[Enthalpy]

Hello nice people!

I used amorphous alloys in 1995 as the thin magnetic materials of antitheft strips, and in 2002 as extra-strong thick aluminium bars made by sintering thin flakes.
  wikipedia
  https://en.wikipedia.org/wiki/Amorphous_metal
Back then, the cooling rate that prevented crystallization resulted from the contact of alloy droplets with a spinning drum of cold metal.

New alloys accept slower cooling hence bigger thickness meanwhile, up to 5mm, so a pump can inject them in a cooled mold as for thermoplastics to obtain near-net shapes.

I found few manufacturers: Liquidmetal and Vitreloy who inherited the research at Caltech, and AMS (Amorphous Metal Solutions GmbH) who inherited the research at University of Saarland and belong now to Heraeus
  Liquidmetal and their Design Guide - Eutectix and their Datasheet - AMS and their Datasheet - Heraeus
Unusual combination of strength, low modulus, low heat conductivity, resistance to corrosion.

========== Diffusion barrier

Ams' Medalium Z1 takes far less volume than its constituents, others maybe too:
  59.3% Zr - 28.8% Cu - 10.4% Al - 1.5% Nb (understood as mass %)
The sum of the volumes suggests 6121kg/m³ while the datasheet announces 6620kg/m³, full 8% more.

Could it be more hermetic to hydrogen and helium? Nice for storage!

So the abnormally low Young's modulus and high density can coexist. First case I see.

========== Seals

Springs of amorphous alloys may well improve hydraulic seals. Presently, many seals include springs of (stainless) steel, for instance to press the polymer against the sealed surfaces until the fluid pressure does it. The big elastic deformation is very useful here. In warm watery fluids, resistance to corrosion is welcome. Existing injection machines suffice for many parts.

In piston engines and elsewhere, alloys make the seals themselves. The big elastic deformation is an improvement. This needs a non-galling material.

========== Strings

I have already suggested to make music strings of them. They seem strong enough, their elongation is badly desired, corrosion resistance is welcome.
  talkclassical and next

Marc Schaefer, aka Enthalpy

[Enthalpy]

========== Corrected density estimate

Ams' datasheet gives proportions in moles. For Medalium Z1, summed volumes and masses predict 6623kg/m³, the datasheet gives 6620kg/m³. No application expected from this normal density.

========== Short wires

Ams-Heraeus suggest only injection molding besides additive manufacturing. I hope the injection machine and a hole in the "mold" makes wires of limited length. They claim to inject 20g, this makes already 37m of D=0.32mm violin E-string, or 15m of 20mil string for a hammered dulcimer, or 6m of 32mil string for a cimbalum. Affordable trial!

========== Long extrusions

I understand the warm material isn't fluid like usual alloys but rather a thick paste like injected thermoplastics - or worse. The huge pressure must limit Ams-Heraeus to 3cm³. It's supposedly more difficult than aluminium profile extrusion, which uses a big piston.

I suggest to combine several small pumps in a cycle to inject a bigger part. Known hydraulic designs achieve 1500bar, I hope scaling fits an amorphous alloy injector. The illustration rotates a wedge, but independent pumps with electronic phasing can save hardware and be healthier. No, I didn't consider AI. And, such a lighter design might extrude usual alloys too.

Besides the displayed wire, other sections with thin walls might be possible. Tubes and hollow sections need a kernel hold in the matrix by pillars upstream, which may be feasible or not. Even very flat closed sections like sheets may demand pillars if they're extruded.

Does this sound simple? I suspect the powders must be heated in vacuum, and the amorphous alloy doesn't flow spontaneously in the pumps, and all forces are huge. Plus, the warm alloy shall not dissolve the machine parts, and so on.

Marc Schaefer, aka Enthalpy

[Enthalpy]

========== Cooling jacket

The cooling jacket of the machine for long extrusions in my previous message resembles that of a rocket engine. This can inspire the design, with a cooled internal wall hold by a strong cold one - but remotely, because some constraints are easier at the present matrix:

• The heat flux is much smaller, like 1MW/m², not 50MW/m². The materials can be stronger than copper.
• The inner wall can resist pressure at the temperature of the contents.
• Cylinders here are much easier to assemble.

However, the upstream pressure may very well exceed 500bar here.

========== Layer

It shall offer 900Hv hardness, 1.8% elastic elongation, resist abrasion and corrosion: try Medalium N1 (Ni - 38 Nb) as a protective and tribological layer!

For instance length-ground chromium serves at hydraulic pistons only because it wears seal rings less. Other properties aren't brilliant, especially, it's a badly galling material, which implies non-galling bearings that accept little contact pressure.

Many deposition methods provide naturally the fast cooling: Cvd, Lpcvd, e-beam, dipping... The base material can even be heated superficially so it cools quickly after receiving the amorphous layer.

Marc Schaefer, aka Enthalpy

[Enthalpy]

========== Thick extrusion in steps

To produce ice faster, I proposed to remove heat quickly at the newly formed face, not slowly through more and more thickness at the older face.
  chemicalforums
This shall apply to amorphous alloys too, so thick products get the needed cooling rate. Here for extrusions. Maybe, since many things can go wrong.

Each time thickness is added, the new amorphous layer is cooled, not too much so the next one builds a good interface. This may need vacuum or a rare gas or a reducing one, especially hydrogen. Separate pumps are displayed, common ones are less flexible.

The obtained extrusions will have a huge internal stress. Annealing is supposedly impossible, but traction through a dice releaves the stress, or as displayed here, compression by rolls. Optionally after intermediate steps too.

Marc Schaefer, aka Enthalpy

[Enthalpy]

========== Rolled products, stepwise thicker

As for extrusions, I propose to add thickness stepwise and cool it at the new faces.

The injection pressure is supposedly big. A slit wouldn't resist it, but many narrow nozzles do. Or at least, a slit needs reinforcements upstream, through the melt. The mill could be vertical if necessary.

The cooling power isn't huge. W=1m Δt=1mm Δx=0.1m in 1s need roughly 40kW per face, maybe 100kW if the melt is really hot. The rolls have a good contact and hard steel offers a heat impedance 4× smaller than the amorphous alloy, so the added thickness loses 4/5^th of its excess temperature if the rolls are well cooled: interesting option. The outer rolls bring bending stiffness, more stages are common practice.

The illustration suggests varied cooling means.

• Gaseous dry H₂, He, Ar should be harmless to the amorphous alloy. Blow well at the product or the rolls.
• Ar (cheap) is liquid at 90K (expensive) and 1bar. Liquid Xe exists up to T_c=290K at P_c=57bar.
• Flexible hairs or foils, say of Cu-Cr1Zr, collect by contact the heat for evacuation by an enclosed liquid or a blown gas.
• A flexible foot pressed against the product or the roll transfers the heat to a liquid. It follows the product's movement but leaves it at intervals to land further upstream.

Compression by rolls releaves the internal stress, at more steps if needed.

Marc Schaefer, aka Enthalpy

[Enthalpy]

========== Hertz' contact

If rounded parts press against an other, a lower Young's modulus E spreads the force on more area, and a big yield strength σ prevents permanent deformations. Useful at ball or cylinder bearings, and elsewhere.

Hertz (Heinrich, yes) gave models and formulas for spheres, cylinders and more, given in the excellent
  Dubbel, Taschenbuch für den Maschinenbau - available at amazon.de - amazon.com - and elsewhere
C:Festigkeitslehre > 4: Beanspruchung bei Berührung zweier Körper (Hertzsche Formeln) (Hertzian contact stresses)

The material's factors σ³/E² and σ²/E multiply the bearing capability of spheres and cylinders of given dimensions. This table compares the merit of Ams' amorphous alloys and other materials at round contacts.

          |   Z1     T1     N1   | C-steel   SSteel
====================================================
σ  MPa    |  1700  ~2000  ~3000  |  ~3000    ~2300
E  GPa    |    82     96    170  |    209      215
====================================================
Sphere    | 0.76M  0.87M  0.93M  |  0.62M    0.26M
Cylinder  | 35M    42M    53M    |    43M      25M
====================================================

Amorphous alloys may excel at round contacts, depending on better data. One manufacturer considers bearing races. Try balls, cylinders and needles too! The stress being shallow, amorphous alloys can be a layer on steel elements. Amorphous alloys resist corrosion and may outperform stainless steel and ceramic bearings.

The developers claim that Ams alloys show smaller losses than hardened steel. Bearings could rotate more easily, say to store electricity. Endurance is experimental.

========== Resist flat shocks

Density ρ and Young's modulus E define a material's wave impedance Z = (ρE)^0.5. A part losing a speed ΔV experiences a pressure wave P=ΔV×Z that deforms the part permanently if exceeding the yield strength σ.

The part design matters much and the material contributes the factor-of-merit σ/(ρE)^0.5. In my experience, yield strength lets survive repeated shocks, while resilience and damping are useless or detrimental, as for ball bearings or cyclic stress. I did not try truly brittle materials.

This table compares the merit of Ams' amorphous alloys and other materials upon flat shocks.

          |   Z1     T1     N1   | RSA-707  Ti-662  C-steel   SSteel
=====================================================================
σ  MPa    |  1700  ~2000  ~3000  |    850    1100    ~3000    ~2300
ρ  kg/m³  |  6620   5900   8500  |  ~2900    4540     7850     7700
E  GPa    |    82     96    170  |     71     116      209      215
=====================================================================
   m/s    |    73     84     79  |     59      48       74       57
=====================================================================

According to the table, these three amorphous alloys excel at shocks and they offer varied properties. They even resist corrosion.

========== Shocks at round parts

The direction of a shock is rarely accurate, so the parts are designed round. This table compares σ³/(E²Z) = σ³/(ρE⁵)^0.5 as approximate merits of materials at shocks between round parts.

          |   Z1     T1     N1   | RSA-707  Ti-662  C-steel   SSteel
=====================================================================
σ  MPa    |  1700  ~2000  ~3000  |    850    1100    ~3000    ~2300
ρ  kg/m3  |  6620   5900   8500  |  ~2900    4540     7850     7700
E  GPa    |    82     96    170  |     71     116      209      215
=====================================================================
Merit     | 0.031  0.036  0.025  |  0.008   0.015    0.015    0.006
=====================================================================

Amorphous alloys lead more here. Their corrosion resistance is welcome too, as shocks can burst a protective layer.

Marc Schaefer, aka Enthalpy