Talk:Amorphous metal

message: The article asserts that upon reheating amorphous metals start to flow. I believe that this is slightly misleading, it is a well known phenomenon that heating amorphous metals will cause them to recrystallise, at least in part, and take on the more stable form, i.e. a crystal. Where did the concept of reheating the glass to make it flow come from? 129.78.64.106 01:42, 12 October 2006 (UTC)
replies: text: How easy an amorphous metal crystallizes depends a lot on the composition. A few are so stable that they can be heated above the glass temperature without fast crystallization. Other alloys crystallize before they become really soft.Ulrich67 (talk) 19:52, 26 May 2022 (UTC)
replies: text: Very true. I learned a lot about metallic glass from mirror manufacture, because mirror coatings are amorphous, whether applied by vacuum deposition, wet deposition, electroplating, or fire gilding. Turns out, if the coating is too pure the metal can crystallize even when below the glass transition. In vacuum deposition, for example, some of the gas atoms become trapped in the amorphous network, which act like throwing a monkey wrench into the works to help prevent recrystallization. This actually increases reflectivity in the visual and NIR range, but for FIR mirrors a much higher vacuum can produce almost pure coatings which help enhance reflectivity but is not affected by recrystallization at that wavelength, due to the wavelength being larger than the crystals. Zaereth (talk) 20:16, 26 May 2022 (UTC)
thread_title: Reheating

message: http://www.sciencedaily.com/releases/2008/12/081219172129.htm --24.96.180.121 (talk) 00:46, 28 December 2008 (UTC)
thread_title:  titanium glass 

message: The article needs to indicate how the electrical conductivity compares with crystalline metals. Most probably the lack of periodic wavefunctions will cause the resistivity to be higher, but by how much?  —Preceding unsigned comment added by 193.188.46.249 (talk) 08:00, 18 March 2010 (UTC)
replies: text: For the ferromagnetic alloys two manufacturers give values of about 1,2 -1,4 µOhm m. Refs: , . This is about two times the resistivity of stainless steel. About the same ration should be valid for the thermal conductivity, as the Wiedemann-Franz law should be a reasonable approximation for the amorphous state as well. --Ulrich67 (talk) 20:26, 17 August 2011 (UTC)
thread_title:  Electrical Conductivity 

message: Shouldn't we have a list of amorphous metals as a new topic? The page describes about amorphous metals, but does not have a list of them. Valchemishnu 15:46, 17 June 2011 (UTC)
replies: text: Amorphous Metals are a quite special topic, with not so much general interest. Except for specialists there is not much use of such a full list of alloys. One Problem with such lists is, that we may need a ref. for nearly every entry. Maybe if we limit the list to those alloys with real world applications it may be of some general interest.--Ulrich67 (talk) 19:39, 8 August 2011 (UTC)
thread_title:  Shouldn't we have a List of Amorphous Metals? 

message: The article has left out another perhaps interesting method for obtaining metals in an unusually glass-like form:  electrodeposition.   I know, because I've plated amorphous Nickel and verified its amorphous structure with x-ray diffraction as an undergrad physics project.  I'd also like to point out, that I quite agree with an earlier post about the lack of information about the conductivity of metallic glasses.  Whenever the properties of any metallic material is considered, conductivity is one of the first that comes to mind.  Bu7fkl7 (talk) 04:25, 17 August 2011 (UTC)
replies: text: A section on the methods to produce amorphous metals would be a good idea. There are a view other methods: electroplating, ball-milling, heavy irradiation, inter-diffusion, Thin film deposition.  — Preceding unsigned comment added by Ulrich67 (talk • contribs) 21:15, 16 September 2011 (UTC)
thread_title:  Another way to make met-glass 

message: I disagree with the statement under Properties, "The absence of grain boundaries, the weak spots of crystalline materials..."  Grain boundaries are a strengthening mechanism of pure metals, alloys and ceramics, not weak spots.  Grain boundary strengthening works by being a barrier to dislocation motion, as quantified by the Hall-Petch equation.  The exception to this rule is  creep, where grain boundary sliding enables deformation under constant load above ~0.5 homologous temperature.  Metal glasses, by virtue of not having a crystal lattice, cannot deform by dislocation movement.His Manliness (talk) 19:18, 30 November 2012 (UTC)
replies: text: Grain boundaries usually increase the mechanical strength, but they are also placed where corrosion often starts. So the grain boundaries are the weak spots with respect to corrosion. --Ulrich67 (talk) 20:13, 30 November 2012 (UTC)
replies: text: Actually grain boundaries are much weaker than the crystals themselves. This is why in heat treating efforts are used to keep the grains as small as possible, because the boundaries provide a place for a crack to form and a line for it to follow. In items that need exceptionally high tensile-strength and thermal resistance, the items may be cut from a single crystal, thereby removing all grain boundaries. A good example is the turbines of fighter jets. Zaereth (talk) 20:09, 16 February 2017 (UTC)

text: Here we go. As an example, bulk iron has a tensile strength of 180--250 MPa, yield strength of 14--103 MPa, and a Charpy v-notch of 200 joules. The individual crystals, on the other hand, have a tensile strength of 5000 and 13000 MPa (depending on crystal orientation) and a shear strength of 3500 and 8000 MPa. Zaereth (talk) 20:46, 16 February 2017 (UTC)
thread_title:  About grain boundaries 

message: I just read this article and found it to be very informative. I learned a lot, and thank those who put the time and effort into building it. My only observations are that it seems too focused on amorphous metals created by rapid cooling, and doesn't really mention non-mechanical properties like optical and electrical. Other methods for making amorphous metals exist, such as vacuum deposition, wet deposition, electroplating, or amalgam reduction. The reduction of amalgams is probably the oldest method, which has been used for mining precious metals for thousands of years. It was also applied to gilding and mirrors, because the reflectivity is much higher than crystalline metals. I don't know enough about the specifics to be any real help myself, but hopefully someone who does will read this and decide to help out. Zaereth (talk) 01:09, 16 February 2017 (UTC)
thread_title:  Other amorphous metals 

message: Intro says "amorphous metals have good electrical conductivity" (no ref) but the only other mention of electical conductivity is of high resistivity. What can we say ? - Rod57 (talk) 12:41, 30 March 2020 (UTC)
replies: text: From what I recall, metallic glasses have very good electrical-conductivity compared to insulators, but compared to crystalline metals of the same type the electrical resistivity is typically 3 to 6 times higher for metallic glasses. This is generally attributed to electron scattering due to the disordered atomic structure. A side effect is that this decreases inductance, skin effect, and the accompanying eddy currents, making them highly suitable for things like transformer cores with lower losses than iron cores. Another difference is that the resistivity is extremely temperature-dependent for amorphous metals. At extreme colds the conductivity will reach a maximum (resistivity reaches a minimum), and as temperature is further decreased the conductivity will decrease, which is usually attributed to the Kondo effect. In contrast, thermal conductivity tends to be higher in amorphous metals, due to their tendency to generate more phonons than crystalline metals, which tend to dissipate quickly in a crystalline lattice. I hope that helps. Zaereth (talk) 17:40, 30 March 2020 (UTC)
thread_title:  Electrical conductivity - high or low