The effectsof melt overheating degree on the undercooling degree and resultant solidification structures of Nd9Fe85-xTi4C2Bx（x=10, 12） glass-forming alloyswerestudied by differential thermal analysis combining with solidification structure analysis. The results indicate that the undercooling degree of Nd9Fe85-xTi4C2Bx（x=10, 12） alloys significantly increaseswith the rise of melt overheating degree, and two overheating degree thresholds corresponding to the drastic increase of the mean undercooling degree are found for each of the alloys. The existence of two turning points of the mean undercooling degreescan be linked to the structure transitions inside the overheated melts, which result in the evident increase of volume fraction of amorphous phasein the solidified structures.
采用铜模吸铸制备了厚度为0.8 mm,成分为Nd9Fe81-x-yTi4C2BxNby(x=11,13,15;y=0,4)的Nd2Fe14B/Fe3B型纳米复合永磁合金块体样品,研究了添加Nb对合金铸态组织及其晶化行为的影响,并测试了其磁性能。结果表明:在合金中添加4%(原子分数)Nb元素,不仅能抑制吸铸样品表面Nd2Fe23B3软磁性相、Nd1.1Fe4B4非磁性相和未知相的形成,导致Nd2Fe14B,Fe3B和α-Fe相的相对量增加,而且促使样品内部在非晶基体上形成了少量的Nd2Fe14B和α-Fe,Fe3B纳米晶。添加了Nb的合金吸铸样品表现出一定的硬磁性,其中Nd9Fe66Ti4C2B15Nb4吸铸样品具有最高的矫顽力(Hci=116.66 k A·m-1);添加4%(原子分数)Nb使得合金在晶化过程中由原来的异相同温一步晶化转变为两步晶化,且初始晶化温度Tx均明显降低,两个放热峰的ΔTpx均增大。
采用差热分析（DTA）和X 射线衍射分析（XRD）相结合的方法对纳米复合永磁合金Nd9Fe85-xTi4C2Bx （x=10~15）铸锭进行研究,确定了合金的液相线温度、固相线温度以及其它相变的温度区间,推断了合金凝固过程中发生的相变.结果表明,随着合金铸锭中B含量从10%（原子分数）增加至15%（原子分数）,合金的液相线温度从1498.5 K 逐步降低至1472.5K,而固相线温度从1353.5 K 逐步升高至1358.3K.可以推断合金铸锭的凝固相变如下：在它们的液相线下的第-个相变温度区间,L→γGFe,L＋γGFe→Nd2Fe14B;在第二个相变温度区间,L→γGFe,L→Nd2Fe14B＋Fe3B;在第三个相变温度区间,L→Nd2GFe14B,L→Nd2Fe14B＋Fe3B ＋ Nd1.1Fe4B4.
