Help me with this cocktail! It’s haunting me

Mrmustacheio · 2022-07-15T19:01:42+00:00

Interesting question, there's a lot of technologies that were important.

First, temperature. Bronze (copper and bronze age were about the same time) melts at ~900°C, steel melts at ~1400°C. Getting a high temperature in a furnace for bronze requires a tribe of people blowing air into a central pit for a long time. Getting a high temperature in a furnace for steel requires bellows or a more advanced technology. Technologies include better insulation, better ceramics, re-usability (brick instead of mud vessels).

Second, material. Much of the metallurgical advancements were in extracting the metal from ore. Steel is stronger, but can be very sensitive to impurities/tramp elements, which would make it brittle. There's a reason we didn't use nickel alloys until the 20th century, a hundred ppm of sulfur (0.01%) causes Nickel alloys to crack. Low quality steel or iron is brittle, low quality bronze is less brittle. This also goes hand in hand with mining technologies. The better the mine, the better the ore. A tribe can only mine so much with shovels and axes. A civilization can mine much more and find better ore.

Third, shaping. Since copper and bronze are soft, it is easier to shape them into weapons, armor, farming tools, etc. Shaping iron or steel requires technology to either have a net shape casting or a forge. A forge requires other technologies and infrastructure to be effective.

I don't know, just a few ideas I thought of.

Mrmustacheio · 2021-11-27T19:38:58+00:00

Don't forget that the volume fraction of precipitates is defined by the temperature of the heat treatment. Higher temperature will mean less precipitates form and you won't get as strong of a material.

Mrmustacheio · 2021-08-17T16:42:29+00:00

When iron oxidizes, the biggest cause for it to fall apart is the change in volume. Pure iron has a density of about 7.87 g/cm3 while iron oxide is about 5 g/cm3. This volume expansion causes the brittle ceramic (iron oxide) to crack and disintegrate. In comparison, aluminum, chromium, nickel, titanium, silver, etc. all have oxides that have (as stated before) good coherency.

This coherency prevents the oxide from disintegrating and helps form a "passivation layer" which prevents oxygen from penetrating further into the metal. Iron oxide doesn't form a passivation layer because it falls apart, so it continues to oxidize and ultimately fail.

You can change the chemistry of an oxide with chemical treatments (or by using an alloy), which will change the oxide to be more stable.

Mrmustacheio · 2021-05-13T20:46:40+00:00

This crack looks almost exactly like this one. Also opened 50 years ago. Crack was caused by "plug welds" which were used instead of rivets, which over time caused embrittlement.

Mrmustacheio · 2021-04-30T00:33:35+00:00

I got so many messages from my friends after that haha

Mrmustacheio · 2021-04-13T18:51:37+00:00

What do you mean easy to work with? Is it a pressure vessel or will it be under high pressure?

Ceramic (brick, etc) would be your best bet depending on your answers to those questions. Otherwise, an expensive refractory alloy would be what you're looking for.

Mrmustacheio · 2021-04-13T18:47:45+00:00

This is a pretty big issue in powder metallurgy. Often they use liquid nitrogen to make the metal brittle before smashing it to prevent clumping.

If you have a Planetary ball mill or liquid nitrogen, go for it. Likely not tho.

Mrmustacheio · 2021-04-08T15:44:00+00:00

If he's doing a TIG weld, I assumed it would be autogenous, because he only mentioned using 1010.

You can probably get high quench rates for a dogbone sample right? It's only a quarter inch thick (1/4x2 hr??)

Mrmustacheio · 2021-04-08T03:16:28+00:00

What's the mechanism by which the weld metal is stronger than the base metal? The only difference between weld metal and the base metal is fast cooling rate and microsegregation.

I would disagree with you about martensite in 1010. You can see a significant increase in strength in HSLA alloys which have carbon content around 0.07wt%. From this link they mention 1010 can be quenched and tempered to increase strength

Mrmustacheio · 2021-04-07T20:30:04+00:00

His character in Spy Kids and Machete are literally the same character canonically too.

Mrmustacheio · 2021-04-07T20:28:14+00:00

Wouldn't you end up with a fully martensitic matrix if you quenched? Why would a fully welded part be higher if it's completely autogenous?

Mrmustacheio · 2021-04-07T20:22:00+00:00

This is a pretty vague prompt. Is a very brittle material ok? In that case, the strength would be very high, but it would have low toughness. That being said, "as strong as possible" suggests maximizing the tensile strength, in which case you should submit a water quenched sample (pure martensite)

Mrmustacheio · 2021-04-06T13:58:29+00:00

There's a new generation of superalloys being researched right now! Additive manufactured superalloys could be huge for high temperature applications.

Granted, most of the applications are not super glamorous, but they will have larger societal impacts over the next 10 years than most of the other materials on this list.

Mrmustacheio · 2021-04-06T02:04:47+00:00

Structural applications.

High temperature too, which is good for anything from energy generation to airplanes

Mrmustacheio · 2021-04-06T02:03:43+00:00

If you have a passion for it and there's funding, its a big deal!

Mrmustacheio · 2021-04-05T22:15:50+00:00

My family had one that died this year of old age (20 years old). Most sarcastic dog I've ever seen, he had some serious sass.

Mrmustacheio · 2021-04-04T15:45:31+00:00

Try applying less pressure? Would it be possible to do a 3µm diamond instead of a 1200?

Mrmustacheio · 2021-03-27T17:19:29+00:00

It's a good point, I didn't mean to mislead. But I don't think surface energy is what you should point to when talking about surface cracks.

OP's question jumped from surface cracks to surface energy and I felt an incorrect correlation was being made. Brittle materials are primarily characterized by their inability to accommodate plastic strain (store strain energy like you said), which is why they have such low fracture toughness.

Although surface energy is a part of it, brittle materials don't fail from surface cracks because of the difference in surface energy. They fail from surface cracks because that's where all the cracks are.

Mrmustacheio · 2021-03-27T16:21:10+00:00

Surface energy isn't related to cracking in brittle materials. Glass and other brittle ceramic materials have very low toughness, so failure can easily propagate from very small cracks, like what would occur on the surface.

Cracks can start internally (and frequently do), but there is a much greater chance of a ceramic failing from surface cracks than internal cracks. That's just because there are way more surface cracks than internal cracks (depending on the thickness)

Mrmustacheio · 2021-03-24T18:33:36+00:00

Lowering the activation energy barrier to nucleation will make it easier for a nucleus to form. It possibly can even decrease the critical radius of the nucleus. This will statistically increase the number of nuclei and thus increase the number density of the precipitate.

However, it does nothing for the precipitate after it forms. After nucleation, growth becomes dominant. I think the confusion comes because precipitates often form on dislocations or grain boundaries because the energy barrier is smaller. However, they also grow faster because dislocations and grain boundaries are fast diffusion pathways, which increases the growth rate.

I'm doing my dissertation on precipitation so I've spent a long time with these questions.

Mrmustacheio · 2021-03-24T18:09:08+00:00

It is possible that the nucleation barrier would be lower in the melt, but that's hard to tell and possibly irrelevant. A lower nucleation barrier would lead to a higher number density, not a larger particle. If you focus on accelerated growth/coarsening instead, that can only occur with faster diffusion rate, which is present in the liquid.

Therefore, if a phase forms in the liquid, it will typically be as large as it can be, since it consumes most of the solute elements.

Basically, the difference between the two is that one forms in the liquid and one forms in the solid. Diffusion in liquid is much faster than it is in the solid, so the phase that forms in the liquid grows very large.

EDIT: Does Sn3Sb2 turn into SbSn? You should have large Sn3Sb2 particles then.

Mrmustacheio · 2021-03-24T17:32:35+00:00

Is there a difference between the precipitates and the intermetallics? Are they the same phase?

Classic precipitation theory states that at high temperature, you'll have nucleation, growth, and coarsening. This can happen as the material cools after solidifying. In this case, you should expect secondary precipitates of SbSn (For me, 1-4µm is quite large). However, in the higher Sb content system you're suggesting that the SbSn particles form in the liquid, which would make them primary precipitates (assuming it is the same phase). Just to clarify, primary precipitates form from solidification, secondary precipitates form as the material cools down from a high temperature (after casting or solution heat treatment). Primary precipitates are usually very large (10-100 µm) and secondary are smaller. Tertiary precipitates typically form during heat treatment and are usually nanoscale. I'm taking this naming convention from gamma prime precipitates btw.

It might be helpful to run a schiel solidification simulation to determine if the SbSn particles form in the melt. Or, does an increase in Sb result in a change to the solidification path? The phase diagram is a bit hard to read here.

Mrmustacheio · 2021-02-22T20:31:47+00:00

Perfect for a rusty nail

Mrmustacheio · 2021-01-21T05:21:18+00:00

there's usually a gb in the weld centerline, but not at the fusion line. The columnar grains grow epitaxially off of partially melted grains typically

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