Showing 6 results for Mg
B. Saberpour, A. K. Taheri, J. M. Akhgar,
Volume 28, Issue 1 (6-2009)
Abstract
An Al-Mg-Si-Cu alloy was subjected to tensile testing, both under solutionized and ECAE-ed conditions, using strain rates of 10-4 s-1 to 10-1 s-1 at temperatures of 25 ˚C to 325 ˚C to investigate the dynamic strain aging (DSA) phenomenon in the alloy. Negative strain rate sensitivity (m) and increasing ultimate tensile stress were observed in the DSA region with increasing temperature . Regarding the activation energy of the phenomenon, it was suggested that the process is controlled by the interaction of Mg atoms with mobile dislocations at lower temperatures of DSA occurrence while at higher temperatures, the aggregation of Mg atoms and precipitates of a second phase decreases the amount of Mg atoms in the solid solution, resulting in the inverse DSA effect. Moreover, it was shown that at temperatures greater than 250 ˚C, the ratio of post-uniform to uniform elongation increases with increasing temperature or with decreasing strain rate due to the solute drag of Mg atoms in the Al matrix. Processing the alloy by ECAE transferred the negative m values to lower temperatures and decreased the tendency to DSA at higher temperatures. Calculating the mentioned ratio for the ECAE-ed specimens revealed that the post-uniform elongation dominates the uniform elongation at all examined temperatures and strain rates. Also, it was found that for ECAE-ed specimens, the ratio is not so sensitive to variations of temperature and strain rate.
A. Samadi, M. Ghayebloo ,
Volume 34, Issue 2 (7-2015)
Abstract
To evaluate the effect of inoculant addition on functionally graded microstructure of centrifugally cast Al-Mg2Si composites, two cylinders of Al-13.8 wt.% Mg2Si with and without the addition of 1 wt.% Al-5Ti-B inoculant were cast in a vertical centrifugal casting machine. The chemical composition, microstructures and microstructural phases of the different radial sections of the cast cylinders were studied using induction coupled plasma (ICP) method, optical/scanning electron microscopes, and X-ray diffractometry, respectively. The results showed that in the inoculant content cylinder, owing to the prevailing thermal regime as well as the specific mode of eutectic solidification in this composite, the titanium and boron compounds were segregated towards the middle layer of the cylinder and caused the formation of primary Mg2Si particles and non-eutectic Al () in this layer. In addition, due to the effect of centrifugal force during solidification, a higher volume fraction of the light primary Mg2Si particles, according to Stocks law, was segregated towards the inner layer of the cast cylinders.
M. Sarvari, M. Divandari,
Volume 35, Issue 2 (9-2016)
Abstract
In this study, centrifugal casting process was used for producing Al/Mg bimetal. Molten Mg was poured at 700 oC, with 1.5 and 3 melt-to-solid volume ratio (Vm/Vs) into the 450 oC preheated solid Al rotating at 800, 1200, 1600 and 2000 rpm. Castings were kept inside the centrifuged casting machine and cooled down to 150 oC. Investigating the effect of melt-to-solid volume ratio showed that increasing volume ratio from 1.5 to 3 results in diminishing metallurgical bonding in Al/Mg interface, because the force of contraction overcomes the resultant force acted on the interface. The results of study by scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) showed that bimetal compounds of Al3Mg2, Al12Mg17 and δ+Al12Mg17 eutectic structure (δ is the solid solution of Mg in Al) are formed in the interface. Atomic force microscopy (AFM) image of Al surface showed that the surface was rough in atomic dimentions, which can result in the formation of gas pores in the interface.
S.t. Mohammadi Benehi, S. Manouchehri, M.h. Yousefi,
Volume 35, Issue 3 (12-2016)
Abstract
Magnesium-manganese ferrite nanopowders (MgxMn1-xFe2O4, x=0.0 up to 1 with step 0.2) were prepared by coprecipitation method. The as-prepared samples were pressed with hydrolic press to form a pellet and were sintered in 900, 1050 and 1250˚C. Scanning Tunneling Microscope (STM) images showed the particle size of powders about 17 nm. The X-ray patterns confirmed the formation of cubic single phase spinel structure in samples sintered at 1250˚C. Substituting Mg2+ with Mn2+ in these samples, the lattice parameter decreased from 8.49 to 8.35Å and magnetization saturation decreased from 74.7 to 21.2emu/g. Also, coercity (HC ) increased from 5 to 23Oe and Curie temperature (TC ) increased from 269 to 392˚C. Samples with x= 0.2, 0.4, 0.6 sintered at 1250 ˚C, because of their magnetic properties, can be recommended for hyperthermia applications and for phase shifters.
F. Z. Akbarzadeh, M. Rajabi,
Volume 36, Issue 4 (3-2018)
Abstract
In this study, the composite material with composition of MgH2-10 wt% (25Ce-75Ni) has been prepared by co-milling of magnesium hydride powder with Ce-Ni alloy produced by vacuum arc remelting method. The effect of milling time and additive on magnesium hydride structure, i.e. crystallite size, lattice strain and particle size, and also hydrogen desorption properties of obtained composite were evaluated and compared with pure milled MgH2. It has been shown that the addition of 25Ce-75Ni alloy to magnesium hydride yielded a finer particle size. As a consequence, the desorption temperature of mechanically activated MgH2 decreased from 340 °C to 280 °C for composite 1(5 h mechanical alloying) and to 290 °C for composite 2 (15 h mechanical alloying). Further improvement in the hydrogen desorption tempreture of composite 1 can be related to finer particle size and higher Mg2NiH4 phase value, which corresponded with calculated enthalpy results.
A. Panahi Moghadam, M. Seifollahi, S. M. Abbasi, S. M. Ghazi Mirsaeed,
Volume 37, Issue 2 (9-2018)
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.
