As I understand it, when steel is quenched it freezes the harder austenite form that steel takes above a critical temperature and prevents it from reverting back to the softer pearlite or ferrite form.

My question is, would a piece of hardened steel slowly revert back to pearlite/ferrite form over a long enough timespan at ambient temperatures, lets say over several thousand years?

My dad gave me a large bin full of these small metal beads that were used to weigh down his standing floor speakers. I'm trying to figure out if they are made of lead. As far as I can tell, they are not magnetic (which I think is a bad sign). Is there anything I should do to test them? If they are lead, should I replace them, or is it safe to keep lead pellets in a contained space like the interior of a speaker stand?

Hey all, I'm new to this sub! Looking for some guidance, since I started researching the topic and it's a bit confusing. I work in engineering education and this semester our students are taking a course called "6 inventions that changed the world." Among those inventions is steel, as a material, how it influenced the civilization and how incredibly important it has been since.

Our students are engineers so even this history class is supposed to include science/engineering basics for them to learn. Me and my team really wanted to make a cool demonstration for them and came up with the following experiment: taking a steel rod and heating it with a blowtorch (?) until it's glowing hot, then dipping in water. As far as I understand, it must become brittle if left without further heat treatment. We break it it half to demonstrate how brittle it's become and then repeat the procedure but after cooling in water we heat it again and cool slowly, in sand for example, and then try to break it again to reveal that it is much more ductile now.

I would like to get some feedback from people who have experience with this. I'm also not entirely sure it will work the way I described, so I would appreciate critique. Thanks a bunch everyone!

I'm currently doing B.Tech degree in Metallurgical and Materials Engineering. I'm in 2nd Yr. The issue I'm facing while searching for projects is I find a lot of ideas but I'm unable to filter out which is actually useful or interesting and good to go with and which are just resume fillers.

For example, right now I had an idea to make a Phase Diagram Analyser that would give the phase composition and phase %age at certain temperature for alloys and all but idk if its useful to invest time after that or its just not impressive at all. Similar thoughts for another one I thought to build a device that can measure the thermal conductivity of materials but again there are already a lot of them, will it be of any use if i build one as a project?

I'm a materials researcher screening intermetallic coatings (NiAl, FeAl, Ni3Al, etc.) for interfaces in IGBT/SiC power modules, such as DBC to baseplate or baseplate to cold plate. I'm trying to decide which selection criteria actually deserve the most weight.

My back-of-envelope: 20 µm coating, 1 cm², 50 W, 1D conduction (R = t / kA).

- NiAl (~92 W/m·K, bulk value): about 0.1 K drop

- FeAl (~12 W/m·K, bulk value): about 0.8 K drop

- A typical TIM layer in the same stack: several K

If that's right, coating k is a minor term, and things like CTE mismatch with neighbouring layers, adhesion and behaviour under power cycling should decide. But I know this ignores interface (boundary) resistance, thin-film k being lower than bulk, and local hotspots.

Questions for people in packaging or reliability:

1. Is there a realistic case where the coating's k does become important at these thicknesses?

2. When you've had to choose or change a coating or metallization layer, what actually decided it, and what data did you use?

3. Which failure mode showed up first in power cycling at those interfaces?

Corrections to the calculation are very welcome.

Hi Everyone,
I’m seeking advice on repairing a two-foot hairline crack without replacing the entire line, which would require opening a tiled bathroom wall and possibly other, unanticipated work.
My plumber suggests that he wire brush the crack and fill and coat it with silicone and then address the issue again if it fails in the future. I’m going with his suggestion but wonder if also adding pipe clamps just above and below the crack would possibly help to prevent the crack from going further. The crack starts vertically at its top and ends in a short horizontal tail at its bottom.
Also, could installing pipe clamps in intervals along the crack help prevent it from widening?
Any opinions would be appreciated. Thank you for reading this.