I have aquired some lengths of nitinol wire that I am attempting to “train.” It is 0.009" diameter, 56% Nickel: 44% Titanium. Straight annealed temper. Natural Oxide finish. According to the manufacturers instructions, it simply needs to be restrained in the shape you wish it to hold, and heated above 500C for at least 5 minutes. I have fabricated a jig out of aluminum plate with a series of pins to hold the wire in the proper position (a clover with each “leaf” having a roughly 1/2" diameter.) I have been putting the jig in a kiln heated to the proper temeprature. I let the jig and the wire soak for about 10 minutes, then pull it out and allow it to cool. On removal from the jig however, the wire does NOT conform to the shape of the jig, and heating it has no further effect. Any ideas? Do I need to heat it longer, or quench it instead of letting it air cool? Any and all help is appreciated.
I wonder if your metal jig is acting as a heatsink and preventing the wire from reaching the desired temperature for the desired duration.
Thats a thought. I’ve just turned the kiln on again and I’ll try to let the jig soak longer. The problem with that is the kiln is controlled by a 1980’s vintage industrial process controller and the last person who knew how to program it retired long ago. The only way to keep it at a resonably constant temperature is to manualy turn it off and on. Kind of a pain in the ass, but I’ll try anyway.