Keywords : mechanical alloying

Thermal plasma spheroidization of Nb-16Si powder alloy obtained by mechanical alloying

Nikolay G. Razumov; Anatoly A. Popovich; Andrey V. Samokhin; Aleksei V. Grigoriev

Advanced Materials Letters, 2018, Volume 9, Issue 1, Pages 86-90
DOI: 10.5185/amlett.2018.7073

Spherical Nb-Si powder alloy is a perspective material to manufacture products for the aerospace industry by additive technologies. Nb-16Si (at.%) powder alloy was prepared by mechanical alloying from pure elemental powders using planetary ball mill Fritsch Pulverisette 4. Spheroidization was carried out on plasma generator based on thermal plasma arc generator with vortex discharge stabilization. Experimental results show that plasma spheroidizing of Nb-16Si powders obtained by mechanical alloying is possible. It is shown that after the spheroidization the particle surface is rough which indicates the cast structure of the material. Three phases having different optical contrast are revealed on microsections: Nb5Si3, Nb3Si and Nbss, which is confirmed by X-ray diffraction. It is shown that the main peaks in the X-ray graph after MA correspond to a solid solution of niobium with a cubic lattice and the parameter a = 0.333 nm, as well as niobium silicide Nb5Si3 with a hexagonal lattice (P63/m) a = 0.7536 nm and c = 0.5249 nm. After spheroidization the hexagonal lattice of niobium silicide Nb5Si3 is transformed into a tetragonal lattice (I4/m) with the parameter a = 0.6557 nm and c = 1.186 nm. The other phase components remain unchanged.

Effect of heat treatment on the structure and magnetic properties of Sm-Fe alloys obtained by mechanical alloying

Nikolay G. Razumov; Aleksandr S. Verevkin; Anatoly A. Popovich

Advanced Materials Letters, 2017, Volume 8, Issue 5, Pages 673-677
DOI: 10.5185/amlett.2017.7071

The effect of heat treatment on the structure and magnetic properties of Sm-Fe alloys obtained by mechanical alloying was investigated. The crystallization temperature of Sm2Fe17, an amorphous alloy obtained by mechanical alloying, was determined using differential scanning calorimetry. Based on these results, various samples were annealed at different isothermal holding temperatures, and those with the best magnetic properties were found. Experimental studies show that decreasing the isothermal holding temperature from 750 °C to 630 °C increases magnetic characteristics nearly four times. The saturation magnetization, romance and coercivity of the Sm2Fe17 powder were 121 emu/g, 28.5 emu/g and 800 Oe, respectively. 

Microstructural And Phase Analysis Of Al Based Bulk Metallic Glass Synthesized By Mechanical alloying And Consecutive Spark Plasma Sintering With Varying Consolidation Pressure  

Ram S. Maurya; Ashutosh Sahu; Tapas Laha

Advanced Materials Letters, 2016, Volume 7, Issue 3, Pages 187-191
DOI: 10.5185/amlett.2016.6174

In the present work, Al86Ni8Y6 and Al86Ni8La6 powder blends were mechanically alloyed. Al86Ni8Y6 yielded full amorphous structure (150 h); whereas Al86Ni8La6 was partially amorphized after same duration of milling attributed to incomplete dissolution of solute ‘La’ in solvent ‘Al’. DSC experiment showed wider glass transition temperature range of ~ 44 o C (Tx - Tg = 268 o C-224 o C) in Al86Ni8Y6 amorphous powders; whereas no glass transition temperature was detected in Al86Ni8La6 powders. Further, Al86Ni8Y6 amorphous powders were consolidated via spark plasma sintering in the pressure range of 100-400 MPa. XRD and TEM analysis confirmed retention of larger fraction of amorphous phase in higher pressure sintered sample, attributed to suppression of mass transfer diffusion kinetics process. Higher pressure favored short range ordering leading to formation of various intermetallic phases; whereas comparatively faster diffusion in case of low pressure sintering promoted long range ordering forming nanocrystalline FCC-Al. Higher sintering pressure (say 400 MPa) consolidated sample resulted in better densification (~ 99 %) with improved inter-particle bonding and moreover, retention of larger volume fraction (~ 92 vol %) of amorphous phase with intermetallic nano-precipitates. Vickers microhardness test showed improvement in hardness with increasing sintering pressure attributed to higher fraction of retained amorphous phase and better inter-particle bonding.  

Dissolution Of Alloying Elements And Phase Formation In Powder Materials Fe-18Cr-8Ni-12Mn-xN During Mechanichal Alloying

Anatoly A. Popovich; Nikolay G. Razumov

Advanced Materials Letters, 2014, Volume 5, Issue 12, Pages 683-687
DOI: 10.5185/amlett.2014.6585

In this work, we investigated the effect of the treatment duration on the phase formation and dissolution of alloying elements in the process of mechanical alloying (MA) of iron with austenite forming elements in the nitrogen-containing atmosphere. The influence of MA parameters on the phase composition of the alloy showed the first of the alloying elements dissolved in the lattice of iron are nickel, then chrome and manganese. According to experimental data, the dissolution proceeds through the formation of a layered composite. Also the features of the nanocrystalline structure of powder materials Fe-18Cr-8Ni-12Mn-N, synthesized by mechanical alloying are presented. The nanocrystalline structure of these alloys consists of two structural components: grain-crystallites and grain boundary regions. Such type of structure corresponds to the Gleiter model. Dimensions of nanocrystals are in range from 6 to 20 nm.