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采用差热分析法研究了Nd_9Fe_(70)Ti_4C_2B_(15)永磁合金形核过冷度与其熔体过热度的关系。在此基础上,通过对不同熔体过热度的快淬薄带进行凝固组织结构分析、磁性能测试和差热分析,研究了熔体过热度对合金的非晶形成能力和晶化行为的影响。结果表明:在28~168 K的过热度范围内,Nd_9Fe_(70)Ti_4C_2B_(15)合金的过冷度随着熔体过热度的提高而显著增大了约80 K,它们之间呈现非线性关系;过冷度拐点对应的临界过热度为68 K,在小于68 K的过热度范围内,过冷度随过热度的提高而急剧增大了67 K,而在大于68 K的过热度范围内,过冷度随之而变化的幅度不大,其间的平均过冷度达到了174 K。熔体过热度为60 K时,快淬薄带的微观组织由Nd_2Fe_(14)B,Fe_3B和α-Fe纳米晶构成,其磁性能为H_(ci)=992.91 k A·m~(-1),B_r=0.56 T,(BH)_(max)=45.81 k J·m~(-3);熔体过热度提高至90和110 K时,快淬薄带的微观组织由纳米晶和非晶构成,且熔体过热温度越高,非晶的量越大;熔体过热度提高至150 K时,快淬薄带的微观组织由完全非晶构成。快淬薄带中的部分非晶或完全非晶在晶化退火过程中的相变都沿循以下路径:Am(非晶相)→Am’+Fe_3B→Fe_3B+Nd_2Fe_(23)B_3→Fe_3B+Nd_2Fe_(14)B+α-Fe。
The relationship between the undercooling of the nuclei and the degree of superheat of the Nd_9Fe_ (70) Ti_4C_2B_ (15) permanent magnetic alloy was studied by the differential thermal analysis. On the basis of this, the influence of melt superheat on the amorphous formability and crystallization behavior of the alloy was studied by analyzing the solidified microstructure of the quenched ribbon with different melt superheat degree, magnetic property test and differential thermal analysis . The results show that the supercooling degree of Nd_9Fe_ (70) Ti_4C_2B_ (15) alloy increases significantly by about 80 K with the increase of the degree of superheat of the melt in the superheat range of 28 ~ 168 K, showing a nonlinear The critical superheat corresponding to the inflection point of the subcooling is 68 K. In the superheat range of less than 68 K, the subcooling increases sharply by 67 K with the increase of superheating, while in the superheat range of more than 68 K, Within the degree of subcooling with the change is not large, during which the average undercooling reached 174 K. The microstructure of the quenched ribbon consists of Nd 2 Fe 14 B, Fe 3 B and α-Fe nanocrystals with a superconductivity of 60 K and a H ci of 992.91 kA · m -1 ), B_r = 0.56 T, (BH) _ (max) = 45.81 kJ · m -3. The microstructure of the quenched ribbon was improved by nanocrystalline and non-ferromagnetic Crystal, and the higher the melt overheating temperature, the greater the amount of amorphous; melt superheat to 150 K, the microstructure of the quenched ribbon consists of completely amorphous. The phase transitions during the crystallization annealing of partially amorphous or completely amorphous ribbon in the quenched ribbon all follow the following paths: Am (amorphous phase) → Am ’+ Fe_3B → Fe_3B + Nd_2Fe_ (23) B_3 → Fe_3B + Nd 2 Fe 14 B + α -Fe.