The Stability of Al11Sm3 (Al4Sm) Phases in the Al-Sm Binary System

The relative stability of Al11Sm3 (Al4Sm) intermetallic phases was experimentally investigated through a series of heat treatments followed by microstructural, microchemical, and X-ray diffraction (XRD) analyses. The principal findings are that the high-temperature tetragonal phase is stable from 1655 to 1333 K and that the low-temperature orthorhombic phases, α and γ, have no range of full stability but are metastable with respect to the crystalline Al and Sm reference states down to 0 K. Thermodynamic modeling is used to describe the relative energetics of stable and metastable phases along with the associated two-phase mixtures. Issues regarding transition energetics and kinetics are discussed

Effects of hydrostatic pressure on the magnetic properties of disordered monosilicide FexCo1 - xSi alloys

Disordered FexCo1 - xSi alloys are known to be ferromagnetic in an iron concentration range starting at x = 0.2. We have measured their magnetization in magnetic fields up to 40 kOe at 4.2 K and under hydrostatic pressures up to 8 kbar, as well as their zero pressure susceptibility at 4.2 K in high magnetic fields of 150 kOe. We have also determined the Curie temperatures of the ferromagnetic samples under hydrostatic pressure up to 8 kbar from the temperature variation of the initial susceptibility. We determined a critical iron concentration of x ≃ 0.95 for ferromagnetism in FeSi rich alloys. From some of our results, the ferromagnetism in the CoSi rich alloys seems to appear in a rather homogeneous way, whereas the FeSi rich alloys in contrast exhibit local effects.Les alliages désordonnés FexCo1 - xSi sont ferromagnétiques pour une concentration en fer x supérieure à 0,2. Nous avons mesuré leur aimantation sous champ magnétique jusqu'à 40 kOe à 4,2 K et sous pression hydrostatique jusqu'à 8 kbar, de même que leur susceptibilité à la pression ordinaire sous champ magnétique de 150 kOe. Nous avons aussi déterminé les températures de Curie d'échantillons ferromagnétiques sous pression hydrostatique jusqu'à 8 kbar à partir de la variation thermique de la susceptibilité initiale. Nous avons déterminé une concentration critique x de l'ordre de 0,95 pour l'apparition du ferromagnétisme dans les alliages riches en FeSi. D'après nos résultats, le ferromagnétisme dans les alliages riches en CoSi semble apparaître de façon assez homogène, alors que les alliages riches en FeSi présentent au contraire des effets locaux