Effect of Process Control Agents on Fe-15at.%Nb powder during Mechanical Alloying

Abstract

In this paper, Fe-15at.%Nb alloys were produced from high purity Fe (min. 99.8%) and Nb (min. 99.8%) powders via a mechanical alloying process. The effects of different Process Control Agents (i.e., methanol, hexane, and stearic acid) were investigated with powder morphologies, particle size distribution, and phase formation, and were sampled after up to 80 milling hours at 350 rpm. The powder morphologies and particle sizes were evaluated using scanning electron microscopy and laser diffraction analysis, respectively, and phases were identified via X-ray powder diffractometry. The results demonstrate for all conditions that, in the early stages, there was significant particle agglomeration due to the ductile-ductile feature of Fe and Nb powders, and latter an amorphization trend up to 80 milling hours. Methanol was the most efficient Process Control Agent in terms of avoiding cold welding, reducing of agglomeration, particle size distribution, reducing contamination and crystallinity reduction rate.

Structural, Thermal and Magnetic Analysis of Two Fe-X-B (X = Nb, NiZr) Nanocrystalline Alloy

“…Milling often facilitates the appearance of Fe-B compounds in alloys with Fe and B; however, in Nb-B milling, the Nb(B)-rich phase identified in this study was also reported in the literature [12][13][14][15][16][17][18]. The reaction between B and Nb is attributed to the negative mixing enthalpy which is about −39 kJ/mol.…”

“…It is evident the preparation conditions affect the final product and the mechanically alloyed powders' properties. The mechanical alloying technique is characterized by the repeated welding and fracturing of powder particles in a high-energy ball mill, which frequently results in excessive cold welding and ductile particle aggregation [14]. Even though agglomeration is a significant issue in the preparation process when the particulate size is reduced to the micron level, Hong and Kao [15] successfully incorporated very fine SiC particulates with a mean particle size of 0.3 mm into an Al matrix using the mechanical alloying (MA) process, which was used to improve the agglomeration of the reinforcement particulates as well as to reduce their crystalline size.…”