导　　师： 高汝伟;韩广兵

学科专业： 080501

授予学位： 博士

作　　者： ;

机构地区： 山东大学

摘　　要： 热处理的六元合金Nd12.8Fe72Co7.8B7Zr0.1Ga0.3铸片制备各向异性磁粉的可能性,并以三元合金Nd13.5Fe79.5B7为例研究了HDDR磁粉各向异性的起源和形成机理。主要研究工作如下： 1.理论研究工作 1/)从HDDR磁粉晶粒的特殊微结构出发,研究了HDDR NdFeB永磁合金的反磁化过程和矫顽力机理。结果表明：在lex确定的条件下,当2ro//lex＜1.67时/(r0和lex分别为晶粒表面结构缺陷厚度和晶粒间交换耦合长度/),决定矫顽力的主要机制是畴壁钉扎；当2ro//lex＞1.67时,决定矫顽力的主要机制是反磁化成核。当2ro//lex=1.67时,矫顽力出现最大值,并与相关的实验结果符合很好。 2/)研究了晶粒间界相对磁体矫顽力的影响,改进了晶粒边界的各向异性理论模型。假定晶粒间界相是具有相同厚度的非磁性薄层,且在晶粒间均匀分布,给出了晶粒边界两种不同的各向异性表达式K1'/(r/)和K1''/(r/)。结果表明：非磁性晶粒间界相是晶粒之间畴壁位移的钉扎部位。当晶粒间界相厚度d为零时,根据两种表达式计算的矫顽力Hc均相等。d取非零值时,根据两种表达式计算的Hc均随d的增加而上升。其中根据K1''/(r/)计算的Hc随d的增加而上升的速率快。可是较厚的晶粒间界相又将会导致磁体的磁化强度及剩磁下降很多,限制了磁体磁能积的提高。厚度约为1nm的晶粒间界相可综合提高磁体磁性能。合理地调节合金成分配方及工艺条件,确保磁体中包含少量的富Nd相,不包含α-Fe,可以得到高性能的HDDR NdFeB磁体。当d为1nm, r0约为畴壁厚度/(～4nm/)时,根据两种表达式计算的矫顽力都与相关的实验结果符合较好。 2.实验研究工作 1/)根据实验要求,对原有的实验设备进行了更新、升级和改造。调整并稳定了SC工艺的轮辊转速和石英喷嘴的压力,改造了扩散炉,增加了进气孔,配置了气体压力控制系统。 2/)采用 The NdFeB permanent magnetic materials with the greatest properties and developmental future can be divided into the sintered and bonded NdFeB magnets, according to their different preparation processes. Compared with the sintered magnets, the preparation technology of bonded magnets is simple and has low cost, high toughness and performance of resisting the damage and crack. Thus, the bonded magnets can be prepared into products with different shapes. The anisotropic magnetic powders used for producing the bonded magnets are usually prepared by the HDDR/(Hydrogenation, Decomposition, Desorption, Recombination/)process. By using this process, the original large Nd2Fe14B grains in the cast ingots are transformed into fine grains with diameter of around 0.3μm, which is close to single domain size of Nd2Fe14B phase. The special grain microstructure of HDDR magnets is different from that of both sintered magnets and nanocomposite magnets. Due to the coercivity of magnets closely related to the grain microstructure, so, the coercivity mechanism of HDDR bonded magnets is different from not only that of sintered magnets, but also that of nanocomposite magnets. So far, the coercivity mechanism of HDDR bonded magnets has not been completely clear yet. The HDDR magnetic powders are commonly prepared from the segregated master ingots, and their magnetic properties are low due to the existence of soft magnetic phaseα-Fe in the master ingots. The alloy flakes prepared by the SC /(strip casting/) process have a good columnar crystalline structure, the main phase Nd2Fe14B is uniformly separated by the symmetrical Nd-rich phase fine lamella and a-Fe is nonexistent, which is very suitable for preparing the HDDR magnetic powders. Morimoto et al. reported that the HDDR magnetic powders prepared directly from the SC alloy flakes without any heat treatment are isotropic. Subsequently, they prepared the anisotropic magnetic powers by homogenizing SC alloy flakes before the HDDR process. Up to date, the preparation of anisotropi

关 键 词： 工艺 磁粉 微结构 各向异性 矫顽力

领　　域： [冶金工程] [冶金工程]