中文摘要：

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。

英文摘要：

The dependence of the nucleation undercooling degree of Nd_9Fe_（70）Ti_4C_2B_（15） permanent magnetic alloy on its melt overheating degree was studied by differential thermal analysis. On this basis,the effects of melt overheating degree on the glass formability and crystallization behavior of the alloy was investigated by the solidification structure analysis,magnetic properties test and differential thermal analysis of the ribbons melt-spun at different melt overheating degree. It was shown that when the overheating degree was in the range of 28 - 168 K,the undercooling degree of the Nd_9Fe_（70）Ti_4C_2B_（15） alloy significantly increased by 80 K with the raise of the melt overheating degree,and a nonlinear relation between them was presented; the melt overheating degree threshold corresponding to the turning points of the mean undercooling degree was found to be 68 K. The microstructure of the ribbon quenched at melt overheating degree of 60 K was consisted of Nd_2Fe_（14） B,Fe_3B and α-Fe nanocrysallines,with the magnetic properties of H_（ci）= 992. 91 k A·m~（-1）,B_r= 0. 56 T,（ BH）_（max）= 45. 81 k J·m~（-3）; the microstructure of the ribbon quenched at melt overheating degree of 90 and 110 K were consisted of nanocrysallines and amorphous,and the higher the overheating degree,the larger the amount of the amorphous; the microstructure of the ribbon quenched at melt overheating degree of 150 K was consisted of complete amorphous. The phase transformation of the partial or complete amorphous in the ribbons during crystallizing annealing may take place in the following sequences： Am（ amorphous phase） →Am＇ ＋ Fe_3B→Fe_3B ＋ Nd_2Fe_（23）B_3→Fe_3B ＋ Nd_2Fe_（14） B ＋ α-Fe.