Magnetic properties of Ho2Fe17-xMnx - Influence of Mn substitution
The structural and magnetic properties of Ho2Fe17−xMnx (x=0−5) have been investigated by x-ray diffraction, Mossbauer spectroscopy and DC magnetization measurements (0-5 T) over the temperature range 4.5–350 K. Similar to other ferrimagnetic R2Fe17−xMnx systems, the unit cell volume generally increases with Mn content other than for low Mn values where a slight maximum is detected around x ~ 0.5. The nature of the magnetic phase transitions around TC is shown by Arrot plot analysis to be second order for all samples. The Curie temperature remains essentially unchanged for Mn contents up to x=1.0 (TC = 336 K for x=0.0, TC = 338 K for x=1.0) before decreasing steadily with further increase in Mn content (TC = 209 K for x=5). The 57Fe hyperfine interaction parameters have been determined from variable temperature Mossbauer spectra.
57 Fe Mössbauer spectroscopy of HoErFe 17-x Ga x C y compounds
${}^{57}\mathrm{Fe}$ M\"ossbauer studies were carried out on the phases ${\mathrm{HoErFe}}_{17\ensuremath{-}x}{\mathrm{Ga}}_{x}$ $(x=0\char21{}7)$ and ${\mathrm{HoErFe}}_{17\ensuremath{-}x}{\mathrm{Ga}}_{x}\mathrm{C}$ $(x=0,$ 1, and 2) at 25 K and room temperature. The weighted average hyperfine field at room temperature is found to increase initially for low Ga content and then decreases for phases with higher Ga concentration. The hyperfine fields at Fe sites follow the sequence $4f(6c)g6g(9d)g12j(18f)g12k(18h),$ which is determined mostly by the number of Fe and R nearest neighbors. The variation of the weighted average hyperfine field with temperature is found to obey ${T}^{2}$ behavior, suggesting the presence of single-particle excitations. Insertion of carbon at interstitial sites is found to increase the individual site hyperfine fields and hence an increase in the weighted average hyperfine field. The $12j$ and $12k$ sites of Fe show significant increase in isomer shift compared to other Fe sites.
Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment
Abstract The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M6C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M6C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M6C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M6C carbides, which results in a decrease of the lattice parameter.