Bulk metallic glass (BMG) formers are multicomponent alloys that vitrify with remarkable ease during solidification. Technological interest in these materials has been generated by their unique properties, which often surpass those of conventional structural materials. The metastable nature of BMGs, however, has imposed a barrier to broad commercial adoption, particularly where the processing requirements of these alloys conflict with conventional metal processing methods. Research on the crystallization of BMG formers has uncovered novel thermoplastic forming (TPF)-based processing opportunities. Unique among metal processing methods, TPF utilizes the dramatic softening exhibited by a BMG as it approaches its glass-transition temperature and decouples the rapid cooling required to form a glass from the forming step. This article reviews crystallization processes in BMG former and summarizes and compares TPF-based processing methods. Finally, an assessment of scientific and technological advancements required for broader commercial utilization of BMGs will be made.

Processing of Bulk Metallic Glass

A novel porous glass-ceramic with a skeleton of a NASICON-type copper(II) titanium phosphate was prepared via the controlled crystallization of a glass and the subsequent chemical leaching of the resulting dense glass-ceramic. A volume-crystallized dense glass-ceramic comprised of CuTi2(PO4)3 and Cu3(PO4)2, whose surface was covered by a thin layer of CuO, was prepared by reheating a glass with a nominal composition of 50CuO20TiO230P2O5 (in mol%) in air. When the resulting glass-ceramic was leached with dilute HCl, the Cu3(PO4)2 and CuO phases were dissolved out selectively, and a cuprous NASICON crystal of CuTi2(PO4)3 was converted to its cupric type, CuTi4(PO4)6, which was left as a skeleton of the porous materials. The specific surface area and the average pore radius of the porous glass-ceramic obtained were ∼70 m2/g and ∼7 nm, respectively. The porous glass-ceramic showed high catalytic activities for the dehydration of 2-propanol.

Microporous Glass‐Ceramics in NASICON‐Type Copper(II) Titanium Phosphate

New phosphates with the general formula M0.5(1 + x
 )Fe
 x
 Ti2 − x
 (PO4)3 (M = Co, Ni, Cu; 0 ≤ x ≤ 2) have been synthesized by a sol-gel process. We have studied phase relations in these systems and determined the composition stability limits of NASICON-type solid solutions. The catalytic properties of the phosphates for methanol dehydration and dehydrogenation reactions have been investigated in an inert atmosphere.

Synthesis and catalytic properties of M0.5(1 + x)FexTi2 − x(PO4)3 (M = Co, Ni, Cu; 0 ≤ x ≤ 2) for methanol conversion reactions

Complex phosphates Ca0.5 + x
 Zn
 x
 E2 − x
 (PO4)3 (E = Ti, Zr) having NaZr2(PO4)3 (NZP) structure have been prepared and characterized by X-ray diffraction, electron probe microanalysis, IR spectroscopy, and differential thermal analysis (DTA). Their phase formation has been studied by X-ray powder diffraction and DTA. The concentration and temperature fields of existence of these NZP phases have been determined: substitution solid solutions exist in the range of compositions where 0 ≤ x ≤ 0.5. The Ca0.7Zn0.2Ti1.8(PO4)3 crystal structure has been refined by the Rietveld method (space group $$R\bar 3$$
 , a = 8.3636(4) A, c = 21.9831(8) A, V = 1331.7(1) A3, Z = 6). The framework in the NZP structure is built of octahedra, which are populated by titanium and zinc atoms, and PO4 tetrahedra. Calcium atoms occupy extraframework positions. Extensive solid solution formation due to the accommodation of cations(2+) in the interstices within the NZP framework (M) and in the framework-forming octahedra (M′) makes it possible to design a plurality of new M0.5 + x
 M′
 x
 E2 − x
 (PO4)3 phosphates with tailored structures.

Phosphates having the NaZr2(PO4)3 structure and containing titanium (or zirconium) and elements in oxidation degree 2+ (calcium or zinc)

Phosphates M05Ti2(PO4)3 (M = Ni, Zn) were synthesized by the sol-gel method and characterized by the methods of X-ray diffraction, IR spectroscopy, and electronic microprobe analysis Structures of Ni05Ti2(PO4)3 and Zn05Ti2(PO4)3 were studied by Rietveld method using the X-ray powder diffraction data

Synthesis and structure of phosphates M 0.5 Ti 2 (PO 4 ) 3

The Structure of the High Temperature Forms of Cu0.5Ti2(PO4)3 and D0.5Cu0.5Zr2(PO4)3

The layer growth of the A15 (Nb3Sn) superconducting phase produced by the internal tin method on model monofilament wires was studied by neutron diffraction and electron microscopy techniques. Different ratios of the inner part of the wire (Sn/Cu) and the effect of the addition of 1% of zirconium to niobium were studied. The high temperature heat treatment plays a key role on the A15 formation and on the cost of the final wires produced. Different temperatures in the range 650-725°C and different annealing times in the range 8-200 hrs have led to the preparation of 72 different samples. The neutron diffraction study has evidenced the different phases formed during the heating treatment and the electron microscopy study has evidenced a power law for the growth rate of the A15 phase. In both studies the addition of zirconium in niobium is very effective on the growth rate of the A15 phase.

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Neutron diffraction studies of the Zr/Nb effects on the Nb3Sn phase formation of monofilament wires

Crystallization Behaviour of Zr65-x-yTixAlyHf5Cu20Ni10Bulk Metallic Alloys By Insitu Neutron Diffraction

Physintercalation of Alkanes in CsC24: Influence of the Molecular Size on the Structural Modifications

During the crystallization study of the bulk metallic glass 46.8Ti8.2Cu7.5Ni10Be27.5 (Vit4) we have demonstrated that the primary crystals appearing during isothermal annealing in the glass region, above Tg and before Tx, were of quasicrystalline nature and beryllium free. The formula of the quasicrystalline phase so obtained and determined by electron techniques (EDX and EELS) was Zr63Ti14.4Ni12.4Cu10.2. We have synthesized phases in the system Zr75-xTixCu25-yNiy by melt spinning and obtained either amorphous or quasicrystalline phases. For the amorphous phases, we have studied the crystallization by in-situ neutron diffraction and obtained quasicrystals as primary crystals. Neutron and X-ray diffraction, DSC studies are presented.

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Jean Louis Soubeyroux

Papers

The Structure of the High Temperature Forms of Cu0.5Ti2(PO4)3 and D0.5Cu0.5Zr2(PO4)3

Neutron diffraction studies of the Zr/Nb effects on the Nb3Sn phase formation of monofilament wires

Crystallization Behaviour of Zr65-x-yTixAlyHf5Cu20Ni10Bulk Metallic Alloys By Insitu Neutron Diffraction

Physintercalation of Alkanes in CsC24: Influence of the Molecular Size on the Structural Modifications

Quasicrystal Formation in the System Zr75-xTixCu25-yNiy