Muhammad Hussain Ismail

Formation of microporous NiTi by transient liquid phase sintering of elemental powders

Porous metallic structures are attractive for biomedical implant applications as their open porosity simultaneously improves the degree of fixation and decreases the mismatch in stiffness between bone and implant, improving bonding and reducing stress-shielding effects respectively. NiTi alloys exhibit both the shape memory effect and pseudoelasticity, and are of particular interest, though they pose substantial problems in their processing. This is because the shape memory and pseudoelastic behaviours are exceptionally sensitive to the presence of oxygen, and other minor changes in alloy chemistry. Thus in processing careful control of composition and contamination is vital. In this communication, we investigate these issues in a novel technique for producing porous NiTi parts via transient liquid phase sintering following metal injection moulding (MIM) of elemental Ni and Ti powders, and report a new mechanism for pore formation in the powder processing of metallic materials from elemental powders.

Characterization and Rheological Studies on Ready-Made Feedstock of Stainless Steel 316L in Metal Injection Molding (MIM) Process

Current trend for manufacturers associated to MIM industry try to enhance the feedstock in term of its characteristics, since it is the most crucial part of the MIM process. This paper covered the characterization and rheological studies on a ready-made feedstock of stainless steel 316L which is vital to determine the availability and suit the needs of many advanced applications. There are three different experiments involved which are Scanning Electron Microscope (SEM), Differential Scanning Calorimeter (DSC), Thermogravimetric (TGA) and Capillary Rheometer. Observation through SEM gives an insight of the bonding microstructure matrices of the feedstock and also determines the homogeneity of the feedstock. DSC testing defines the melting temperature of the 3 binders used which are 62.07°C for surfactant, 178.72°C for filler and 236.61°C for backbone binder. From TGA result, it showed that the total weight loss of feedstock was 39%. Throughout the capillary rheometer testing, the feedstocks viscosity was decreasing as the shear rate increasing. The feedstock exhibits pseudoplastic behaviour since its flow behaviour index was less than 1. It is founded that at the temperature of 190°C, the feedstock exhibits the best characteristics for injection.

Fabrication and characterisation of carbon fibre reinforced polymer rods with aluminium foam core

Abstract Carbon fibre reinforced polymer composites are high-performance materials that have become the dominant advanced composite materials used for aerospace, automobile, sporting goods and other applications owing to their high strength, high modulus and low density. In this study, a new fabrication technique of aluminium foam was employed where NaCl was used as the space holder and argon gas was injected into the aluminium molten metal. The NaCl particles were then removed by dissolution process. The aluminium foam specimens were then wrapped with carbon fibre pre-preg and cured in a vacuum oven. The compressive properties such as compressive strength, elastic modulus and failure strain were obtained from the analysis of stress-strain curves. The results showed that carbon fibre reinforced polymer composite tubes with aluminium foam core exhibited higher compressive strength and elastic modulus compared with neat aluminium foam rods and neat carbon fibre reinforced polymer rods.

Interaction between Binder and Powder in Injection Moulding of 316L Stainless Steel

Owing to several steps involved in metal injection moulding (MIM) process, it is important to understand the interactions between metal powder and binder mixture particularly during mixing, injection moulding and debinding. A polar organic compound generally forms hydrogen bonds more readily with metal powder because of acid-base interactions. In this study, the interaction of local binder system comprised of; palm stearin (PS) and thermoplastic natural rubber (TPNR) with conventional binder; polyethylene (PE), polypropylene (PP) and paraffin wax (PW) and mixed with 316L stainless steel powder were investigated. The results showed that all the binder have high interaction with 316L stainless steel that make, the resulting the bonding sufficiently strong and suitable for MIM process. Keywords: Chemical interaction, Injection Moulding, Binder, Rheology

Feedstock Characterization of Elemental Nickel and Titanium Powders Mixture for Metal Injection Moulding Process

The success of metal injection moulding (MIM) process is significantly influenced by the homogeneity level of the powder-binder mixture (feedstock). This paper highlights some initial characterization of the feedstock containing elemental Ni and Ti powders mixture, (50.8 at.% Ni/ 49.2 at.% Ti) mixed with Palm stearin-based binder system. The feedstock was prepared using an internal mixer, HAAKE Rheomix at a temperature of 160°C for 2 hours. The feedstock was then characterized by Differential Scanning Calorimetry (DSC), Thermogravimetric (TGA), Scanning Electron Microscopy (SEM) and Capillary Rheometer. All the results obtained were analyzed and discussed for further injection moulding process.

Microstructure and Mechanical Properties of Ti-15-3 Alloy Gas Tungsten Arc Welds Prepared Using CP-Titanium Filler

Strength and ductility of fusion zone of metastable β titanium alloy welds can be improved by choosing suitable fillers. This paper reports the effects of using CP-Ti filler on the microstructural and mechanical properties of Ti-15-3 weldments. Full penetration autogenous and CP-Ti filler welds were produced by pulsed gas tungsten arc welding. X-ray diffraction analysis revealed small amounts of α-Ti phase in the diffraction pattern obtained for welds prepared using CP-Ti filler. Transmission electron microscopy analysis showed presence of grain boundary and intragranular α in the fusion zone of the welds prepared using CP-Ti filler. The welds prepared with CP-Ti filler showed higher hardness, higher UTS and lower % strain compared to autogenous welds.

Grain Refinement, Microstructural and Hardness Investigation of C Added Ti-15-3 Alloys Prepared by Argon Arc Melting

Mechanical properties of as-cast beta titanium (β-Ti) alloy can be improved by grain refinement and formation of insoluble precipitate. This paper reports the effect of carbon (C) addition on microstructure and hardness of cast Ti–15V–3Cr–3Sn–3Al (Ti-15-3) samples prepared by argon arc melting. X-ray diffraction analysis of C added as cast Ti-15-3 samples revealed the presence of β-Ti and TiC phases. Scanning electron microscope analysis revealed eutectic TiC precipitates in C added Ti-15-3 samples while a reduction in grain size was observed with increasing carbon addition. Inoculation effect due to TiC and growth restriction by C for β phase resulted in decreased grain size. Hardness of C added Ti-15-3 alloys increased with the increased carbon content of the sample. The improvement in hardness was contributed by grain refinement and the formation of TiC precipitates in the samples.

Microstructures and mechanical properties of Ti-Nb alloy at different composition of Nb produced via powder metallurgy route

The aim of this study is to evaluate the effect of phase formation to the mechanical strength of Ti-Nb alloy produced by powder metallurgy (PM) process. Niobium (Nb) powder was added to the elemental titanium (Ti) powder by wt%, cold-compacted and sintered at 1200°C. The samples were characterized in term of shape and sizes of the particle, phases present, microstructures and compressive strength. XRD pattern showed that increasing Nb content resulted in increased beta-phases which also evidenced by a greater fraction of light gray-scale image in back-scattered SEM analysis. The alpha phase region almost eliminated in the 35 wt% Nb. The lowest compressive strength was observed in 45 wt% Nb is due to partly crystallized region in the microstructure observed. The alloy containing 35 wt% Nb exhibited better beta-phase structures in the matrix. The Young’s modulus of 13.46±2.44 GPa were obtained from 45 wt% Nb addition in the Ti alloy. All sintered samples are potential candidates for implant applications.

Biomechanical testing of bovine skin using various sample specifications

Abstract The main objective of this research is to perform the biomechanical testing on bovine skin. This paper attempts to highlight the success in determining the biomechanical properties and its comparison of three categories of bovine skin via experimental–numerical integration. Initially, four samples for each category of bovine skin were stretched using a mechanical tensile test machine (category 1: I-shape with hair; 2: I-shape shaved and 3: rectangular shape). Concurrently, a stress–stretch equation was re-derived based from the Ogdens constitutive equation and a Matlab Program was written as a tool to quantify the biomechanical properties. Finally, the findings show the Ogden constitutive parameters (biomechanical properties) in terms of μ (Pa) and α for the three categories I-shape with hair, I-shape-shaved and rectangular shape. The quantified values were (0·023 Pa, 17·78); (0·040 Pa, 13·55) and (0·029 Pa, 12·5), respectively. Thus, the results obtained were in close agreement with the results reported by other researchers.

Viscosity Analysis of Copper Powder Mixed with Palm Stearin Based Binder

In this experimental work, the viscosity of copper powder mixed with developed binder system based on palm stearin were studied and analyzed by means of rheological test. The feedstock is limited to 65 vol% of copper powder and 35 vol% of binder system; each of which consists of palm stearin (PS) and polyethylene (PE) prepared in four distinct formulations; 50 wt.% PS, 60 wt.% PS, 70 wt.% PS and 80 wt.% PS. Both copper powder and binder system were initially mixed to produce four sets of homogeneous feedstock. The rheological characterizations of the feedstock which includes its viscosity, pseudo-plasticity, shear sensitivity index (n), and yield stress were analyzed by using Rosand RH2000 Capillary Rheometer at a temperature of 150°C. Finally, the moulded parts were immersed in the n-heptane solution for 7 hours. The morphology analysis by Scanning Electron Microscope (SEM) by means of Hitachi SU 3500 Scanning Electron Microscope were carried out at the end of every stage. The study has shown clearly that PS plays several important roles in the composite binder system.