Phase transformation during mechano-synthesis of nanocrystalline/amorphous Fe–32Mn–6Si alloys

Abstract

Mechano-synthesis of Fe-32Mn-6Si alloy by mechanical alloying of the elemental powder mixtures was evaluated by running the ball milling process under an inert argon gas atmosphere. In order to characterize the as-milled powders, powder sampling was performed at predetermined intervals from 0.5 to 192 h. X-ray florescence analyzer, X-ray diffraction, scanning electron microscope, and high resolution transmission electron microscope were utilized to investigate the chemical composition, structural evolution, morphological changes, and microstructure of the as-milled powders, respectively.According to the results, the nanocrystalline Fe-Mn-Si alloys were completely synthesized after 48 h of milling. Moreover, the formation of a considerable amount of amorphous phase during the milling process was indicated by quantitative X-ray diffraction analysis as well as high resolution transmission electron microscopy image and its selected area diffraction pattern. It was found that the α-to-γ and subsequently the amorphous-to-crystalline (especially martensite) phase transformation occurred by milling development. © 2013 Elsevier Inc. All rights reserved. Keywords:Fe-Mn-Si shape memory alloys Mechanical alloyingPhase transformation Nanostructural/amorphous phase Microstructure IntroductionFe-Mn-Si alloys are a class of smart materials due to their suitable shape memory effect (SME), excellent machinability and formability, low cost, good weldability and corrosion resistance, and high strength having several industrial applications such as dampers, pipe couplings, big shape memory devices, hard metals or alloys joining, oxygen blowing nozzles and so on [1][2][3][4][5][6][7][8][9][10][11]. The production of stress induced martensite (ε, hcp) from parent austenite phase (γ, fcc) and the reverse transformation (γ to ε) during the heating cycle are the origins of SME in this alloying system [12][13][14][15][16][17][18]. This non-thermoelastic or semi-thermoelastic conversion occurred by the creation of stacking faults (SFs) due to the movement of the Shockley partial dislocations (a γ /6 <112>) in the parent phase. SFs are suitable sites for nucleation of the martensite phase; eventually, the ε-phase can be formed by their overlap [12,[17][18][19][20][21][22][23].Although induction melting under an argon gas atmosphere is widely utilized to produce Fe-based SMAs, solid-state routes such as mechanical alloying (MA) can be used to produce the alloys in the powder form [24]. During MA, by applying the high energy collision between ball and particles and consequently the repeated cold welding and fracture of the powders, not only is the alloying process attained but also the synthesis of the non-equilibrium structures such as supersaturated solid solutions, nanocrystalline and amorphous structures, and intermetallic compounds is possible [24][25][26][27][28].Recently, MA has been widely used to synthesize nanocrystalline and amorphous SMAs [29][30][31], although limited investigations have been done on Fe-Mn-Si alloys.

Powder Metallurgy: An Alternative for FeMnSiCrNi Shape Memory Alloys Processing

“…These data suggest ε-hcp martensite is stressinduced during pre-straining while thermally induced α -bcc martensite is detwinned and reverts to γ-fcc austenite (Pricop et al, 2018). Similar results were obtained by Saito et al and Amini et al The former observed the formation of the γ-fcc and ε-hcp phases from the α-bcc phase due to diffusion of Mn and Si atoms into the Fe matrix (Saito et al, 2014) and the latter performed MA on Fe-32Mn-6Si and found that the α →γ phase transition occurred during the ball milling process (Amini et al, 2013).…”

Preparation of high crystalline nanoparticles of rare-earth based complex pervoskites and comparison of their structural and magnetic properties with bulk counterparts

“…Therefore, the microstrain of the synthesized samples was calculated using Williamson-Hall analysis [45] and the values are inserted in Table II. Like orthorhombic deformation, the micro-strain was also found to increase gradually with milling time [46] and for 12 h ball milling sample the microstrain is significantly higher.…”

Stress-Induced Dual-Phase Structure to Accelerate Degradation of the Fe Implant

“…In the presence of the Si element, the stacking fault energy (SFE) is reduced to enable the dislocations to tangle into stack faults, which act as suitable sites for martensite nucleation . In addition, MA-induced plastic deformation of materials supplies stress energy for the austenite → martensitic transformation . In this case, part of austenite transforms into the martensite phase.…”