Structural studies of (Al1−xGex)65Cu10+yMn25−y (0≤x≤0.4, 0≤y≤10)
TL;DR: In this paper, the effect of Ge concentration on the occurrence, growth and morphology of the quasicrystalline phases in the alloy system (AlGe) CuMn was investigated.
About: This article is published in Materials Letters.The article was published on 2002-12-01. It has received 2 citations till now. The article focuses on the topics: Y alloy.
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TL;DR: In this article, Tsai et al. reported the results of field and temperature dependent magnetization measurements on (Al,Ge)65CuMn quasicrystalline samples with ∼22 and 24 at.
Abstract: We report the results of field and temperature dependent magnetization measurements on (Al,Ge)65CuMn quasicrystalline samples with ∼22 and 24 at. % Mn. The Ge content is also kept ∼25 at. %. The data for these samples are then compared with the data taken on samples with low Ge content (∼10 and 0 at. %). Al40Ge25Cu10Mn25, a composition very close to one of the alloys studied here, is reported [Tsai et al., Jpn. J. Appl. Phys., 27, L2252 (1988)] in literature as a ferromagnetic, icosahedral QC with large TC. The detailed magnetic studies described here prove that the magnetism observed in these quaternary alloys is highly disordered. The two important observations made in our studies are (i) observation of short-range ferromagnetism in samples with high Ge and high Mn content, up to very high fields (H=5 T) and (ii) oscillatory magnetization (or existence of multiple minima in the M-T curves) observed for the same samples for H⩾1 kOe.
3 citations
Journal Article•
TL;DR: In this article, Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge -Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to 25%Mn, and 0 to 10%Cu.
Abstract: Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge-Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to 25%Mn and 0 to 10%Cu. The highest Curie temperature is 533 K for Al52.5Ge22.5Mu25 and 467 K for Al40Cu10Ge25Mn25. The magnetization ( σ20) of the Al-Ge-Mn alloys in a field of 20 kOe at room temperature increases from 0.2 to 0.5 emu/g with increasing Ge and Mn contents and the coercivity (Hc) is in the range of 0.7 to 1.1 kOe. The replacement of Al by 10%Cu is found to bring about significant increases of σ20 and Hc to 3.9 emu/g and 1.8 kOe.
1 citations
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TL;DR: Addition of small amounts of Si and Ru to Al-Mn and Al-Cr alloys appears to enhance stability of the icosahedral phase.
Abstract: We have used x-ray and electron diffraction to study the icosahedral phase in rapidly quenched alloys of Al with Mn, Re, Cr, Ru, V, Mo, and W. We also find negative results in searches for the icosahedral phase in various other transition-metal alloys. Addition of small amounts of Si and Ru to Al-Mn and Al-Cr alloys appears to enhance stability of the icosahedral phase. We discuss the role of atomic packing, electronegativity differences, and electronic band structure in stabilizing this phase.
188 citations
TL;DR: In this article, Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge -Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to 25%Mn, and 0 to 10%Cu.
Abstract: Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge-Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to 25%Mn and 0 to 10%Cu. The highest Curie temperature is 533 K for Al52.5Ge22.5Mu25 and 467 K for Al40Cu10Ge25Mn25. The magnetization ( σ20) of the Al-Ge-Mn alloys in a field of 20 kOe at room temperature increases from 0.2 to 0.5 emu/g with increasing Ge and Mn contents and the coercivity (Hc) is in the range of 0.7 to 1.1 kOe. The replacement of Al by 10%Cu is found to bring about significant increases of σ20 and Hc to 3.9 emu/g and 1.8 kOe.
62 citations
TL;DR: In this article, it is proposed that descriptions of the decagonal phase by analogy to an icosahedral axial system be abandoned and that a different six-axis system be adopted instead.
Abstract: From a quenched, melt-spun ribbon of a specimen of Al76Mn24, bulk composition, the decagonal phase and a closely related ‘Al3Mn’ phase have been examined using analytical electron microscopic techniques. It is proposed that descriptions of the decagonal phase by analogy to an icosahedral axial system be abandoned and that a different six-axis system be adopted instead, and that the non-crystallographic space group previously proposed for the decagonal phase be changed to one containing glide planes. The ‘Al3Mn’ phase is seen to be an extremely close relative of the Al-Mn decagonal phase. However, the state of knowledge about the ‘Al3Mn’ structure is too poor to be of any use in improving the understanding of atomic arrangements in the Al-Mn decagonal phase.
62 citations
57 citations
TL;DR: In this paper, a decagonal approximant with diffraction features that are virtually indistinguishable from the true decagonal phase was discovered, and the pseudo-tenfold diffraction pattern from this phase contains low intensity, periodic diffraction spots corresponding to a d-spacing of ≈ 10 nm.
Abstract: As-cast samples of Al65Co20Cu15 made without Si were annealed for different times at 1200K. The decagonal phase was never observed. Instead, a decagonal approximant with diffraction features that are virtually indistinguishable from the true decagonal phase was discovered. The pseudo-ten-fold diffraction pattern from this phase contains low intensity, periodic diffraction spots corresponding to a d-spacing of ≈ 10 nm. High resolution electron microscope images taken along the pseudo-ten-fold zone-axis show crystalline domains decorated with ten-fold symmetric clusters. Several variants of this approximant with different periodicities are observed following isothermal annealing. These presumably arise from different packings of the ten-fold symmetric clusters. A new, crystal approximant phase also forms with annealing. Unlike previous reports, we find that silicon not only enhances decagonal formation but is necessary. For Si concentrations < ≈ 3·0 at.%, the weak diffraction spots are triangularly...
42 citations