Effects of high temperature annealing on the chemical homogeneity and Magnetostriction of Tb0.3Dy0.7Fe1.90 Intermetallic Compound

A rare earth-iron intermetallic compound Tb_0.3Dy_0.7Fe_1.90, also called Terfenol-D, has a gigantic room temperature magnetostriction at a relatively small magnetic field. In this study microsegregation of Tb and Dy in directionally solidified Terfenol-D was investigated. It was predicted from a calculated phase diagram and experimentally verified that Tb concentration at the center of the cell which solidified earlier was lower than that at the cell boundary. In order to homogenize this microsegregation, specimens were annealed at 1000°C for 40 hours, and various magnetic properties were measured as a function of applied field under uniaxial compressive stress in the range from 0.5 to 1.2 MPa. After the annealing, the maximum magnetostriction increased at a compressive stress below 9 MPa, magnetostrictive coefficient d₃₃ and magneto-elastic coupling coefficient k₃₃ increased, but permeability decreased. These results may be due to the reduction of magnetocrystalline energy which was locally very high before annealing due to microsegregation.     

亚里士多德论"动作"

介绍亚里士多德<诗学>中对"动作"概念的阐述."动作"是悲剧区别于其他艺术形式的重要方面.它从属于形象,与"行动"没有直接关系,但与情节有较大的相应性与限制性."动作"有助于思想表达的效果,"动作"不能过火.