I am looking for a non-toxic material for a wire/rod that allows room temperature deformations without work hardening.

Example uses are semi-rigid cables that one can bend and that hold their shape afterwards or snake-like cellphone holders like the one in the image below.

I looked at a very old one I had lying around and found it was simply a lead rod. (Or at least is looked and felt like a lead rod.) To me using lead did make sense since its recristallisation temperature is lower than room temperature - hence no/very little work hardening.

Are there any alternatives that are at the very least non-toxic or even better bio-compatible? I looked at electronics solder since their melting point is fairly low but found they do exhibit work hardening at room temperature and break after multiple deformations.

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2 Answers 2


A few that I worked on used an aluminum rod. And yes it did work harden. And yes lead would be a poor choice from a safety and environmental standpoint. Aluminum is probably the most economical, but copper and annealed steel could also be evaluated.

The main way the work hardening is limited in the designs I have seen is a polymer sheath is installed around the outside to limit the minimum radius such that the number of fatigue cycles to failure are greater than the required life of the device. For a cell phone holder, probably 100 cycles would be sufficient.

Another way to reduce work hardening for a given radius is to use multistrand wire, however it will not hold its position as well or as much load.

There are also some low temperature formable polymers that may work well for your application, but require heating and cooling in order to reposition rather than just force.


I'm curious what material they currently use in these cellphone holders?

The recrystallisation temperature of tin is about 30C, so conceivably it could work as a non-toxic alternative in lieu of lead.

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    $\begingroup$ Annealed tin makes a sound when deformed . but not a second time ,so there is some change. Many flexible rods use movable mechanisms , not deformable materials. $\endgroup$ Jun 15, 2020 at 15:23

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