AN APPROACH TO DIRECTLY FABRICATE MAGNETIC REFRIGERANTS FROM CAST LA-FE-SI ALLOYS

摘要

A powder metallurgical approach based on the ability of some rare-earth compounds to react with hydrogen is presented as a way to obtain magnetocaloric components directly from as cast alloys. This work is based on La-based alloys with composition around LaFen.aSiu, obtained by induction melting and conventional casting processes. Due to the high content of α-Fe and LaFeSi phase together with α-Fe and La(Fe,Si)_(13) main phase, such as-cast alloys were easily decrepitated via reaction with hydrogen at temperatures around 423 K. After such reaction the ingot pieces were, subsequently, easily milled into fine powder, pressed in the desired shape and sintered in high temperature. During the sintering process besides the desired partial consolidation of the parts, a microstructural and phase homogenization was observed, resulting in bodies with a 1:13 phase content as high as 98 wt%. A further process of adding desirable interstitial atoms, such as H, is possible due to the residual porosity inherent to the powder metallurgy process.