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Showing 2 results for Seifollahi
The Effect of Mg on Microstructure and High Temperature Mechanical Properties of Hasteloy X Superalloy
A. Panahi Moghadam, M. Seifollahi, S. M. Abbasi, S. M. Ghazi Mirsaeed,
Volume 37, Issue 2 (Journal of Advanced Materials-Summer 2018)
Abstract
This paper was concerned with the effect of Mg on the temperature mechanical behavior and evaluation of the microstructure. The results showed that with increasing Mg from 0 to 47 ppm, the grain size was reduced from 64 to 38 µm and the carbides volume fraction was raised from 2.2 to 4.6 vot%. Mg changed the morphology of the carbide from a coarse and continuous one to a separate one. Mg with the mechanisms of grain boundary and matrix/carbide boundary led to changing the carbide composition and also, the mechanical properties. Mg increment from 0 to 47 ppm caused the enhancement of yield strength and rupture life from 309 to 345 MPa and from 16h to 30h, respectively. Grain size and the amount of carbide were the main factors contributing to the rupture of life properties in this study. The increment of the carbide volume fraction was the main mechanism of rupture life enhancement.

EFFECT OF MISH METAL TYPE ON THE MICROSTRUCTURE AND ABSORPTION/DESORPTION CHARACTERISTICS OF MMNI5 HYDROGEN STORAGE ALLOY
M. Judaki, M. Seifollahi, S. M. Abbasi, S. M. Ghazi Mir Saeed,
Volume 40, Issue 1 (Journal of Advanced Materials-Spring 2021)
Abstract
In this article, the effects of Pr and Nd were investigated on the microstructure and absorption/desorption characteristics of MmNi5 hydrogen storage alloy. The alloys were prepared in Vacuum induction furnace and the microstructures and phases were analyzed using scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDS) and X-ray diffraction (XRD). Hydrogen absorption/desorption characteristics was performed on Sievert apparatus. The results showed that the microstructure of the alloys consist of matrix, second phase as a result of Al segregation, porosities and cracks. The amount of second phases and Al in this phase in Mm(Pr,Nd)Ni4.7Al0.3  is less than MmNi4.7Al0.3. Al in Mm(Pr,Nd)Ni4.7Al0.3 were more homogenized. Pressure-Composition Isotherms of hydrogen absorption/desorption at 25˚C showed that for MmNi4.7Al0.3 and  Mm(Nd,Pr)Ni4.7Al0.3, absorption pressures were 14.52 and 9.90 bar,  desorption pressures were 5.53 and 5.49 bar, hydrogen storage capacities were 1.37 and 1.33 wt. % and hysteresis were 0.73 and 0.58, respectively. These results are useful in industrial applications, because of inconsiderable decrease in hydrogen storage capacity and the other positive variation in absorption/desorption characteristics, especially the hysteresis and absorption pressure.

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