La对大块LaFe_(11.6)Si_(1.4)合金的相、组织的影响与优化合金的磁热性能研究  

Phase and Structure of Bulk LaFe_(11.6)Si_(1.4) Alloy and Studies of Magnetocaloric Effect of Optimization Alloy

作　　者：陈湘[1] 吕文梅 杨崧 李炎钊 陈云贵[2] Chen Xiang;Lv Wenmei;Yang Song;Li Yanzhao;Chen Yungui(College of Physics and Electronic Information Engineering,Neijiang Normal University,Neijiang 641100,China;School of Materials Science and Engineering,Sichuan University,Chengdu 610065,China)

机构地区：[1]内江师范学院物理与电子信息工程学院,四川内江641112 [2]四川大学材料科学与工程学院,四川成都610065

出　　处：《稀有金属》2024年第1期25-34,共10页Chinese Journal of Rare Metals

基　　金：四川省科技厅重点研发项目(22ZDYF3309)资助。

摘　　要：研究了添加正常化学计量情况下La质量的3%和9%作为熔损的千克级浇铸LaFe_(11.6)Si_(1.4)圆盘试样的相和组织结构。结果表明,在铸态时两个圆盘的主相均为Fe和LaFeSi相,且在添加9%的La浇铸圆盘各处试样中均能观察到La_(5)Si_(3)相;在两个圆盘的边缘能观察到1:13相的存在,但在1/2半径处、圆心处却不能观察到1∶13相。在1503 K热处理不同时间后,添加9%的La圆盘各处试样中Fe和LaFeSi相含量均低于添加3%的La圆盘对应试样。优化La添加量的合金圆盘(添加9%的La)热处理后,X射线衍射(XRD)图谱和扫描电子显微镜(SEM)图像证明Fe和LaFeSi相含量随热处理的时间延长而降低,观察不到在铸态试样中因冷却速率差异导致的组织偏析,且中心试样和边缘试样的相和组织结构基本相似。母合金中Fe,LaFeSi,La_(5)Si_(3)相可以在热处理过程中以某种扩散形成1:13相,但在经过10 h热处理后的优化合金中心试样中仍能观察到添加过量La而引起的La_(5)Si_(3)相。优化合金在经过5,8和10 h处理后中心试样的居里温度在191.5 K附近,在2 T磁场下对应的最大磁熵变和相对制冷能力分别为20.0,24.4,24.4 J·kg^(-1)·K^(-1)和158,183,188 J·kg^(-1),这些参数同对应的边缘试样基本相同。In this paper,the phases and microstructures of the kilogram-class LaFe_(11.6)Si_(1.4) as-cast discs with 3%and 9%excessive La element as melting loss were studied firstly.X-ray diffraction (XRD) patterns showed that the main phases in different regions of the two discs were Fe and LaFeSi,and La_5Si_(3) phase existed in the disc with 9%excessive La.In cast center sample,Fe was in a parallel columnar shape,while the white rich La phase was located between columnar dendrites,indicating that during the solidification process,nucleation occurred first due to the lowest solidification point of Fe.The maximum subcooling occurred along the vertical direction of the mold bottom,and Fe nuclei grew along this direction to form columnar crystals perpendicular to the mold bottom.Due to the difference in cooling speed between the lower and upper parts of the casting disc,the fast cooling zone in the lower part led to fine grain,while in the upper part,coarse grain was formed in the opposite direction.1∶13 phase could be observed in the edge region of two discs,however it could not be observed in the samples at 1/2 radius and center regions.In the edge and center regions of the four symmetrical fan-shaped bulks of 9%La annealed at 1503 K for 3,5,8 and 10 h,the contents of Fe and LaFeSi phases were smaller than those of the corresponding region samples in 3%La.The phases and structures of the center and the edge region samples in the annealed 9%La were basically similar.And more,the microsegregation caused by the difference of cooling rate in the as-cast disc could not be observed.La_5Si_(3) phase caused by excessive La could still be observed in the center region sample of 9%La annealed for 10 h.This indicated that once La_5Si_(3) phase was present in the cast LaFe_(13-x)Si_(x) alloy,it was difficult to eliminate it through later heat treatment.At the same time,energy spectrum analysis showed that the atomic percentages of La,Fe and Si in 1∶13 phase were 8.32%,80.14%and 11.55%,respectively.This was similar to Fe atomic per

关 键 词：千克级LaFe_(11.6)Si_(1.4)合金 合金组织 相关系 磁热性能 

分 类 号：TG132.2[一般工业技术—材料科学与工程]