Details

Autor(en) / Beteiligte

• Lin, Yin-Chih
• Lin, Chien-Feng
• Yang, Jin-Bin
• Lee, Hwa-Teng

Titel

Microstructures and magnetostriction of two-phase Fe66-Pd30-Ni4 high-temperature ferromagnetic shape memory alloys

Ist Teil von

• Journal of applied physics, 2011-04, Vol.109 (7)

Erscheinungsjahr

2011

Quelle

AIP Journals Complete

Beschreibungen/Notizen

• The microstructures and magnetostrictive strains of ferromagnetic shape memory Fe-Pd30 alloy systems with additions of Ni elements (4 at.%) have been investigated by a magnetostriction meter, scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The research results show that the magnetostrictive strains of the Fe66-Pd30-Ni4 alloys after homogenization treatment (λ‖s=79×10-6) are higher than those of the as received materials (λ‖s=55×10-6). The lower magnetostriction of the as received metal is due to segregation-impeded parts of the L10 twin boundary motion in realistic magnetic fields. In addition, an important discovery in this study is that doping the Fe-Pd30 alloy system with Ni substitution for Fe seems to prevent the decomposition of L10 + L1m twin phase into stoichiometric L10 + L1m + αbct structures when the strain-forged alloys are solution treated and recrystallization annealed, and then aged at 400 °C for 100 hours. The magnetostrictive strains of the 400 °C/100 h aged sample are maintained with λ||s=62×10-6; λ⊥s=-11×10-6, and the XRD analysis revealed a complete absence of αbct phasein the aged sample. This magnetic property of the alloys is suitable for application in a high temperature and high frequency (T<400 °C) environment. The strain-forged samples were solution treated (ST) and recrystallization annealed, and then aged at 500∼700 °C for 100 hours. XRD analysis revealed the formation of an αbct phase when the specimen was aged at 500 °C for 100 hours. This αbct phase occurrence causes large reductions in the magnetostrictive strains. When the samples were aged at 600∼700 °C for 100 hours, overaging occurred, the martensitic stoichiometric L10 + L1m + αbct lamellar structures dissolved into the matrix simultaneously, and the magnetostrictive strains gradually recovered.