabilization of solid solution improves the paradoxial properties such as strength and toughness. High thermal stability, excellent creep and fatigue properties, outstanding corrosion resistance are the attractive features of HEA. Recently, the HEA is explored as a matrix or particle in the metal matrix composites. Research studies on HEA based composites are plenty and scattered. In this work, we attempt to collate essential information in the HEA based composites. The overview covers (1) processing techniques, (2) microstructure characterization and (3) the mechanical properties in detail. A short note on the potential applications of HEA based composites is also proposed.

Abstract: The study presents the results of the investigation on the effect of soaking time on the, Crystalline structure and morphological properties of annealed EN-47 Spring Steel. The EN-47 Spring Steel samples were heated at 860 °C for soaking times of 60, 120, 240, 480 minutes. SEM analysis and XRD analysis were carried out to determine the morphology and crystalline phase of the material with increasing soaking time. Interatomic Distances also decreased with increased in soaking time. The sample with the Soaking time of 480 minutes exhibits a higher Interatomic Distance because of Formation of bigger grains. Through X-ray Diffraction transformation of the crystalline structure were analyzed, in that it is observed that Iron did not undergo any crystalline structure transformation with respect to soaking time whereas other elements changed their structure. Keywords: EN-47, Annealing, XRD, Crystalline Structure, SEM.

Abstract: The Al2014 alloy is extensively used as a structural material in aerospace industry and also it is proving to fit as wear resistant materials especially in sliding wear applications. In the present paper, the wear analysis of hybrid Al-MMCs utilising Al2014 alloy as matrix and Silicon carbide (SiC) / Graphite (Gr) particulate reinforcements was studied by changing load, speed and percentage reinforcement. Al2014+10%SiC composites and Al2014/(5%SiC+5%Gr) were prepared using liquid state processing. The wear test is carried out by using pin on disc with sliding speeds range from 0.84-1.67m/s and loads from 25-75N and sliding distance of 1000m.The outcomes demonstrated that the connected load had positive effect on wear rate while sliding rate indicates reverse movement on wear rate. The incorporation of SiC and Gr is observed to be significant on account of self-lubricating impact of Gr and resistance to material plastic flow due to SiC reinforcement.

Abstract: This work investigates the complete analytical solution for functionally graded material (FGM) plates incorporated with smart material. The odjective of the present work is to determine bending characteristics of piezoelectric FGM plates with different geometrical parameters, voltages and boundary conditions for electro-mechanical loading. In this work an analytical formulation based on higher order shear deformation theory (HSDT) is presented for the piezoelectric FGM plates. The solutions are obtained in closed from using Navier’s technique for piezoelectric FGM plates a specific type of simply supported boundary conditions and pc code have been developed to find out the deflections and stresses for various parameters. All the solutions are plotted against aspect proportion, side to thickness proportion as a function of material variety parameter (n) and thickness coordinate for different voltages. The significant trends from the results are obtained.