Abstract
The Gd5(SixGe_1-x)₄ series alloys are promising candidates for the magnetic refrigeration. The effect of solidification rate on the phase composition and microstructure of the arc-melted Gd₅Si₂Ge₂ alloy was investigated in this paper. Three samples with different weight of 10 g, 40 g and 65 g but the same stoichiometric Gd₅Si₂Ge₂ composition were prepared by arc-melting using commercial Gd (99.9 wt.%). The X-ray diffraction (XRD) analysis showed that the medium weight sample (cca. 40 g) consists of single Gd₅Si₂Ge₂ phase, while the other two samples consist at least of two phases, i.e, Gd₅Si₄ and Gd₅Si₂Ge₂ phases within our XRD resolution. The cell growth and regular lines within the cell grains are the two main features observed by Scanning-Electron Microscope (SEM) and Optical Microscope (OM) in the as-cast samples. The line features in the medium weight sample were much less developed than those in the other samples. These lines were not confirmed to be the Widmanstätten structure of Gd₅ (Si, Ge) ₃ rods. The melt-spun Gd₅Si₂Ge₂ alloy at different wheel speeds confirmed the influence of solidification rates on the phase composition. PACS: 75.50.Cc; 81.30.Fb

Key words
magnetic refrigerating materials, microstructure, Gd₅Si₂Ge₂ lloymagneticphase transformation

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