Bulk Glassy Alloys: Historical Development and Current Research

This paper reviews the development of current research in bulk glassy alloys by focusing on the trigger point for the synthesis of the first bulk glassy alloys by the conventional mold casting method. This review covers the background, discovery, characteristics, and applications of bulk glassy alloys, as well as recent topics regarding them. Applications of bulk glassy alloys have been expanding, particularly for Fe-based bulk glassy alloys, due to their unique properties, high glass-forming ability, and low cost. In the near future, the engineering importance of bulk glassy alloys is expected to increase steadily, and continuous interest in these novel metallic materials for basic science research is anticipated.

Effect of niobium on glass-formation ability and soft magnetic properties of Gd-doping glassy alloys

The effect of niobium on glass-formation ability and soft magnetic properties were studied in Fe-Gd-B glassy alloys. The glassy alloys exhibited high glass-formation ability when the element of Nb was added. Bulk glassy rod （Fe0.87Co0.13）68.5Gd3.5Nb3B25 with a diameter up to 3 mm was produced by copper mold casting. The size of the atom might play an important role in increasing glass-formation ability. The coercive force of glassy （Fe0.87Co0.13）71.5.xGd3.sNbxB25 （x=1.2, 1.5, 2, 2.5, 3, 4） alloys decreased after the addition of niobium element and was in the range of 1.5-2.9 A/m. The permeability spectrum of （Fe0.87Co0.13）70.3Gd3.5Nb1.5B25 glassy ribbon showed that the relaxation frequency （f0） was 6.1 MHz.

Work Functions of Pd_(83.5)Si_(16.5)and Cu_(70)Ti_(30)Glassy Alloys

The work functions before and after crystallization of two glassy alloys,Pd_(83.5)Si_(16.5) and Cu_(70)Ti_(30) have been measured by means of the con- tact potential difference method in the secondary electron field at room temperature under 10^(-5) Pa vacuum.The results show that the work functions of both glassy alloys are higher than those of the corresponding crystalline alloys.

Crystallization and Corrosion Resistance of (Fe_(0.78)Si_(0.09)B_(0.13))100_(-x)Ni_x (x=0,2 and 5) Glassy Alloys

The crystallization of the （Fe0.78Si0.09B0.13）100-xNix glassy alloys （x=O, 2 and 5） has been investigated by X-ray diffraction （XRD） and differential scanning calorimeter （DSC）. Corrosion resistance analyses have been carried out using electrochemical measurements and corrosion products have been analyzed by scanning electron microscopy （SEM）. The experimental results show that the addition of Ni can promote the nucleation of c^-Fe, retard the decomposition of the metastable borides, and alter the crystallization mode of the present Fe-based glassy alloys. The lattice constant （ao^e） of c^-Fe in the annealed samples shows a decreasing trend with increasing annealing time. The Ni addition can improve the corrosion resistance of the as-quenched Fe-based glassy alloys in H2S04, NaCI and NaOH solutions. The results indicate that Ni can promote the diffusion of Si atoms during quenching and annealing processes.

Vibrational dynamics of Fe-based glassy alloys

The well recognized model potential is used to investigate the vibrational properties of four Fe-based binary glassy alloys viz.Fe_(90)Zr_(10),Fe_(80)B_(20),Fe_(83)B_(17) and Fe_(80)P_(20).The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves(PDC).Three theoretical approaches given by Hubbard-Beeby(HB),Takeno-Goda(TG)and Bhatia-Singh(BS)are used in the present study to compute the PDC.Six local field correction functions proposed by Hartree(H),Taylor(T),Ichimaru-Utsumi(IU),Farid et al.(F)and Sarkar et al.(S)and Sarkar et al.’s local field factor(SLFF)based excgange and correlation function are employed to see the effect of exchange and correlation in the aforesaid properties.

Crystallization Kinetics of a High-zirconium-based Glassy Alloy：A DSC Study

The non-isothermal and isothermal crystallization kinetics of Zr_（72.5）Al_（10）Fe_（17.5） glassy alloy was investigated using differential scanning calorimeter（DSC）.Under non-isothermal heating condition,the primary phase in the initial crystallization is Zr_6Al_2Fe phase and the final crystallized products consist of Zr_6Al_2Fe,Zr_2Fe and a-Zr phases.The apparent activation energy for crystallization estimated using the Kissinger method is 342.1 ±8.1 kJ/mol.The local activation energy decreased with the increase in the crystallization volume fraction during nonisothermal crystallization.Under isothermal heating condition,the average Avrami exponent of about 2.76 implies a mainly diffusion-controlled three-dimensional growth with an increasing nucleation rate.The local activation energy for isothermal crystallization shows a different variation trend from that for nonisothermal crystallization,indicating different nucleation-and-growth mechanisms for the two crystallizaiton conditions.

Effect of repeated melting of the mother ingot on the thermal stability of a Zr6oAl15Ni25 bulk glassy alloy

The effect of repeated melting of the mother ingot on the thermal stabilityof a Zr_(60)Al_+(15)Ni_(25) glassy alloy was investigated by differential scanning calorimetry(DSC). Experimental results indicate that after the repeated melting of the ingots at 1300 and 1580K, the glass transition temperature T_g increases from 686.4 to 690.7 and 696.8 K and the onsettemperature of crystallization T_x from 757.9 to 758.6 and 763.4 K, respectively, indicating thatthe thermal stability becomes higher after the repeated arc melting of the mother ingot and that itis more effective at higher temperature. Within the framework of structure heredity, the origin ofthe improvement of the thermal stability of Zr_(60)Al_+(15)Ni_(25) bulk glassy alloy is discussed.

Phonon dynamics of glassy copper alloys

The well recognized model potential is used to investigate the phonon properties for five glassy Copper alloys viz.Cu_(57)Zr_(43),Cu_(60)W_(40),Cu_(33)Y_(67),Cu_(43)Ti_(57) and Cu_(66)Ti_(34).The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves(PDC).Three theoretical approaches given by Hubbard-Beeby(HB),Takeno-Goda(TG)and Bhatia-Singh(BS)are used in the present study to compute the PDC.Five local field correction functions proposed by Hartree(H),Taylor(T),Ichimaru-Utsumi(IU),Farid et al.(F)and Sarkar et al.(S)are employed to see the effect of exchange and correlation in the aforesaid properties.

A detailed study of metallic glass formation in copper-hafnium-titanium alloys

Recently we have reported a number of bulk glass forming compositions in the CuHf-Ti system,with the critical thickness for complete glass formation,dc,ranging from 2 mm to 4 mm.In order to improve the glass forming ability （GFA） getting even larger dc,the prevailing approach is to use complex multicomponent systems.This strategy has been investigated by us for the Cu-Hf-Ti bulk glass forming alloy Cu55Hf25Ti20 using 〉1 at.pct additions of B,Y,Nb,Ta,Al,Mn,Si or V but with no significant improvement in the GFA.Clearly,it is necessary,in order to utilise the full potential of the base ternary system,to identify the best glass-forming compositions as a basis for extending the search into multi-dimensional compositional space.Thus,CuxHfyTiz alloys,where x=（40-70） at.pct,y=（5-30） at.pct,and z=（10-36） at.pct,were prepared by melt spinning andcopper mould suction-casting.The composition dependence of the GFA for the Cu-Hf-Ti alloys,as measured by dc for rod and ribbon samples,is reported over the composition range given above.

Crystallization of Al-based Amorphous Alloys in Good Conductivity Solution

The corrosion-induced crystallization of Al94 exNixGd6（x=6 and 10, in at.%） metallic glasses as well as phase separation, oxidation and cracking in good conductivity solution has been investigated by various techniques.The transmission electronic microscopy（TEM） result reveals that crystalline intermetallics and oxides present on the electrochemically thinned hole edge, and the phase separation occurs in the matrix of the as-spun ribbons with the circumferential speed Rcof 29.3 m/s. In addition, the bending and cracking of the samples occur after corrosion. The influence of Ni content on the phase separation, bending and cracking can be explained by the fact that the percolation of the backbone clusters in the amorphous alloy melts and glasses is enhanced by increasing the composition of Ni.