Alloys

Useful information
Kit List: 

Cutlery, cheap stainless set more expensive stainless set (all spoons)
Magnet
NiTinol springs
NiTinol Magic Tricks (Bending Paperclip and Heart Wire)
Normal steel spring
Heat gun and tongs
Other lumps of metal could be good needs more thought
(Double check RA) Sandy Plasticine Models (increments of 2g sand to 35g Plasticine)

Packing Away: 

This experiment now lives in the new small blue box called 'Periodic Table, Alloys and Carbon Allotropes', all three experiments may be done in combination. It's contained in a small Tupperware and a pencil case.
Plasticine should be sealed in air tight pots!
This experiment used to live in Misc box.

Frequency of use: 
1
Explanation
Explanation: 

What is an alloy? A metal which is a metal mixed with something. More rigorously: A metallic solid or liquid that is composed of a mixture of two or more metals, or of metals and nonmetal or metalloid elements, usually for the purpose of imparting or increasing specific characteristics or properties.

Alloys may be homogenous or inhomogenous depending on how the different metals interact. This will have a large effect on the properties of the alloy, so alloying additions need to be carefully chosen to ensure you optimise the properties and don't ruin the stock.

The composition and manufacturing conditions of the alloy will determine which phases are present in the metal. A phase is the specific arrangement of atoms in the unit cell of a crystal lattice. For example in steels, the austenite phase is a face-centred cubic arrangement of iron atoms while the ferrite phase (typically more stable at room temperature) is body-centred cubic.

Say that you can tell how expensive someone's cutlery is from whether it is magnetic. Good stainless steel contains Cr and Ni, the Ni stabilizes austenite phase which is not magnetic. Bad stainless steel contains just Cr, this means the ferrite (magnetic) phase is stable and therefore cheap cutlery is magnetic. The proportions are usually 18:10, 18:8 or 18:0 Cr:Ni - the higher the Ni content the higher the quality. Show that the good John Lewis stainless steel is non-magnetic and the cheap Asda stainless steel is magnetic. The result of this means the Asda cutlery scratches more easily, which makes it look less shiny.

(Look at other properties. Ask if they know the difference between hardness and toughness? Most won't, toughness is a measure of the amount of impact energy it can take before fracturing, whereas hardness is a measure of its how difficult it is to scratch. This is related to strength, which is a measure of how hard it is to permanently plastically deform.)

Finally, demonstrate the shape memory alloys. Ask members of the audience to deform the NiTinol wire sample. After this, tell them you will return it to its original shape. Heat up using the heat gun, holding the wire using a pair of tongs. If the wire has been tangled by an ambitious member of the audience, you may need to untangle it, as this may prevent the wire from uncoiling fully. The ideal geometry is to curl the wire into a spring.

-------Plasticine Models -------------
I have made some Plasticine alloy models which you can play around with (once RA checked). They're made by taking Plasticine (duh) and varying quantities of sand. Please pack them away in the nice sealed containers so they don't dry out! Get kids to play with some they're body temperature and then roll them into a cylinder (approx 1.5cm diameter x 6cm length, although having the different alloys similar size is more important) then gently pull apart till you get a gentle failure (no arms flying around, that's not gentle). You should get a ductile fracture, small pockets form, these coalesce, then a crack propagates until we reach separation. Compare the forces needed, the fracture surfaces (using a magnifying glass, you could even compare to a tear or snap you make) and make theories about what adding the sand has done.

Risk Assessment
Date risk assesment last checked: 
Sat, 11/01/2020
Risk assesment checked by: 
Emma Crickmore
Date risk assesment double checked: 
Mon, 20/01/2020
Risk assesment double-checked by: 
Beatrix Huissoon
Risk Assessment: 
Hazard Affected Person(s) Risk Likelihood Severity Overall Mitigation Likelihood Severity Overall
Heat gun All Fire risk and also the possibility of burns. 3 3 9 Demonstrator to control heat gun. Do not leave on. Keep flammable material away from the heat gun. Use stand instead of lying heat gun on a surface. Do not touch the heat gun.
In case of burns, run affected area under cold tap for 10 minutes. Call a first aider. Follow venue RA protocols in case of fire.
2 3 6
NiTinol wire and tongs hot when heated All Risk of burns. 3 3 9 Do not let anyone near the heated wire. The wire is thin and should cool within a few seconds, but care should be taken with the tongs. If possible, obtain a heat-resistant mat to lay the tongs/wire on after heating.
In case of burns, run affected area under cold tap for 10 minutes. Call a first aider. Follow venue RA protocols in case of fire.
2 3 6
Ends of wires All Cuts 4 2 6 Make sure sharp ends are doubled back 3 2 6
Cutlery All Stabbing self/others 4 3 12 Don't use any sharp knives or forks. 4 1 4
Magnets Public Skin getting caught between cutlery and magnet 3 3 9 Use weak magnet so won’t cause harm if occurs 3 1 3
Plasticine Models Public Make sure children don't eat models. Make sure breaking is gentle so don't 'accidentally' punch near by children when arms fly apart. 3 2 6 Plasticine and sand are both non-toxic, although parents should be informed as eating small quantities may lead to stomach upset. Large quantities may require a stomach pump however there's no need to be giving out large amounts. Don't give plasticine to small children. Ensure children are stood apart while testing models and ensure they gently pull. 1 1 1
This experiment contains mains electrical parts, see separate risk assessment.
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