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Showing 7 results for Saghafian

Saghafian Larijani H., Rainforth W. M.,
Volume 1, Issue 3 (Apr 2004)
Abstract

An AI-7wt%Si-5vol%TiCp was worn against a cast iron disc in a tri-pin-on-disc machine, under dry sliding conditions at the sliding speed of 0.24 m/s and applied loads of 6, 20 and 40 N/pin. Stress-strain (`3-^9) curves were constructed by measuring the microhardness and the equivalent strain gradients in near surface regions on the cross-sectional surface prepared parallel to sliding direction.It was shown that, both the magnitude of plastic strains and the depth of plastic deformed zones increased with the applied load. The material exhibited considerable work softening in addition to work hardening at the highest applied load. The softened layer placed just beneath the mechanical mixed layer (MML), was mostly covered with the fine fractured eutectic Si and TiC fragments most of which were associated with microcracks at Al/Si and Al/TiC interfaces. The results were discussed in terms of some of the current work hardening models.
A.nouri, Sh.kheirandish, H. Saghafian,
Volume 5, Issue 4 (Autumn 2008 2008)
Abstract

Abstract: In the current work, the strain hardening behavior of dual-phase steels with different silicon content (0.34- 2.26 Wt. %) was examined using the modified Crussard-Jaoul analysis. It was shown that these dual-phase steels deform in two stages over a uniform strain range. Each stage exhibited a different strain hardening exponent varying with silicon content. At the first stage, work hardening exponent remind significantly constant, while during the second stage, it decreased with increasing silicon content from 0.34% to 1.51% and then increased for the higher silicon contents (1.51% to 2.26%). It was found that the strain hardening behavior of these steels was predominantly affected by the volume fraction of martensite at low silicon contet and the ferrite strengthening induced by silicon at the higher silicon content. The effect of silicon content on the volume fraction of martensite and tensile properties were also considered.
H. Mohammadzade, Sh. Kheirandish, H. Saghafian,
Volume 6, Issue 2 (Spring 2009 2009)
Abstract

Abstract:

transition and heat affected zones formed during surface remelting (in order to improve wear resistance) with TIG

process has been investigated. Relationship between various TIG parameters and thickness of remelted and heat

affected zones revealed that a high concentrated heat energy is imposed by TIG process which makes it a proper option

for focused surface treatment. Based on microstructural examinations five areas with different microstructure and

microhardness were identified within the surface area. Graphite flakes were totally dissolved within the first area

leading to the transformation of denderitic austenite to plate martensite and the formation of ledeburite within

interdenderites. The main feature of the second area, resulted from the presence of graphite flakes, was the local

melting with a gap in the vicinity of graphite flakes and that of third area was the formation of finer and denser

martensite plates closer to the graphite flakes compared with those formed at a further distance. In the fourth layer

there is a mixture of martensitic and pearlitic matrix while the matrix of fifth layer has no change of microstructure.

In this study the effect of graphite flakes present in a pearlitic grey cast iron on the microstructure of melted,

A. Noorian, Sh. Kheirandish, H. Saghafian,
Volume 7, Issue 2 (Spring 2010 2010)
Abstract

Abstract:

mechanical properties of AISIH 13 hot-work tool steel have been studied. Cast samples made of the modified new steel were homogenized and austenitized at different conditions, followed by tempering at the specified temperature ranges. Hardness, red hardness, three point bending test and Charpy impact test were carried out to evaluate the mechanical properties together with characterizing the microstructure of the modified steel using scanning electron microscope. The results show that niobium addition modifies the cast structure of Nb–alloyed steel, and increases its maximum hardness. It was found that bending strength bending strain, impact strength, and red hardness of the modified cast steel are also higher than those of the cast H13 steel, and lower than those of the wrought H13 steel.

In this research, the effects of partially replacing of vanadium and molybdenum with niobium on the
Khodamorad Abbaszadeh, Shahram Kheirandish, Hassan Saghafian,
Volume 7, Issue 3 (summer 2010 2010)
Abstract

The effects of lower bainite volume fraction on tensile and impact properties of D6AC ultrahigh strength steel were studied in the current work. To obtain mixed microstructures containing martensite and different volume fractions of the lower bainite, specimens were austenitized at 910° C, then quenched in a salt bath of 330°C for different holding times, finally quenched in oil. In order to obtain fully martensitic and bainitic microstructures, direct oil quenching and isothermal transformation heat treatment for 24 hours were used respectively. All specimens were double tempered at 200°C for 2 hours per tempered. Microstructures were examined by optical and scanning electron microscopes. Fracture morphologies were studied by scanning electron microscopy (SEM). Results showed that both yield and ultimate tensile strength generally decreased with an increase in volume fraction of lower bainite. However, a few exceptions were observed in the mixed microstructures containing 12% lower bainite, showing a higher strength than the fully martensitic microstructure. This can be explained on the basis of two factors. The first is an increase in the strength of martensite due to the partitioning of the prior austenite grains by lower bainite resulting in the refinement of martensite substructures. The second is a plastic constraint effect leading to an enhanced strength of lower bainite by the surrounding relatively rigid martensite. Charpy V-notch impact energy and ductility is improved with increasing the volume fraction of lower bainite.
B. Sharif, H. Saghafian, H. Razavi,
Volume 15, Issue 2 (June 2018)
Abstract

In the present research, thixoforming route was carried out in order to enhance the microstructural features of LM28 piston alloy. Typical microstructure of this alloy was composed of coarse, polygonal primary silicon particles, eutectic matrix and intermetallic phases. Thermal analysis was carried out to study the solidification path of the base alloy and determine the major arrest temperatures of metallurgical reactions. Continuous and iso-thermal mechanical stirring were utilized to produce non-dendritic LM28 alloy feedstock for further processing. The rheocast samples were subjected to a rotation speed of 450 rpm. The slugs machined from the solidified rheocast specimens were heated in the mushy zone temperature and then were thixoformed via a laboratory press. The thixoformed specimens show a relatively homogenous microstructure and present no evidence of porosities. Fine, blocky primary silicon and Fe-rich intermetallic particles were uniformly distributed in the matrix of LM28 alloy. Optical microscope and scanning electron microscope linked with EDX were used to investigate the microstructure of specimens

S. Mirzaei, H. Saghafian, A. Beitollahi, J. Świerczek, P. Tiberto,
Volume 16, Issue 3 (September 2019)
Abstract

In the present research, rapidly solidified Fe85.3B11P3Cu0.7 ribbons were prepared by melt spinning process. The microstructural variation as well as magnetic properties of the as-spun and annealed ribbons were characterized by X-ray diffraction (XRD), transmission Mossbauer spectroscopy and alternating gradient field magnetometer (AGFM). The results show two separated distinct exothermic peaks during heating resulting from the phase transition from amorphous to α-Fe and then to Fe3B, respectively. The study of magnetic properties in the amorphous and nanocrystalline states revealed that annealing the amorphous ribbons at 440˚C for 10 minutes gives rise to a significant increase in saturation magnetization (220 emu/g) which makes this alloy a good candidate for power applications.

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