Phases Τ2 Research Articles

Experimental study of the phase relations at 1023 and 1123 K in the Ag–Cu–Y system

The microstructure and phase constituents at 1023 and 1123 K of the annealed Ag–Cu–Y alloys were studied by using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). A new phase τ2 at 1023 K was found at ~33.3 at.% Y between Ag2Y and Cu2Y. Another ternary compound τ1(Ag3Cu12Y5) was confirmed to be stable at 1023 and 1123 K, and the liquidus temperatures of two annealed alloys with single phase τ1 were determined by thermal analysis techniques. Based on the obtained solubilities of compounds and phase equilibria data, the complete isothermal section at 1023 K and partial isothermal section with Y<50 at.% at 1123 K of the Ag–Cu–Y system were constructed.

Structure of the Al–Ge–Fe alloys in the liquid and solid state

X-ray diffraction study of liquid and solid Al–Ge–Fe alloys along the sections Al-Fe33.3Ge66.7, Fe-Al65Ge35 и Ge-Al78Fe22 has been discussed. It has been shown that addition of third component to the corresponding binary melt leads to the atomic clusters with structure similar to liquid germanium due to energy inequality of interactions in Al–Fe and Fe–Ge pairs and competition between Al and Ge atoms in formation of local structure around Fe atoms in the ternary melts. The Al88Ge8Fe4, Al68Ge21Fe11, Al64Ge18Fe18, Al55Ge30Fe15 melts have been quenched by melt spinning technique. The fully amorphous state was obtained only for the Al55Ge30Fe15 ribbon, the one with composition Al68Ge21Fe11 is amorphous-crystalline and Al88Ge8Fe4 и Al64Ge18Fe18 ribbons are microcrystalline. A new hexagonal τ1 phase (a=9.75(1)Å, c=8.80(1)Å) in the ingot Al55Ge30Fe15 and Al41Ge39Fe20 alloys and a new tetragonal phase τ2 (a=5.11(3)Å, c=4.60(2)Å) in the ingot Al20Ge53Fe27 alloy have been found. The annealed at 623K ribbons with composition Al88Ge8Fe4 and Al68Ge21Fe11 contain a new hexagonal phase τ3 (a=6.709(5)Å, c=9.07(1)Å), which is missing in the ingot.

The Phase Equilibria of the 75 at.% Al-Zn-Ce-Fe Quaternary System at 600 °C

The 600 °C isothermal section of the Al-Zn-Ce-Fe quaternary system with Al being fixed at 75 at.% has been studied experimentally by means of scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and x-ray powder diffraction. Four four-phase regions have been identified in this section, namely, τ2+Liq.+α-Al+FeAl3, τ2+Ψ+α-Al+FeAl3, τ2+Ψ+α-Al+αAl11Ce3, τ2+Ψ+αAl11Ce3+αAl3Ce. One Al-Ce-Fe ternary phase Ψ (CeFe2Al10) and another Al-Zn-Ce ternary phase τ2 (Al2Zn2Ce) has been found in this section but no quaternary compound has been found.

Experimental investigation and thermodynamic calculation of the Al–Si–Ti system in Al-rich corner

The phase equilibria in Al-rich corner of the ternary Al–Si–Ti system were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimeter (DSC). The ternary phase τ2 (Ti33Al15Si52, ZrSi2-type) existed stably and equilibrated with TiAl3, fcc(Al) and Si. The DSC results from room temperature to 1000°C indicated that the endothermic peaks corresponded to the quasi-peritectic reaction, liquid+TiAl3→τ2+fcc(Al), at 595°C and the eutectic reaction, liquid→τ2+fcc(Al)+Si, at 575°C. Based on the experimental results, a set of self-consistent thermodynamic description of the Al–Si–Ti system was obtained. The calculated isothermal section at 450, 500, 550 and 700°C and the invariant reactions agreed well with the experimental data.

Phase Equilibria of the Al-Zn-Fe-Ti Quaternary System at 600 °C

Isothermal sections of the Al-Zn-Fe-Ti quaternary system at 600 °C with Al being fixed at 75 and 50 at.%, respectively, have been determined experimentally by means of scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and x-ray powder diffraction. Two four-phase regions and nine four-phase regions have been identified in the 75 at.% Al and 50 at.% Al sections, respectively. Two Al-Fe-Ti ternary phases τ2 (Al2FeTi; D8a, Mn23Th6-type cubic), τ3 (Al8FeTi3; L12, AuCu3-type cubic) and one Zn-Fe-Ti ternary phase T have been found in 50 at.% Al section. The XRD analysis of Al50Zn25Ti25 indicates it is not a true ternary compound but the extension of TiZn3. The Ti2Al5 phase which exists at temperature above 1150 °C in Ti-Al binary system is also found in the two isothermal sections.

On the reaction scheme and liquidus surface in the ternary system Al–Si–Ti

Abstract The constitution of the ternary system Al–Si–Ti is reinvestigated over the entire composition range using X-ray diffraction, energy dispersive X-ray analysis, differential thermal analysis up to 1500 °C and metallography. The ternary phases τ1 and τ2 are confirmed and their crystal structures and solid state phase equilibria are corroborated. The compositions observed confirm previous literature. The phase τ1 (I41/amd, Zr3Al4Si5-type) melts incongruently at 953 °C &lt; T &lt; 1000 °C into L + τ2 + TiSi2. The phase τ2 (Cmcm, ZrSi2-type) melts incongruently at 1338 °C into L + TiSi + TiSi2. The liquidus surface is characterized by a eutectic trough, which descends monotonically from the pseudobinary maximum emax1 L = βTi + Ti5Si3 at 1540 ± 5 °C through a series of transition reactions and ends in the ternary eutectic L = τ1 + (Si) + (Al) at 573 °C.

The microstructure analysis of Al–Cu–Cr phases in Al65Cu20Cr15 quasicrystalline particles/Al base composites

The microstructures of Al65Cu20Cr15 as-cast and as-quenched master alloys and Al–Cu–Cr phases in Al65Cu20Cr15 particles/Al base composites after hot-pressing are investigated by transmission electron microscope and electron probe microanalyser. Two icosahedral quasicrystals SIQC and FIQC, two approximants to icosahedral quasicrystal IIA and FIA, one decagonal quasicrystal DQC, three approximants to decagonal quasicrystal DA1, DA2 and Θ, a new Al–Cu phase ξ that have a monoclinic structure with lattice parameter a=1.2 nm, b=0.9 nm, c=0.8 nm, β=130° and three τ type phases τ2, τ4 and τ7 were found. The composition–structure diagram in the Al–Cu–Cr system was drawn from phases above, in which there are two e/a-constant lines: one is the icosahedral quasicrystalline line with e/a=1.86; the other is the decagonal quasicrystalline line with e/a=2.09.

Experimental study of ternary Pd-Zn-Se phase equilibria and Pd/ZnSe bulk diffusion

The ternary system Pd-Zn-Se was investigated at 340 °C. A complete isothermal phase diagram is given, containing the formerly known ternary phase Pd5ZnSe (τ1) as well as a newly discovered ternary phase τ2 of approximate composition Pd62Zn32Se6. The reaction diffusion between Pd and ZnSe was investigated at 340 °C with bulk diffusion couples Pd/ZnSe, annealed from 6 to 192 h, and the diffusion path is described. For the investigation x-ray powder diffraction, scanning electron microscopy, and energy dispersive x-ray analysis was used. Implications for the application of Pd as metallic contact to semiconducting ZnSe are outlined.