What quenching and tempering does to SWORDS

Trigger warning: Aussie accent...keep hacky comedians and actors away lest they start doing the Philosophers song.

There's a whole bunch of high-quality explanation in this one...

• 1:19 - percentage breakdown of carbon in various steels (low carbon, medium carbon, high carbon)
• 1:49 - "When the iron is hot...reaches the austenite phase...lost magnetic interaction...body centered cubic or face centered..." Honestly, he screws up the crystals verbally (though the graphics are correct) but does nicely say that "there's more room in between the iron atoms when it's this hot which means carbon atoms can all fit around evenly wherever they want" and that "when iron is cool...they try and squeeze out the carbon in between these iron atoms" and shows ferrite in the graphic
• 2:56 - micrograph of ferrite and cementite as the carbon in squeezed out from between the iron atoms, making pearlite
• 4:16 - Say "crystals" not "structure", man...c'mon
• 4:44 - discussion of work hardening and how that's lost once the metal is reheated, "it loosens the insides. It basically gives the opportunity for the stresses to be released and moved around and become uniform...as soon as you heat it up, you're losing whatever benefits - but also detriments - you might've put into the steel"
• 8:16 - "When heated up to where austenite is formed in the steel, the carbon is not forced into these veins/pocket/lines...and if you were to cool it down rapidly, you can actually give those iron atoms not enough time to force [carbon] out into these more condensed pockets...and a different, amazing crystalline structure is formed within the steel called martensite"
• 9:40 - "[Martensite] can be very useful to swords because you want swords to have a very hard edge, but you don't want them to be too brittle"...Goldilocks of metals, eh
• 10:05 - how the Japanese solved the problem, great diagram of the anatomy of a samurai sword (ion core, pearlite jacket, martensite edge) created via clay control of cooling rate
• 11:50 - tempering makes its appearance...we've been waiting, Shad
• 12:30 - showing quench of a katana with differential cooling causing bending in both directions (flubbed vocals but corrected captions)
• 13:10 - "[tempering] releases stress between these dislocations creating a much greater level of ductility and flex in between the crystal structure that's being formed within it" - nice micrographs of martensite and tempered martensite
• 15:00 onward...what makes for a good sword, particularly its sharpness...not so much material science