Influence of Inoculant Type on the Microstructure Characteristics and Mechanical Properties of Ductile Iron

Transactions of the Indian Institute of Metals - The inoculation process of molten cast iron defines the final microstructure of the produced castings. The current study is concerned with the...     

Utilisation of red palm olein in formulating functional chocolate spread

Novel functional chocolate spreads were formulated by replacing butter fat in conventional chocolate spread by red palm olein at 20%, 40%, 60%, 80% and 100% levels. Sensory evaluation revealed that chocolate spread made from 20% red palm olein (RPOL) and 80% butter fat was accepted as the conventional chocolate spread (100% butter fat). Hence, the former two chocolate spreads were selected for further study. Samples were stored at room temperature and fridge for 6 months and monitored for their physical properties, fat stability, fatty acid composition and natural antioxidants.     

Influence of heat treatment conditions on the mechanical properties of Ti–6Al–4V alloy

In the current work, several heat treatments were carried out below and above the beta-transition temperature of the Ti–6Al–4V alloy followed by aging at 550 °C for 6 hours. The resultant microstructures and their effects on the mechanical properties of Ti–6Al–4V alloy were investigated. The results showed that solution treatment of Ti–6Al–4V samples followed by water quenching from β and α/β fields raised the alloy hardness from 380 to 575 and 656?HV, respectively, while no remarkable changes were observed after aging. The hot tensile strength of the as-forged sample increased from 671 to 756?MPa after water quenching from the ß- or α/ß- field, while the air cooling from β-phase field decreased the tensile strength to 644 MPa. The fracture mode of the tensile samples was more ductile in case of the solution-treated samples compared to the as-forged samples. A subsurface layer was formed due to the diffusion of oxygen into the surface at high temperatures. This layer which is known as ‘oxygen diffusion layer’ masked the differences of wear behaviour of the specimens.     

Wear of Al/Al3Zr functionally graded materials fabricated by centrifugal solid-particle method

In this study, Al–5mass%Zr functionally graded materials (FGMs) were fabricated by the centrifugal solid-particle method (CSPM) under applied centrifugal force of 30, 60 and 120G (units of gravity). Microstructural observation along the centrifugal force direction showed that Al₃Zr platelet particles are almost oriented normal to the applied centrifugal force direction. Volume fraction of Al₃Zr particles increases close to the ring surface. Moreover, this distribution range of Al₃Zr particles becomes broader with decreasing the applied centrifugal force. The wear anisotropy of the fabricated Al/Al₃Zr FGMs was strongly influenced by the platelet particles orientation at the test position. Investigating both of the worn surface morphology and the sub-worn surface layer showed that plastic deformation induced wear is the dominant mechanism during the wear process of Al/Al₃Zr FGMs samples. Therefore, some of the tested samples were severely deformed and an Al₃Zr particles-free layer containing Al–Zr supersaturated solid solution was observed very near to the worn surface during the wear test.     

Microstructural Effects on Corrosion Behavior of Investment Cast Ti-6.5Al-3.4Mo-1.7Zr Alloy

Abstract

Ti–6.5Al–3.4Mo–1.7Zr was cast as rods in a graphite mold using vacuum induction furnace. The cast rods were hot swaged then heat treated by using two regimes which resulted in fine and coarse lamella structures. The influence of these different structures on the corrosion behavior of α+β Ti-alloy samples was investigated. Potentiodynamic polarization in 3.5%NaCl solution showed that the swaged condition exhibited the highest corrosion resistance compared to the others. After isothermal oxidation for different times (2, 4, 8 and 16h), maximum weight gain was obtained after 8 h and the corrosion resistance of the swaged material was significantly higher than the other conditions. Thereby, isothermal oxidation enhanced markedly the corrosion resistance of the studied Ti-alloy. Among various conditions of the isothermally oxidized samples, the as-cast condition showed the highest value of pitting potential.     

Red Palm Olein: Characterization and Utilization in Formulating Novel Functional Biscuits

Functional biscuits were formulated by replacing white shortening (WS) by red palm olein (RPOL) at 20, 40, 60, 80 and 100%. Sensory evaluation of fresh biscuits indicated that all RPOL levels were significantly as acceptable as or superior to the control. Consequently, two superior RPOL levels (40 and 60%) were chosen for further investigation along with the control. Biscuits made from 40% WS + 60% RPOL exhibited significantly the lowest values regarding water loss during baking, volume before baking, specific volume, specific lightness, water activity and shearing force. Triacylglycerol and fatty acid composition of formulated biscuits resembled their counterparts for RPOL. These biscuits contained 1.8 times more tocopherols and tocotrienols and 10.4–14.8 times more carotenes than the control. Meanwhile, packaged biscuits were able to be stored at room temperature in the light for not less than 6 months without any deterioration in their quality.     

Influence of substrate composition on corrosion protection of sol–gel thin films on magnesium alloys in 0.6 M NaCl aqueous solution

The corrosion protection behaviour of organic–inorganic hybrid thin films on AZ31 and AZ61 magnesium alloy substrates has been studied. These films were prepared by a sol–gel dip-coating method. The organopolysiloxane precursors were γ-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethoxysilane (TMOS). An attempt was made to determine the possible relationships between the degradation of the sol–gel film and composition of the metal substrate during the exposure of the metal/coating system to 0.6 M NaCl aqueous solutions. For this purpose electrochemical impedance spectroscopy (EIS) and hydrogen evolution measurements were applied. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the sol–gel films formed on the surface of AZ61 alloy were far more perfect and uniform than those formed on the AZ31 alloy. This behaviour was attributed to the effect of the native oxide film initially present on the surface of the AZ61 alloy, which inhibited the attack of magnesium. Results indicated that the sol–gel coated AZ61 substrate tended to develop corrosion products slower than the sol–gel coated AZ31 substrate, trend that could change by prolonging exposure time. After 6 days of immersion, a clear inhibitive effect of the corrosion products formed during the test was observed in the case of the sol–gel coated AZ31, but not with the coated AZ61 alloy substrate, a phenomenon explained by the carbonate enrichment observed by XPS.     

Microstructure and Wear Behavior of Solidification Sonoprocessed B390 Hypereutectic Al-Si Alloy

The hypereutectic Al-Si alloys constitute an important family of alloys because of their excellent wear resistance and low thermal expansion. However, the optimal microstructure and hence the optimal service performance of these alloys cannot be achieved by the conventional melt treatments used in industry today, because of the chemical incompatibility between the primary-Si refiners and the eutectic-Si modifiers used in microstructure control. The current study aimed at using ultrasonic vibrations to improve the microstructure and the properties of these alloys. The results of the current study showed that for the B390 Al-Si alloy (i) the ultrasonic treatment has potential refining effect on the primary Si and Fe intermetallic phases, (ii) the primary Si particles become finer as the pouring temperature decreases from 1033 K (760 °C) to 938 K (665 °C), (iii) pouring and ultrasonic treatment at temperatures below the start of primary Si precipitation result in the coexistence of large and fine Si particles in microstructure, (iv) phosphorous additions of 50 ppm did not show any substantial effect in the ultrasonically treated ingots, (v) ultrasonic-treated samples have uniform hardness over the surface while the untreated samples show large scattering (high standard deviation) in hardness levels and (vi) ultrasonic-treated samples showed better wear resistance in the absence of phosphorous.