Showing 3 results for G. Shabestari
H. Momeni, H. Razavi, S. G. Shabestari,
Volume 8, Issue 2 (spring 2011 2011)
Abstract
Abstract: The supersolidus liquid phase sintering characteristics of commercial 2024 pre-alloyed powder was studied at different sintering conditions. Pre-alloyed 2024 aluminum alloy powder was produced via air atomizing process with particle size of less than 100 µm. The solidus and liquidus temperatures of the produced alloy were determined using differential thermal analysis (DTA). The sintering process was performed at various temperatures ranging from the solidus to liquidus temperatures in dry N2 gas atmosphere for 30 min in a tube furnace. The maximum density of the 2024 aluminum alloy was obtained at 610ºC which yields parts with a relative density of 98.8% of the theoretical density. The density of the sintered samples increased to the maximum 99.3% of the theoretical density with the addition of 0.1 wt. %Sn powder to the 2024 pre-alloyed powder. The maximum density was obtained at 15% liquid volume fraction for both powder mixtures.
M. Ghanbari, M. R. Aboutalebi, S. G. Shabestari,
Volume 11, Issue 2 (June 2014)
Abstract
Geometrical design of the spiral crystal selector can affect crystal orientation in the final single crystal
structure. To achieve a better understanding of conditions associated with the onset of crystal orientation in a spiral
crystal selector, temperature field was investigated using three-dimensional finite element method during the process.
Different geometries of spiral crystal selector were used to produce Al- 3 wt. % Cu alloy single crystal using a
Bridgman type furnace. The Crystal orientation of the samples was determined using electron backscattered
diffraction (EBSD) and optical microscopy. Analysing the temperature field in the crystal selector revealed that, the
orientation of growing dendrites against liquidus isotherm in the spiral selector was the reason for crystal
misorientation which differs in various selector geometries. Increasing the take-off angle from 35° up to 45° increases
the misorientation with respect to <001> direction. Further increase of take-off angle greater than 45° will decrease
the crystal misorientation again and the efficiency of the selector to produce a single grain is decreased.
Saeed G. Shabestari, Sahar Ashkvary, Farnaz Yavari,
Volume 18, Issue 3 (September 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.
