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Offline Enthalpy

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Amorphous Alloys
« on: May 20, 2023, 07:35:59 PM »
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

Offline Enthalpy

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Re: Amorphous Alloys
« Reply #1 on: May 21, 2023, 05:25:20 PM »
========== 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.

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Offline Enthalpy

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Re: Amorphous Alloys
« Reply #2 on: May 23, 2023, 05:55:00 PM »
========== 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

Offline Enthalpy

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Re: Amorphous Alloys
« Reply #3 on: May 27, 2023, 05:37:06 PM »
========== 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

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Re: Amorphous Alloys
« Reply #4 on: May 28, 2023, 08:21:11 PM »
========== 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 4/5th 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 Tc=290K at Pc=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.

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Re: Amorphous Alloys
« Reply #5 on: May 30, 2023, 03:27:33 PM »
========== 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

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Re: Amorphous Alloys
« Reply #6 on: June 03, 2023, 06:52:24 AM »
========== Gears and chains

They use rounded contacts between the teeth, and need excellent wear resistance and friction: gears should try amorphous alloys, especially Medalium N1. Ams mentions that already. N1 can be a layer or solid.

Only the low heat conduction is unfavorable, but the lubricant removes the heat usually.

Transmission chains need similar properties.

========== Plain bearings

As they report good friction properties, amorphous alloys might make plain bearings too, again as a layer or solid.

The low heat conduction is unfavorable but some uses don't need it. At cranes and other heavy machines, some joints move very slowly and briefly but would benefit from a higher contact pressure.

Bronze or polymer plain bearings are often sintered roughly from a powder to be porous and carry oil, grease, graphite, MoS2, Ptfe and more. A powder fits nicely the quick cooling needed by amorphous alloys.

I vaguely suppose that extreme hardness isn't desired, and that the mating faces should be ground after sintering, possibly in a preferred direction.

========== Fast rotations

Some machines rotate with big azimuthal (linear) speed. Steam and gas turbines do because their working fluid is fast and reacts to the linear speed. Water turbines are slower but they pay for strong alloys too.

The shape of the parts matters and answers many demanding desires, while the material multiplies the break speed by (σ/ρ)0.5: yield strength over density. This figure-of-merit is the azimuthal speed that breaks a thin ring. (2σ/ρ)0.5 breaks a uniform radial rod, thin blades held by a thick shaft achieve a bigger multiple of (σ/ρ)0.5.

          |   Z1     T1     N1   | CrNiMo12  Ti-662  18-12-5   Carbon
======================================================================
σ  MPa    |  1700  ≈2000  ≈3000  |    800     1100     2400    ≈1400
ρ  kg/m3  |  6620   5900   8500  |   7700     4540     8083     1550
======================================================================
   m/s    |   507   ≈582   ≈594  |    322      492      545     ≈950       
======================================================================


CrNiMo12 is the 1.4938 for steam turbines, 18-12-5 is a NiCoMoTi maraging steel, and "Carbon" a composite of strands laid in optimized directions.

* Against creeping, high- and low-pressure turbine stages will retain Ni and TiAl alloys.
* Turboprop have already graphite fans with metal protection at the leading edge.
* They use Ti alloys to resist bird impact: turbofans could have fans and early compressor stages of amorphous alloys. Impact strength matters, pure strength and density too. Especially Medalium T1 could outperform present Ti alloys.
* Pressured-water reactors provide saturated steam at ≈280°C that condenses partially in the HP turbine. Docs don't tell how much they creep, but amorphous alloys at steam turbine blades might better resist eroding water droplets that cost downtime, inspections, replacement.
* Sand in water erodes dams blades, corrosion does the rest, costing maintenance too. Amorphous alloys might make better dam turbines when big parts become possible.

========== Strength and low conductivity

Some heavy aggregates must leak little heat: a boiler, a cold detector at a telescope, etc. Once the design uses only tensile and compressive wires, rods and tubes, a material's figure-of-merit σ/K remains, strength over heat conductivity, and amorphous alloys are good for both. A few uses need a low electric conductivity instead.

          |   N1   | Ti-Al6V4  17-7 PH   Glass  Aramide
========================================================
σ    MPa  | ≈3000  |   830       2300     550    >2000
K  W/m/K  |   ≈10  |   6.6         16     0.5     0.05
C   MS/m  |  0.63  |   0.59       1.2       0        0
========================================================
σ/K       |  300M  |   126M      144M     1.1G     40G
σ/C       |  4.8k  |   1.4k      1.9k      -       -
========================================================


The spring stainless steel 17-7 PH exists as wires and strips that could make tubes. "Glass" is a composite of glass fibre strands, 550MPa its compressive strength. Aramide composites resist little compression, data is for unimpregnated strands under tension only. Pbo, Lcp might be even better.

Suspending an aggregate with polymer strands or glass fibre tubes is uneasy. Amorphous alloys are the best metals to hold and insulate an aggregate.

I proposed to zap a wire to discard parts no longer needed, there
  scienceforums
Amorphous alloys excel at all aspects. A D=0.5mm L=10mm wire of Medalium T1 holds ≈400N, <3J zap it while air loses <2.5W and conduction <1W so 0.5s×0.9V×11A suffice, provided by one common 1g supercapacitor or an NiCd accumulator. Or zap faster with an alu capacitor.

At other alloys too, when electrons conduct little heat, the matrix matters much. So I propose to replace a good part of Nb and Zr by Ta and Hf when amorphous alloys shall conduct less heat.

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Re: Amorphous Alloys
« Reply #7 on: June 04, 2023, 01:22:25 PM »
========== Massive parts

Some uses need thick short material, inconvenient to roll or extrude: the equivalent of forged material.

On the left part of the sketch, I propose to drip the molten amorphous alloy through many nozzles. The drops cool by contact with the existing material which is cooled by many jets of fresh gas. Small movements of the growing part spread the drops. 50kW/m2 are easily removed, allowing 0.1m/h growth rate.

On the right part, a spatula or a roll presses an even new thickness of material on the existing one. Fresh gas cools everything then, and cyclic movements let iterate the next layer. Or the existing and new material are brought in contact with the wall of a liquid cooler before iterating. This removes heat about 100× faster, which could grow the amorphous alloy by 0.1m/min if the melting power is available. Hydraulic actuators can provide peak power for the pumps and movements. That option can operate in vacuum.

If cooling gas gets trapped in the material, H2 or He would diffuse out below the glass transition temperature. They are efficient coolants.

The produced material probably needs compaction, already to remove the internal stress. The material is hard and the temperature limited. A forge press could get smaller and harder facing parts, maybe of carbide-loaded tool steel.

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Re: Amorphous Alloys
« Reply #8 on: June 29, 2023, 03:56:59 PM »
========== Blades

Amorphous alloys might make decent stainless blades for knives, scissors, shavers, surgery tools and more.
  • Specialized stainless steel X90CrMoV18 and X105CrMo17 offer only 60Hrc, roughly equivalent to 2400MPa strength. X40Cr13 is worse.
  • Ams claim 4500MPa bending strength from their Medalium N1 (Ni-Nb38) alloy.
  • C1 (Cu-Ti34Zr11Ni8) shall offer 2900MPa with "excellent" ability to polish, T1 (Ti-Zr35Cu17S8) too.
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Re: Amorphous Alloys
« Reply #9 on: July 12, 2023, 11:24:18 AM »
One more use for amorphous alloys?

========== Punch and die for a punching press

  Punching at Wiki
Medalium N1 from Ams is hard enough. Smoothness and dimensions accuracy still need grinding and spark gap erosion to make the final surface of the punch and die, but amorphous alloys enable additive manufacturing to achieve near-net shape and save much time at spark-gap erosion.

Cnc presses tend to use standard tools many times to achieve special part shapes, but custom tools improve the part smoothness and the productivity.

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Re: Amorphous Alloys
« Reply #10 on: August 03, 2023, 11:12:56 AM »
========== Circlip

Their shape can't adjust much the part's elasticity, so amorphous alloys would bring dimensions or behaviour different from steel
  wikipedia
Corrosion resistance is welcome too. I know only phosphated parts up to now, not desired in vacuum for instance.

========== Electrical connectors

Liquidmetals mention already "severe duty connectors for automotive" but all connectors need individual springs to ensure good contacts and to even tolerances out.

For instance computers need 90 reliable contacts at Pci-e, 250 at Dram modules, 4000 at some Cpu. Room, electrical performance and production processes leave little freedom to the spring design, so new materials are interesting.

Beware the contacts demand a very adherent gold layer. Does this still justify brass and bronze? Zr, Ti, P in amorphous alloys don't help.

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Re: Amorphous Alloys
« Reply #11 on: August 04, 2023, 10:13:38 AM »
========== Metal bellows and couplings

Since amorphous alloys claim a huge elastic strain and low losses, they should excel at repetitive deformations. This fits metal bellows and shaft couplings:
  Metal bellows - Metallbalgkupplung at Wikipedia

Some couplings are electroformed, other shapes and thicknesses can be injected.

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Re: Amorphous Alloys
« Reply #12 on: August 06, 2023, 07:47:20 PM »
Amorphous alloys combine high strength with low stiffness. If they resist more bendings and give more deformation energy back, they can outperform steel and polymers as:

========== Tyre reinforcement wire

========== Belt reinforcement wire

For belts toothed ot not
  wikipedia

Amorphous metals might even provide closed loops of wire to these two uses.

========== Metallic belts

They're preferred for stiffness, say to move printer heads. Amorphous metals belts could accept smaller pulleys than thin electroformed nickel does.

Hey, don't forget the musical strings! Music makes us human, and amorphous metals can make a bigger difference at strings.

Marc Schaefer, aka Enthalpy

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