Department of Materials Characterization and Selection (Metallurgy) (2014 - Present)
Metallurgy and Materials Engineering
, Iran University of Science and Technology,
Research field: Weding, Advanced Materials
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Phone: 021-82884908
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Dr Homam Naffakh-Moosavy was born in Tehran-Iran, 1983. He is now a faculty member of materials selection-Metallurgy at Tarbiat Modares University. He is working in the fields of additive manufacturing, welding, advanced materials for bio and energy.
Titanium alloys are commonly used in orthopedic devices due to their good corrosion resistance, high specific strength and excellent biological response. The direct contact between the implant surface and the host tissue results in notable effect of surface properties such as surface topography on the biological responses. The aim of this study is to investigate the effect of frequency of pulsed Nd-YAG laser on Ti6Al4V alloy surface topography and its influence on the improvement of biocompatibility while other laser parameters kept constant. The range of applied frequency values were selected from 1 to 20?Hz. The range of surface roughness was found between 452?nm and 3.37?μm. The untreated sample and also samples with the highest and the
The thermal regime and microstructural phenomenon are studied by using finite-element (FE) modelling and the analytical Rosenthal equation during laser welding of aluminum alloy 5456 (AA5456) components. A major goal is to determine the merits and demerits of this analytical equation which can be an alternative to FE analysis, and to evaluate the effect of imperative assumptions on predicted consequences. Using results from the analytical and numerical approaches in conjunction with experiments, different physical features are compared. In this study, the results obtained from experiments in terms of melt pool shapes are compared with the predicted ones achieved from the numerical and analytical approaches in which the FE model is more accu
In this work, surface mechanical attrition treatment (SMAT) was carried out on 316L stainless steel in order to study the effects of treatment parameters on the deformed depth and deformation mechanisms. Results showed that the residual stresses caused by collision of shots led to formation of martensite. Increase in treatment duration and shot size led to more martensite formation because of higher strains. An increasing hardness profile was also observed from the depth towards the surface in SMATed samples which was due to grain refinement, martensite formation and twinning. Strength of samples also was improved by SMAT so that the yield strength in the sample treated for 2 h by 6 mm shots was increased by 58 percent. In addition, Crussar
Predicting extreme limit states in steel structures using finite element simulations requires an understanding of the fracture mechanisms themselves and the relationship of various models to these mechanisms. Aiming at addressing dominant damage mechanisms in the Ultra-Low-Cycle Fatigue (ULCF) regime which occurs during earthquakes, circumferentially notched tensile bars were subjected to cyclic loadings with large displacement amplitudes. Two weld metals from rutile and basic classifications and two different grades of structural steels were selected to determine the role of microstructural features in the response of materials to ULCF conditions. Scanning Electron Microscopy (SEM) technique equipped with 3D measurement software was employ
In this study, Ni–Co–P multilayer coatings were deposited using pulse reverse current. Alternative Co/P-rich and Co/P-poor layers were fabricated by alternation of cathodic duty cycle at 20 and 90% values. The layer thickness was altered within 3000–90 nm range. Coatings evaluation involved investigation of microstructure and chemical composition, microhardness, fracture toughness, and tribological measurements. The results showed that the thinning the layers enhanced the microhardness by up to 700 Hv and improved cracking resistance. Tribological study indicated that decreasing the layer thickness resulted in the friction coefficient lower than 0.4 and decreasing the mass loss and changing the wear mechanism from delamination to co
It is observed that in laser welding of aluminum alloys, magnesium can evaporate, and the weld penetration is dependent on Mg content of the alloy and Mg loss from the weld pool. In this research, it is proposed that the presence of Mg not in the base metal alloy, but rather the presence of Mg vapor in the plasma plume over the weld pool affects the laser absorption, and it is through this phenomenon that the weld profile and penetration is affected. Numerical simulation was performed to determine the relationship between the weld profile to estimate the effective laser absorption coefficient of four Al alloys and in parallel EPMA technique was used to determine the Mg losses of the weld metals. The combined analysis of the results showed t
Pulsed Nd:YAG laser welding of 17-4 martensitic precipitation hardening (PH) stainless steel (SS) is investigated. In order to achieve optimum laser welding parameters, bead on plate (BOP) welding was conducted on 17-4 PH SS. No crack was detected in the weldments, and microstructure of weld metal was δ-ferrite in the martensite matrix. Resistance to cracking of weldment was correlated to the presence of δ-ferrite in the weld metal, and using pulsed Nd:YAG laser as a low heat input welding method. Four HAZs were distinguished and microstructure evaluation in each zone is discussed. In the second part of this research, pulsed Nd:YAG laser welding of similar 17-4 PH SS in butt joint configuration was performed. Microstructure characterizati
Kovar, due to its close thermal expansion coefficient to glass, can be used as a mediating alloy in joint of glass to metals such as AISI 304L. In the present research, the effect of parameters of pulsed laser on dissimilar welding of Kovar to AISI 304L has been investigated. For observation and investigation of the results, metallography, Energy dispersive X-ray spectroscopy (EDS) and microhardness tests have been used. Results obtained from microstructural examinations, indicated the existence of solidification crack and lack of complete mixing in the weld metal. According to the results, the heat input must have an optimum value equaling approximately 19.1 J/mm. At higher levels such as 32.6 J/mm, the TCL (total crack length) value r
Magnetic Pulse Welding (MPW) is an essential procedure for joining of dissimilar metals. The high velocity collision and jetting are the most important aspects of MPW controlled by welding parameters: discharge voltage and air gap. In this study, the collision surfaces and interface of MPW of pure Al and Cu are investigated. The effect of air gap on the bonding is studied by variation of the air gap from 0.7 to 4 mm. The collision surfaces of Cu and Al, the interface of welding and fracture surface were examined by optical microscope and SEM equipped with EDS analysis. The results revealed that the metallurgical bonding is obtained in the air gap of 0.7 mm, whereas higher air gaps (1 to 4 mm) result in debonding due to higher impact e
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