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The finding of Jang and Koch that the melting enthalpy/mass, ΔHm, of a Sn matrix containing a fine dispersion of Ge particles sharply decreases with increasing Ge volume fraction, νGe, >0.5 and vanishes at νGe = ν°Ge ≍ 0.81, is accounted for by supposing that the Sn is distributed between an interfacial and bulk state. The interfacial statc is one in which the Sn is assumed to be in a disordered, possibly amorphous, structure coating the Ge particles uniformly to a constant thickness, δ. The remaining “bulk” Sn is assumed to exhibit the normal enthalpy of fusion, ΔH°m. The model accounts for the dependence of ΔHm on νGe within the experimental uncertainty. With the average width of Ge particles −10 nm, δ is estimated to be −0.23 nm; i.e., of the order of the thickness of one Sn monolayer.

While most amorphous alloys have been prepared by rapid quenching from the liquid state or quenching from the vapor state, there has been recent interest in solid state amorphization. High energy ball milling of powders is a solid state amorphization method that can synthesize amorphous alloys by mechanical alloying (MA) of elemental powders or by mechanical milling (MM) of intermetallic compound powder. It is emphasized from the present observations of Tg's in Cu/sub 1-chi/Zr/sub chi/ alloys and previous work of Ni/sub 1-chi/Zr/sub chi/, that amorphous alloys prepared by MA or MM can be amorphous rather than microcrystalline. When the authors account for the effects of impurities (oxygen or iron), the T/sub g/ values are essentially identical to those for amorphous rapidly solidified alloys of the same composition (i.e. Cu/sub 50/Zr/sub 50/).

A melting point depression, δTM, has been observed for Sn in Ge/Sn (50 at.% Sn) dispersions which were prepared by mechanical milling of Ge and Sn powders. Sn and Ge are immiscible and form a fine dispersion of the pure components when milled in a high energy ball mill. The magnitude of δTM, as measured by DSC, increases with milling time, i.e., with refinement of the dispersion. Melting is observed to begin as low as 36 °C below the equilibrium bulk melting temperature. The magnitude of δTM is reduced by about 25% after melting the Sn. Subsequent remelts do not change δTM further. Impurities cannot account for δTM. While stored energy of cold work may contribute to 25% of δTM before Sn is melted, it is concluded that the major contribution to δTM comes from the nucleation of disorder/melting at the Ge/Sn interfaces.

This paper reports selected results of a continuing study of the systematics and mechanisms of amorphization by mechanical alloying of mixtures of intermetallic compound powders. Mechanical alloying was carried out on mixtures of “line” intermetallic compounds ( i.e . those having a narrow range of homogeneity) in the following binary alloy systems: Cr-Ti, Mn-Ti, Cu-Ti, Fe-Ti, Co-Ti, Ni-Ti, Cu-Zr, Ni-Zr and Mn-Si. Amorphization by mechanical alloying was observed to be complete, to the resolution of X-ray diffraction, for intermetallic compound mixtures ( e.g . NiZr 2 + Ni 11 Zr 9 → a-Ni 40 Zr 60 ) in all the above systems except Cr-Ti, which exhibited partial amorphization, and Mn-Si, which showed no amorphization. The amorphization tendencies could not be predicted from calculated enthalpies of mixing for the amorphous alloys, all of which were negative, or from calculated differences in free energy between the amorphous phase and the mixture of equilibrium intermetallic compounds. Preliminary transmission electron microscopy studies of the evolution of the amorphous phase for the system NiZr 2 + Ni 11 Zr 9 → a-Ni 40 Zr 60 revealed an amorphous halo-like region surrounding the transforming intermetallic particles in an amorphous matrix. Energy dispersive X-ray analysis measurements indicate that the halo-like region has a composition which falls between those of the intermetallic particle and the amorphous matrix.

Zr 61 Al 7.5 Ni 10 Cu 17.5 Si 4 (ZrAlNiCuSi) thin film metallic glasses (TFMGs) can modify the surface of 304 stainless steel, and they are widely used in health care systems. We investigated modified surfaces with ZrAlNiCuSi TFMGs and their antimicrobial effects on those five microbes which are the most common nosocomial infection pathogens. The transformation of ZrAlNiCuSi bulk metallic glass into TFMG was achieved by sputtering onto stainless steel. Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii and Candida albicans were then isolated. The microbes were sampled on ZrAlNiCuSi TFMGs, and this was compared with stainless steel plates. After microbe-material interaction under humidity at room temperature for 3 hours, the specimens were attached to a Mueller-Hinton agar plate (Gibco, Middleton, WI, USA) and incubated at 37.0°C for 24, 48 and 96 hours. The areas of microbe growth were recorded by serial subtraction photography and then assessed using Image-Pro Plus software (Media Cybernetics, Bethesda, MD, USA). ZrAlNiCuSi TFMGs presented an amorphous rough surface and exhibited hydrophobic properties. ZrAlNiCuSi TFMGs suppressed E. coli growth on Mueller-Hinton plates for 96 hours, and there was no E. coli growth on blood agar plate enriched media and eosin-methylene blue agar selective media after 96 hours of incubation. The five microbes tested on ZrAlNiCuSi TFMGs showed a decreased growth curve after 24 hours. After 24 hours, P. aeruginosa showed a slow growth curve and A. baumannii had a sharp growth curve with TFMG interaction. ZrAlNiCuSi TFMGs prolonged the lag phase of the microbes' growth curve in S. aureus and C. albicans for 48 hours. ZrAlNiCuSi TFMGs were able to modify the surface of stainless steel, which was very hard and was found to have scratch adhesion abilities and smooth surface effects against five different microbes for at least 24 hours. This is the first description of microbe interactions with zirconium-based TFMGs. Further studies to investigate the mechanism of antimicrobial effects on ZrAlNiCuSi TFMGs are now required.