Journal of Advanced Processes in Materials Engineering
Year:2012 | Volume:5 | Issue:4 (19)|Papers Count:8

Cobalt base ASTM F-75 casting alloy are widely used for manufacturing orthopedic implants. This alloy after casting needs both of homogenizing and solutionizing heat treatment and bioactivation of surface to increase ability of tissue bonding. In this investigation، ASTM F-75 casting substrate in the aim to solutionization and homogenization of microstructure and promote surface bioactivation was heat treated at 1220 °C for 1 hour in contact with hydroxyapatite- Bioglass powder. In order to in vitro evaluation، heat treated specimens were immersed in simulated body fluid (SBF). Surface of specimens before and after of immersion were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniqes. Results showed a homogeneous and appropriate microstructure with bioactive surfaces. Small ceramic agglomerates were observed on surface of specimens after heat treatment. In vitro results and formation of bone-like apatite layer on specimens indicated that heat treated samples were potentially suitable for bone replacement and tissue regeneration under highly loaded conditions.

b – sialon phase have gotten beneficial properties accompanied with several applications in the engineering fields. This phase could be synthesized using alominothermic reduction of aluminosilicates e.g. andalusite (Al2O3.SiO2) under the nitrogen atmosphere. Hence, in this investigation, the effect of heat treatment temperature on the quantity of b-sialon, Z value and unit cell parameters (a, c) has been investigated. Accordingly, 1523, 1623, 1723, 1823 and 1923K was utilized as the preferred temperatures. Also, aluminium and andalusite was composed in the ratio of 0.35 to 1. X-ray diffraction (XRD) technique was utilized for phase the determination of samples. Results of the investigation illustrated that the value of b-sialon and Z value were increased with enhancement of temperature. Also, there is a good liner relationship between unit cell (a, c) and Z parameters.

Metal foam have attractive a lot of attention in recent years due to their high strength-to-weight ratio and excellent energy absorption. Thus synthesis of Fe-10%Al foam with temporary space holder technique was studied in this research work. mixture of iron and Aluminum Powders were milled for 25 hours. Milled powders were characterized by XRD. NaCl was used as space holder and polyester resin as binder to fabricate foam sample. Samples morphology was investigated with optical microscopy and Scanning Electron Microscopy (SEM).The results show that Fe-10%Al foam up to 80% porosity can be produced was successfully with this method.

In this study, in order to produce intermetallic compound of MoSi2, pure molybdenum and silicon powders were milled using and attritor mill for 20 hrs with the molar ratio of Mo:Si being equal to 1:2. Mechanically alloyed powders were annealed in an atmosphere controlled furnace at 1100oC for different times. The result of X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated formation of pure MoSi2 which was achieved by mechanical alloying for 20 hr followed by annealing for 7hrs at 1100oC. Since the produced powders were extremely fine and not suitable for thermal spraying, they were agglomerated by carboxymethyl cellulose (CMC) binder and were meshed. This allowed a better flow of the powders and indicated a suitable flow for thermal spraing.

Machine parts can be produced by one of various manufacturing methods such as forging, machining, casting or welding methods. Choice of the manufacturing method depends on production costs of the alternatives for individual parts. Friction welding method as a mass production process is finding increasing industrial acceptance, particularly for joining dissimilar materials. Mechanical properties and micro-structure of the friction welding between two non-similar materials of CK35 and 18CrMo4 have been analyzed by using mechanical tests like tensile, bending and hardness, and microstructure analysis with scanning electron microscope and optical microscope. The results showed that the maximum tensile strength (576 MPa) and maximum bending angle without fracture (30 degree) is achieved in this condition: 13 seconds of pre-heating (friction time) and 3 seconds of forging time. The micro-structure analysis showed the presence of base material, HAZ, and thermo-mechanical region in both sides of friction welding. Meanwhile the maximum hardness is in the welded region.

In this research the properties of nanocomposite (poly 4-vinyle pyridine/Al-SBA-15) precursor in order to b-SiAlON formation by using Carbotermal Reduction and Nitridation (CRN) was investigated. Firstly the nanocomposite P4VP/Al-SBA-15 was synthesized and then fired under N2 atmosphere at 1450 oC with 10oC/min heating rate and soaking time (0, 6) hrs in order to b-SiAlON formation. To characterize, phase analysis (XRD), microstructure studies (SEM/TEM), 29Si, 27Al Magic Angls Spinning (MAS-NMR) specific surface areas (BET) and thermal analysis (DSC) were carried out on Al-SBA-15 and P4VP/Al-SBA-15 samples. Result of phase analysis investigation (XRD) showed that the mesoporous structure was formed and also confirmed by SEM/TEM studies by using. 27Al- NMR spectral the presence of Al in mesoporous structure (Al-SBA-15) was confirmed. Also changes in chemical shift (ppm) in 29Si-NMR spectral showed that the polymerization was done in good conditions on the surface of Al-SBA-15. Finally samples fired under N2 atmosphere and results showed that not only carbon amount, type of carbon and surface area of precursor were important factors but also considering the higher amount of carbon than stochumetric was unavoidable.

In this research, TiB2-TiC nanocomposite was performed through three different formulations (1): (Ti/B/C), (2): (Ti/B4C) and (3): (H3BO3/TiO2/Mg/C) by using of the MASHS process and the effect of the activation of starting materials on the final microstructure was investigated. The initial powder mixture was activated through mechanical milling and then was synthesized in a tube furnace (in 1100oC). The XRD and SEM analysis of the milled powder showed that in the mixture based on reaction (2) and (3), milling process could not full synthesis of TiC and TiB2 phases successfully and the combustion reaction had been necessary. While the reaction (1), milling for six hours for the synthesis of products was sufficient and it didn’t need to SHS reaction. The XRD and SEM analysis of the synthesized samples showed that if a mixture of the reaction (2) would pre-mill for 6 h, we found the best results. This value for the reaction (3) was 1 h.

Magnesium Oxychloride as known Sorel cement, has superior strength over the other cements, and is used as bonding agent in various commercial applications. The amount of the magnesium chloride varied from 0.5 to 1.9 moles and the cold crushing strength (CCS) of samples was measured. X-Ray diffraction (XRD) of matrix are investigated. The morphology and Microstructure of the phases are characterized using a scanning electron microscope (SEM). It is believed that a molar ratio of MgO/H2O of 13/12 and 1.5 moles of MgCl2.6H2O can produce a promising matrix composition for proper design.