Structure and anelasticity of Fe3Ge alloy

Structure and Anelasticity of Fe-Ge Alloys

“…11 the temperature dependence of magnetization shows a shoulder around 525 K due to the Curie temperature of the β phase (T C = 530 K), present in this alloy although not resolved by XRD, but also indicated by DSC. Another shoulder around 670 K is associated with the Curie temperature of the hexagonal ε phase T C = 638 K), which is dominating in the structure of the studied alloy, in agreement with DSC [7]. Finally, the magnetization approaches zero near 780 K corresponding to the Curie temperature of the cubic ε′ (L1 2 ) ordered phase (T C ≈ 750 K [11,12]).…”

“…The two-phase structure (ε + β) after casting can be observed by LM as dendrides of the ε phase grow into the (ε + β) matrix. These structures disappear after homogenizing for 24 h at 1273 K, and the two-phase structure (ε + β) reappears after additional low temperature annealing (100 h at 624 K), as also checked by EDX [7]. X-ray diffraction essentially corroborates these structures.…”

“…The hexagonal Fe 3 Ge type alloy. The results of observations and measurements by DSC, optical microscopy, EDX, and XRD on Fe -27 Ge have already been shown in [7] and will be summarized here only briefly, for comparison with the set of Fe -Ge alloys described before. Contrary to those bcc or bcc-originated alloys, the Fe 3 Ge -type alloy is basically of hexagonal structure.…”

“…The X-ray diagrams of samples annealed at 1273 K for 24 h and after a second heat treatment at 648 K for 100 h (Fig. 10) show mainly lines of the ε-phase and not of the β phase in the first case (probably because the amount of β phase or its particles are too small), while some ε′ phase cannot be excluded [7]. After the second anneal (100 h, 648 K), besides ε distinct lines of the hexagonal β phase (B8 1 ) and weak signs for a small amount of ε′ are detected.…”

“…Elastic and anelastic properties are deduced from the resonance frequency f (Young's modulus E ~ f 2 ) of flexural vibrations with the specimen clamped at one end measured during heating and cooling cycles between 300 and 850 K. The comparison of specimens tested after the homogenising treatment at 1273 K (24 h) and slow cooling, with those after an additional low temperature anneal (100 h at 648 K) shows two "critical points" in f (T) near ~ 373 K and ~ 633 K. The second one correlates with corresponding points in the curves of heat flow and magnetometry, the first one may be related to an effect in the thermo-magnetic curves if they are measured in a low magnetic field. Both of these effects can be considered as order-disorder transitions [7].…”