r/metallurgy

I was scrolling through my old posts and saw me complaining about the durability of steel bars in Project Zomboid and got curious. How many zombies could you Kill with this 28 inch long 1.5 inch diameter 4140 round bar before it would bend to the point it’s unsuitable to use as a weapon, or break entirely?

This is a 500 year old lead token that seems to be pitting. Is there anyway the pitting can be stopped?

Hi everyone, i continued my "hard bronze" project, my goal being, as a bladesmith, to make knives from something i can cast myself, forge and heat treat. Yes a bronze will never remotely reach the wear/hardness properties of even a cheap carbon steel, but keep in mind that's mostly a project i do for fun, and i want a mediocre but golden-looking knife. (and of course corrosion resistance isn't that important to me).

After having problems due to very stable dendrites from high cobalt additions to my previous prototypes, i tried adjusting the composition to inhibit the formation of those dendrites, however after a while i just realized that lowering the cobalt content was probably the best solution. (i wanted to add cobalt in the first place to improve wear resistance, following a US patent from 1958. Here i added a ratio of 0.09 cobalt per aluminium %).

My current alloy has the following composition : CuAl11Ni6.5Fe6Co1Mn1.5

Picture 1 and 2 :

Those are the alloy after forging and air cooling. The grains seem to be in a coarse pearlitic structure and are surrounded by a corrosion prone phase that etched black. The high nickel content should prevent the formation of gamma2, and most importantly, this alloy can be worked cold by a decent amount without cracking (around 30% reduction), compared to basically nothing on high aluminium bronzes that have a gamma2 phase present at room temp.

Could it be that the dark phase is retained beta ? Apparently cobalt is a beta-phase stabilizer. I wouldn't expect this grain boundary phase to be something brittle because of the reasonably high ductility.

Picture 3 and 4 :

Same alloy after a 30 min soak at 900°C, so a bit below the kappa phase dissolution temperature according to this paper : https://www.researchgate.net/publication/281644067_INFLUENCE_OF_HEAT_TREATMENT_ON_THE_MICROSTRUCTURE_AND_MECHANICAL_PROPERTIES_OF_ALUMINIUM_BRONZE

So it pushes the beta phase transformation but keeps some grain stability. The sample was then water quenched. The structure appears quite even and homogenous, the white dots could be some kind of impurity (my polishing was rough on that one). There are a few darker spots here and there, but it looks martenitic overall. After snapping the sample, the grain appeared quite fine, but not silky smooth. An eutectoid steel like 1075 at 800°C would have this kind of grain size.

The ductility after quench is low but it's not completely brittle yet. So for a knife blade you can actually straighten it. The hardness barely increases however, wich can be expected following this paper : https://www.researchgate.net/publication/402701878_The_effect_of_heat_treatment_on_the_structure_and_hardness_of_CuAl10Ni5Fe4_nickel_aluminium_bronze

After 30min at 450°C, the hardness increased by a LOT and the ductility/toughness was gone.

This paper : https://www.tandfonline.com/doi/abs/10.1179/030716980803286423 shows that cobalt additions slows down the decomposition of the martensite, so i can expect a higher hardness after tempering/aging.

Indeed, i compared the hardness trough a scratch test (high-tech, i know) on a sample of commercially-bought and similarly heat treated C63000 sample. My prototype alloy scratched it rather easily.

However the second study i linked reported a max hardness of around 580 HV after a short aging time ?? I've never heared of this kind of hardness on a bronze (CuBe2 doesn't even go this high), and i never could replicate it with my factory made C63000 alloy. Could this be an error ? Have you heared of ultra high hardness bronzes of this kind? I guess we can also expect them to perform as well a a piece of glass.

The last photo is my crude arc furnace that i use for making samples and upgrading the composition after a quick polish and low-quality microscope examination. Yes it's low tech (carbon crucible, carbon electrodes, ceramic insulation, charcoal dust to reduce oxygen exposure). No i don't have access to higher tech equipment to make/test my sample, so i can't know the exact hardness for exemple, i'll see if a friend has a HRC tester.

I guess a normalizing at high temp (950°C), and air cooling/quenching before the hardening heat treatment could reditribute a bit better the kappa precipitates and lead to a finer grain ?

Once again this is more of a fun side project so don't take it too seriously. I'm curious to know if you got suggestions !

Have a nice day y'all !

This car top carrier is probably 25-30 years old and still gets use. It is a Road Rider brand KarRite model. Mysteriously, only 1 of the 4 brackets is rusted, and I can’t understand why that would be. The whole thing has definitely seen rain, and all 4 corner straps have a steel toothed ladder lock to hold the straps in place, and all of those have a nice rust patina, where it’s discolored but I’m not really worried about the integrity of it. So why would 3 out of 4 of the steel brackets look pristine still and one of them have rust all over it and the bolts that hold it (also not enough to make me concerned about the integrity of it, but still…)?

Irrelevant info - New to the group and a bit of a metallurgist myself, in the sense that I studies MSE in college then barely used it for 10 years, and now non-ferrous metallurgy is a part of my daily job for the last 2. This one has me stumped, looking forward to what the experts might say, thanks.

This is about how the pig iron is made, but in the video I see completely different processes and 'torpedo cars' which look like tank cars transporting liquid hydrocarbons rather than liquid iron. And other processes also look unrealistic.

https://www.youtube.com/watch?v=o7Bzr5CKwwc

Brand new unsused fork, does this look like a hairline crack? If unsure any ideas of how to tell if it is/repair it?

Thank you

Hi, I have played around with copper and aluminum as a hobby and enjoyed creating a simple gold(ish) alloy from the two, mostly with jobsite copper wire scraps and melted aluminum cans for fun. I have since thought about separating the two through leaching and then an electrolysis bath but most of what I have read (while informative) vague on the actual process. I was hoping someone might have first hand experience or a more detail walk through on the process. I would like to be able to separate both effectively though if need be I would prefer to save the copper if only one is realistically salvagable using at home, non industrial capabilities.

The photo is for fun because I thought it turned out kind of cool when I made it with zero experience and simply messing around 😂

Yesterday, I was trying to improve the visualization of the microstructure of my Cu-Mn-Sn alloy (Lupine Bronze) in the unetched condition using liver of sulfur.

Iron is ferromagnetic and by heating you distort the arrangement of electron spins that make it magnetic, and it regains magnetism upon cooling.

I found this metal-like object at the beach today in Bodrum, Türkiye. It was a rocky beach, and I found it mixed in with the gravel/rocks. It’s not particularly heavy, but it feels somewhat heavy for its size. I’m wondering what it could be. Any ideas?