Microstructural evolution,magnetocaloric effect,mechanical and thermal properties of hot-pressed LaFe_(11.6)Si_(1.4)/Ce_2Co_7 composites prepared using strip-cast master alloy flakes

摘要

LaFe_(11.6)Si_(1.4)/Ce_2Co_7 composites were prepared using strip casting flakes (SC-flakes) and heat treated flakes (HT-flakes) by hot pressing,denoted as SC-HP and HT-HP,respectively. Subsequently,additional heat treatment was performed. The microstructure evolution,phase constitution,magnetocaloric and mechanical properties of these SC-HP and HT-HP samples over a large range of heat treatment temperatures and times were compared. Heat treatment at 1373 K for 12 h resulted in Ce and Co diffusion into La(Fe,Si)_(13) particles. An increase of T_(peak) from 228 to 289 K and a large (-ΔS_M)~(max) increase from 1.89 to 5.01 J kg~(-1) K~(-1) (ΔH = 2 T) was observed in SC-HP samples. Combining hot pressing and heat treatment considerably reduces processing time. 90% of theoretical density,compressive strength greater than 450 MPa,large (-ΔS_m)~(max)of ～4.73-5.01 J kg~(-1 )K~(-1) and good thermal conductivity (λ) above 5.5 Wm~(-1)K~(-1) were also achieved,suggesting the practical use of such heat treated composites with attractive magnetocaloric,mechanical and thermal properties.