Enhancement of coercivity of hot-deformed Nd–Fe–B anisotropic magnet by low-temperature grain boundary diffusion of Nd60Dy20Cu20 eutectic alloy

2013 ◽  
Vol 69 (9) ◽  
pp. 647-650 ◽  
Author(s):  
H. Sepehri-Amin ◽  
J. Liu ◽  
T. Ohkubo ◽  
K. Hioki ◽  
A. Hattori ◽  
...  
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Eutectic Alloy ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Anisotropic Magnet

Diffusion Mechanisms in Nanocrystalline and Nanolaminated Au-Cu

2007 ◽  
Vol 266 ◽  
pp. 13-28 ◽  
Author(s):  
Alan F. Jankowski
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Diffusion ◽  
Bulk Diffusion ◽  
Grain Boundary Diffusion ◽  
Dominant Mechanism ◽  
Temperature Range ◽  
Diffusion Mechanisms ◽  
Kinetics Of

Thermal anneal treatments are used to identify the temperature range of the two dominant diffusion mechanisms – bulk and grain boundary. To assess the transition between mechanisms, the low temperature range for bulk diffusion is established utilizing the decay of static concentration waves in composition-modulated nanolaminates. These multilayered structures are synthesized using vapor deposition methods as thermal evaporation and magnetron sputtering. However, at low temperature the kinetics of grain-boundary diffusion are much faster than bulk diffusion. The synthesis of Au-Cu alloys (0-20 wt.% Cu) with grain sizes as small as 5 nm is accomplished using pulsed electro-deposition. Since the nanocrystalline grain structure is thermally unstable, these structures are ideal for measuring the kinetics of grain boundary diffusion as measured by coarsening of grain size with low temperature anneal treatments. A transition in the dominant mechanism for grain growth from grain boundary to bulk diffusion is found with an increase in temperature. The activation energy for bulk diffusion is found to be 1.8 eV·atom-1 whereas that for grain growth at low temperatures is only 0.2 eV·atom-1. The temperature for transitioning from the dominant mechanism of grain boundary to bulk diffusion is found to be 57% of the alloy melt temperature and is dependent on composition.

Low-Temperature Grain Boundary Diffusion Data Measured from Historical Artifacts

2004 ◽  
Vol 852 ◽  
Author(s):  
R.J. Kremer ◽  
M.A. Dayananda ◽  
A.H. King
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Room Temperature ◽  
Boundary Diffusion ◽  
Diffusion Processes ◽  
Grain Boundary Diffusion ◽  
Accelerated Tests ◽  
Temperature Diffusion ◽  
Diffusion Profiles

ABSTRACTDiffusion processes in typical metals are slow at room temperature but there are many applications for which very long-term use is envisaged and stability needs to be assured over a timescale of 10, 000 years, where even slow processes can be important. It is common to perform accelerated tests at higher temperatures and extrapolate the necessary information from the measurements so obtained. We have tested the validity of this type of extrapolation for room-temperature, grain boundary diffusion in the copper-silver system, by measuring low-temperature diffusion profiles in antique samples of Sheffield plate.

scholarly journals Low Temperature Grain Boundary Diffusion of Chromium in SUS316 and 316L Stainless Steels

2004 ◽  
Vol 45 (10) ◽  
pp. 2945-2950 ◽  
Author(s):  
Masaki Mizouchi ◽  
Yoshihiro Yamazaki ◽  
Yoshiaki Iijima ◽  
Koji Arioka
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Stainless Steels ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion

Microstructural Evaluation of Dy-Ni-Al Grain-Boundary-Diffusion (GBD) Treatment on Sintered Nd-Fe-B Magnet

2010 ◽  
Vol 654-656 ◽  
pp. 2919-2922 ◽  
Author(s):  
Naoko Oono ◽  
Masato Sagawa ◽  
Ryuta Kasada ◽  
Hideki Matsui ◽  
Akihiko Kimura
Keyword(s):  
Melting Point ◽  
Grain Boundary ◽  
Eutectic Alloy ◽  
Alloy Powder ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Rich Phase ◽  
X Ray ◽  
Microstructural Evaluation

A novel GBD treatment with Dy-Ni-Al eutectic alloy powder enhanced the coercivity of the sintered Nd-Fe-B magnet plate as thick as 5mm to 1760 kA/m (22 kOe) without reducing the remanence. The results of wavelength dispersive X-ray spectroscopy (WDS) indicated that this industrially epoch-making treatment spread Dy, which is a coercivity enhancing element, from the surface to the centre of the magnet through Nd-rich phase. Microstructural observations suggested that Ni and Al, which are the melting point depressants of Nd and Dy, enabled the high diffusivity of Dy.

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