“Nitinol: a shape memory alloy” experiment

Why it takes its initial shape

Can you re­mem­ber what you did last Tues­day? This al­loy can even re­mem­ber its shape af­ter 10 years!

Safe­ty pre­cau­tions

Ob­serve safe­ty rules when work­ing with flame and heat­ed ob­jects.

Warn­ing! Don’t try to re­peat this ex­per­i­ment with­out a pro­fes­sion­al su­per­vi­sion!

Reagents and equip­ment:

  • niti­nol (clip, spring);
  • lighter;
  • plum­met;
  • hot wa­ter;
  • Petri dish;
  • heat­ing de­vice (hot­plate).

Step-by-step in­struc­tions

Take a niti­nol clip or spring and bend it. Now heat the de­formed item with a lighter, hot wa­ter and heat­ing de­vice. The clip and spring take their orig­i­nal shape!

Pro­cess­es de­scrip­tion

Niti­nol is an al­loy which is 55% nick­el and 45% ti­ta­ni­um. This al­loy is in­ter­est­ing be­cause it can re­mem­ber its shape. When a niti­nol item is heat­ed, the atoms in it “re­mem­ber” their po­si­tion, and so on re­peat­ed heat­ing they try to take this po­si­tion. If a niti­nol item is de­formed and then heat­ed, the atoms take their ini­tial po­si­tion, and the shape of the item is re­stored.