Steel Metallurgy - Principles of Metallurgy

Again with the mAtallurgy Data channel...

Maybe they're trying to combine material and metallurgy into matallurgy?

Whatever portmanteau they're aiming for, their videos are excellent for understanding metals. This one goes over how different metallic ingredients affect the properties of alloy steels, the carbon-iron phase diagram, CTT and TTT graphs (something I haven't seen before, admittedly), hardenability, and ways to strengthen steel.

It's not necessarily written for my students' levels - most of them, anyway - but it's good background understanding for me to have.

Properties and Grain Structure

Properties and Grain Structure: BBC 1973 Engineering Craft Studies

Yup, 1973...that means not only is the narration done with an English accent, it's also paced for a 1973 world meaning I ran the video at 1.5 speed to bring it up to a modern pacing.

The video shows the etching process for various metals then does it again after cold rolling the aluminum sample, then discussing how the material's properties (ductility, hardness, toughness) change.

The video then repeats things for heat treating after cold working the aluminium (sp?)...then various carbon steels being annealed, quenched, and tempered.

I absolutely love the hand-cranked tensile tester that we see at around 8:10 in the video.

It's a great video for showing the properties and crystal structures of aluminum (sp?) and steel and how the crystal structures coordinate to that.

Why copper pans are great (and sometimes poisonous)

I can vouch for that Harold McGee book referenced toward the beginning. I have it on the shelf in my living room - though I'll admit that I've barely read more than a third of it. There's a LOT of science happening in there, and it's a dense read.

Adam explains the basics of heat conductivity, reactivity (leaching ions to make whipping egg whites easier), reactivity again (to pull sulfur out of the vapor distillate in alcohol distillation), malleability (peening the copper bowl), ductility (making copper whisks), reactivity another time (such as the health hazards of drinking acidic cocktails like mules from copper cups), and conductivity again (useful for making jams and candy).

And then he throws down the possibility of testing a pure silver pan...I want him to buy one, but I'm not going to support him to make that easier for him to do.

Material Properties 101

The narrator's Irish accent, tho...

The introduction to the video says there are six terms that he's hoping we understand by the end of the video...

• stiff
• strong
• ductile
• brittle
• tough
• hard

Man, if all of my students understood those terms by the end of the semester, I'd be thrilled.

We get coverage of a tensile test to explain stress, strain, and the stress-strain curve (along with many of its aspects - yield strength, ultimate strength, Young's modulus, fracture, tensile strength, max allowable load/stress, toughness).

He then covers hardness briefly, explaining how the Rockwell hardness test works.

It's not perfect because it left me wanting to know more...but maybe that's the point.

The entire video is six minutes long, and the last forty-five seconds or so is an advertisement for the video's sponsor - annoying but still school appropriate, thankfully.

Tensile test

Computer modeling is so cool.

Like in this tensile test, you can see that the force concentrates as the cross sectional area of the sample decreases, leading to more and more drastic necking.

I can't see that when I look at a real sample being tested, but with the rainbow coloration for the different amounts of force, I can kind of show that to my students.

Misconceptions about heat

In today's video Dr Derek Muller of Veritasium takes a few minutes to again tell people that they're wrong. He seems to do that a lot. I'm not saying, but I'm just saying...

The informality of the testing that he does is one of Muller's great advantages since it leaves the viewer fairly well able to reproduce many of the experiments that he does. Yeah, he uses an infrared thermometer here, but that's not radically out of the realm of expenses for most folks.

The testing today is looking at whether a book - apparently an Asimov tome - is warmer or cooler than an aluminum-cased hard drive. The trick is that they're both at room temperature...the same temperature. It's just that the two materials transfer heat very differently.

There's a similar video with slightly higher production value also by Dr Muller over on the Catalyst, an ABC Australia program, website. The video there is downloadable but not embeddable, and it does have a nice transcript of the prettier video. They also have a larger version of the downloadable video, but it's not viewable in the US. It does, however, come with some teacher material.

Strength - Toughness

Strength and toughness are two properties that, as the terms are used in the non-scientific world.

Something that is strong must also be tough. They mean the same, right?

To a materials scientist, they most certainly do not. As the linked website defines, 'strength measures the resistance of a material to failure, given the applied stress (or load per unit area)' and 'toughness measures the energy required to crack a material; it is important for things which suffer impact.'

The interactive diagram (called Ashby diagrams) on the linked website graphs the strength vs toughness for a number of materials and finds them grouped with like materials (wood near wood, polymers near polymers, etc). The graph also has some java-based interactivity allowing each group to be further explored.

The site has a number of links at the bottom to similar pages exploring other materials relationships: young's modulus vs cost, strength vs cost, and a dozen more.

PS - Thanks to Todd for finding this site and to Caryn for passing it along.