Thermo-Mechanical Processing of Hard-Ferromagnetic FePd-based Intermetallics

摘要

Here, combinations of XRD, SEM, TEM and VSM have been used to study processing-microstructure-property relationships in CR-processed equiatomic FePd intermetallics. Some of the main conclusions may be summarized as follows: 1) The coercivity increases (magnetic hardening) during CR processing due to the increase in the volume fraction of L1_0-ordered material. 2) The decrease in coercivity or magnetic softening during overaging has been attributed largely to grain growth in the fraction of CR transformed grains. 3) The maximum value of coercivity achieved during CR processing depends on the grain size of the CR transformed grains and the defect content retained by the latter. 4) The stored strain energy of cold-work provides an additional driving force for the microstructural transformation and thus accelerates the transformation kinetics. 5) CR processing enables fabrication of bulk FePd intermetallics with nano-scale microstructures that exhibit considerably enhanced coercivity (up to ≈1.4 kOe) and appears suitable for application to a broad range of intermetallics. 6) A nucleation and growth process with nucleation-limited kinetics akin to a 'massive' ordering transformation is responsible for the formation of the microstructures that provide the maximum coercivity.