Limitations in the Grain Boundary Processing of the Recycled HDDR Nd-Fe-B System

Fully dense spark plasma sintered recycled and fresh HDDR Nd-Fe-B nanocrystalline bulk magnets were processed by surface grain boundary diffusion (GBD) treatment to further augment the coercivity and investigate the underlying diffusion mechanism. The fully dense SPS processed HDDR based magnets were placed in a crucible with varying the eutectic alloys Pr68Cu32 and Dy70Cu30 at 2–20 wt. % as direct diffusion source above the ternary transition temperature for GBD processing followed by secondary annealing. The changes in mass gain was analyzed and weighted against the magnetic properties. For the recycled magnet, the coercivity (HCi) values obtained after optimal GBDP yielded ~60% higher than the starting recycled HDDR powder and 17.5% higher than the SPS-ed processed magnets. The fresh MF-15P HDDR Nd-Fe-B based magnets gained 25–36% higher coercivities with Pr-Cu GBDP. The FEG-SEM investigation provided insight on the diffusion depth and EDXS analysis indicated the changes in matrix and intergranular phase composition within the diffusion zone. The mechanism of surface to grain boundary diffusion and the limitations to thorough grain boundary diffusion in the HDDR Nd-Fe-B based bulk magnets were detailed in this study.

Secondary Recrystallization Behavior in Fe-3%Si Grain-oriented Silicon Steel Produced by Twin-roll Casting and Simplified Secondary Annealing

Grain-oriented silicon steels were produced by the shortest processing route involving twin-roll strip casting, two-stage cold rolling with intermediate annealing, and simulated continuous annealing. The secondary recrystallization behavior of grain-oriented silicon steels under different inhibition conditions was in-situ observed by combining the confocal laser scanning microscopy (CLSM) and electron backscattered diffraction (EBSD) techniques. The results revealed that the optimal temperature of secondary recrystallization showed a proportional relationship with the Zenner pinning force. In the case of weak pinning force, the abnormal grain growth occurred quickly at ~1050 °C. The corresponding growth rates were in the range of 60–1400 μm/min and decreased gradually as the secondary recrystallization proceeded. In the case of strong pinning force, the incubation time and onset temperature of the secondary recrystallization was significantly increased, but the total time of the secondary recrystallization was obviously shortened from 685 s to 479 s, and the final magnetic induction of B8 was increased from 1.7 T to 1.85 T. After the secondary annealing, some island grains and coarse primary grains were retained. The formation of island grain was related to the low migration of grain boundaries. The findings of coarse γ- grains indicated that the primary grain size also played a crucial role during secondary recrystallization, apart from the primary recrystallized texture, which attracted more attention previously.

Investigation of Icrostructure, Mechanical and Temperature Effects on Biomedical Co-25Cr-9,5W-3,5Mo-1Si Alloys Fabricated by Additive Manufacturing

The Wolfram (W), Silicium (Si) and Molybdenum (Mo) doped Co-Cr biomedical alloy were fabricated by additive manufacturing method, which is part of powder metadology. The mixture of Wolfram (W), Silicium (Si), Chrome (Cr) and Cobalt (Co) alloy is known good wear and corrosion resistance among of biomedical applications. By addition of Molybdenum (Mo) into the structure of alloy, the structure become more stbale also increase the corrosion and wear resistance. In addition, the effects of secondary annealing process on the alloy were investigated. The microstructure of the produced alloy was analyzed by X-ray diffraction method XRD, Energy Dispersive X-Ray Analysis EDX and scanning electron microscope SEM. Moreover, Electrochemical corrosion test, micro hardness and density measurements were performed to investigate the mechanical properties of the alloy. As a result of the analyzes, the effects of Molydenum (Mo) doped and secondary annealing on the microstructure and mechanical properties of bioalloying were determined.

Effect of Primary Annealing Temperature on Primary and Secondary Recrystallization in Strip-Cast Grain-Oriented Silicon Steel

Grain-oriented silicon steel was produced by strip casting route. The effect of different annealing temperature on primary annealing and secondary annealing was investigated. The result showed that the average grain diameter increased and the grain uniformity was gradually destroyed with the increasing annealing temperature. Regardless of annealing temperature, the primary texture consisted of strong γ-fiber and weak λ-fiber. With the increase of annealing temperature, the γ-fiber intensity increased. In addition, the Goss component was not shown at 780-880 °C but appeared at 980 °C. After secondary annealing, complete abnormal grain growth occurred in all samples and the average grain diameter increased with the primary annealing temperature. The Goss sharpness of secondary grains firstly increased and then decreased with a peak value obtained at 830 °C. This result was explained in terms of the combination of the inhibiting force, primary grain diameter and primary texture.