| 摘要 |
A method of treating an element made of "ferro-elastic" material for use in or as a thermally actuated device comprises heating the element to above its "transition point", forming the element into a desired operative shape, allowing it to cool to below the transition point and forcing the element into a non-operative shape. "Ferro-elastic" materials are defined as materials which exhibit substantial mechanical strength above a certain temperature (the "transition point"). Below this temperature they are mechanically weak and can be readily shaped. An example of the material is cadmium 47.5 per cent (atomic weight) and up to 52 per cent gold, which has a transition point of about 60 DEG C. For use in the human body the transition point can be lowered by the addition of copper and/or silver. An addition of 0.5 per cent copper is stated to lower the transition point to the region of 39-42 DEG C. The alloy is preferably monocrystalline, but poly-crystalline alloy may be used, prepared by placing the alloy in powder form in a glass tube, heating the tube until the material melts and the tube softens, and pulling the tube until it constitutes a capillary which is then cooled before the alloy is removed. |
