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Showing 4 results for Thermal Analysis
PREPARATION AND SINTERING OF W-20%Wt Cu COMPOSITE POWDERS PRODUCED BY CO-PRECIPITATION METHOD
M. Ardestani,, H. Razavizadeh,, H. Arabi, H. R. Rezaie,
Volume 6, Issue 2 (6-2009)
Abstract

Abstract:

materials can be fabricated by sintering of W-Cu composite powders. In this research W-20%wt Cu composite powders

was synthesized via a co-precipitation method. Precipitate obtained from a mixture of copper nitrate and ammonium

paratungstate (APT) in distilled water contained W-Cu compounds. This precipitate was washed, dried and calcined

at 550

of dried precipitate powder was determined by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray

diffraction (XRD). The sintering of the reduced powders was investigated as a function of temperature. Relative density

of more than 98% obtained for the powders sintered at 1200

close to theoretical calculations. The hardness of the sintered powders was 320 Vickers.

W-Cu composites are widely used as contacts, heat sinks and electro discharge electrodes. These kinds of°C in air and then reduced in H2 atmosphere in order to convert to W-Cu powders. The calcination temperature°C . The corresponding electrical conductivity was too
EXPERIMENTALl ANALYSIS OF PARTITION COEFFICIENT IN Al-Mg ALLOYS
M.h. Avazkonandeh-Gharavo, M. . Haddad-Sabzevar, H. Fredriksson,
Volume 13, Issue 2 (6-2016)
Abstract

Because the partition coefficient is one of the most important parameters affecting microsegregation, the aim of this research is to experimentally analyse the partition coefficient in Al-Mg alloys. In order to experimentally measure the partition coefficient, a series of quenching experiments during solidification were carried out. For this purpose binary Al-Mg alloys containing 6.7 and 10.2 wt-% Mg were melted and solidified in a DTA furnace capable of quenching samples during solidification. Cooling rates of 0.5 and 5 K/min were used and samples were quenched from predetermined temperatures during solidification. The fractions and compositions of the phases were measured by quantitative metallography and SEM/EDX analyses, respectively. These results were used to measure the experimental partition coefficients. The resultant partition coefficients were used to model the concentration profile in the primary phase and the results were compared with equilibrium calculations and experimental profiles. The results of calculations based on the experimental partition coefficients show better consistency with experimental concentration profiles than the equilibrium calculations.

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Modification of Primary Si Crystals and Fe-rich Intermetallics in LM28 Al Alloy Fabricated Through Thixoforming
B. Sharif, H. Saghafian, H. Razavi,
Volume 15, Issue 2 (6-2018)
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

Assessment of the Microstructure and Solidification Characteristics of Al–20%Mg2Si Composite under Melt Superheating Treatment Using Thermal Analysis
Saeed G. Shabestari, Sahar Ashkvary, Farnaz Yavari,
Volume 18, Issue 3 (9-2021)
Abstract
The influence of melt superheating treatment on the solidification characteristics and microstructure of Al–20%Mg2Si in-situ composite has been investigated. The results revealed that melt superheating temperature has a significant effect on solidification parameters and morphology of primary Mg2Si particles. Solidification parameters acquired using cooling curve thermal analysis method, indicate that both nucleation temperature and nucleation undercooling of primary Mg2Si particles increase by increasing melt superheating temperature, while recalescence undercooling decrease under the same condition. Also, based on the microstructural evaluations, melt superheating treatment can refine primary Mg2Si particles and alter their morphology from dendritic shape to more spherical shape and the eutectic microstructure of a-Al + Mg2Si becomes finer and the distance between eutectic layers becomes smaller.
 

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