Microstructure Regulation of As-cast Nd-Fe-B Alloy by MS-G Technology
In this study,the as-cast Nd-Fe-B alloy was treated by the melt-spun and grain growth(MS-G)tech-nology,and the effects of copper roll speed and high temperature treatment on the microstructure of Nd-Fe-B melt-spun strip were investigated.The melt-spun strip shows uniform grain structure with grain size of 0.1 μm at roll speed of 25 m·s-1 and the XRD pattern shows diffraction peaks of Nd2Fe14B phase.The Nd2Fe14B grains in 25 m·s-1 melt-spun strip grow uniformly to 0.6 μm when treated at 880 ℃ for 2.0 h,and then further grow to 1.04 μm after the second heat treatment at 750 ℃ for 2.0 h.The increase of temperature will reduce the critical driving force △gc for abnormal growth of Nd2Fe14B grains,as a result,shorten the incubation period and result in the earlier appearance of abnormal grains.The two-step heat treatment prolongs the incubation period of ab-normal grain growth by cooling treatment,thereby,promoting the Nd2Fe14B grains to grow uniformly at a lower temperature.
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