Phase Transformation in the Ball Milled Fe_(31)Co_(31)Nb_(8)B_(30) Powders

作     者：S.Azzaza S.Alleg J.J.Sunol 

作者机构：Laboratoire de Magnetisme et Spectroscopie des Solides(LM2S)Departement de PhysiqueFaculte des SciencesUniversite Badji MokhtarAnnabaAlgerie Department de FisicaUniversitat de GironaGironaSpain 

出 版 物：《Advances in Materials Physics and Chemistry》 (材料物理与化学进展（英文）)

年 卷 期：2013年第3卷第1期

页      面：90-100页

学科分类：07[理学] 0703[理学-化学] 

主　　题：Nanomaterials Mechanical Alloying X-Ray Diffraction Fe-Co-Nb-B System Amorphization Kinetics 

摘      要：The mechanical alloying process has been used to prepare nanostructured Fe31Co31Nb8B30 (wt%) alloy from pure elemental powders in a high energy planetary ball-mill Retsch PM400. Microstructural changes, phase transformation and kinetics were studied by X-ray diffraction, differential scanning calorimetry and M?ssbauer spectrometry. The crystallite size reduction down the nanometer scale (~8 nm) is accompanied by the introduction of internal strains up to 1.8% (root-mean square strain, rms). Further milling time leads to the formation of partially paramagnetic amorphous structure in which bcc FeCo nanograins are embedded. The kinetics of amorphization during the milling process can be described by two regimes characterized by different values of the Avrami parameter n1 = 1.41 and n2 = 0.34. The excess enthalpy due to the high density of defects is released at temperatures below 300°C. The glass transition temperature increases with increasing milling time.