La(Fe_(0.94)Co_(0.06))_(11.8)Si_(1.2)循环磁化过程中微观结构的演变

The transformation of microstructure for La(Fe_(0.94)Co_(0.06))_(11.8)Si_(1.2) during magnetic field cycling

电弧熔炼制备的铸态La(Fe0.94Co0.06)11.8Si1.2合金在1 373 K(120 h)热处理之后冰水快淬得到了NaZn13相金属间化合物.将材料应用于自制磁热循环装置中,在其居里点Tc附近进行磁化-去磁化循环处理.经过绝热循环磁化5千次后,通过扫描隧道显微镜观察到化合物La(Fe0.94Co0.06)11.8Si1.2的磁畴细化;通过HRTEM观察到化合物晶粒内部出现了应变区,在[001]方向聚集了大量的位错线.循环磁化8千次后,晶粒内部出现了亚晶界、微观裂缝结构等不可逆结构演变.磁畴结构与微观结构的演变是相互联系、相互影响的,经过不断的循环磁化去磁化处理,材料将会出现磁热性能和结构的同时衰变.

NaZnl3 phase intermetallic compounds came into being after the as-cast La（ Fe0.94 Co0.06 ）ll.s Sil.2 alloys were prepared by electric arc melting, and annealed at 1 373 K for 120 hours then quenched with ice water. Near their Curie point Tc, these materials were applied to magnetic thermal cycling device for cyclic magnetization. The magnetic domain of La（ Fe0.94Co0.06 ） 11.8Si1.2 compounds became refinement after thermal isolation magnetization cycled 5 000 times, as observed by scanning tunneling microscopy （ STM ） ; there are many strain zones occurred inside the grain of material and a large number of dislocation lines gathered in [001 ] direction observed by HRTEM. There are many irreversible structural transformations, such as subboundary and micro crack structure inside the grain of material by 8 000 times cycling. The evolution of the magnetic domain structure and the microstructure were interrelated and influencing each other. Magnetocaloric properties and structure of the material will be decayed at the same time with continuous cyclic magnetization.