| 摘要 |
This disclosure relates to shape memory alloys which have been subjected to a thermal and mechanical treatment to increase the austenite start temperature A s .fwdarw. A s' such that the shape memory alloy is martensitic at body temperature and when subsequently subjected to a controlled deformation, the shape memory alloy preferentially reverts to the parent phase. One application for this disclosure is a stent for use in a lumen in a human or animal body having a generally tubular body formed from a shape memory alloy which has been subjected to a thermal and mechanical treatment so it deforms as martensite until a critical expansion diameter is reached at which point the tubular body rapidly reverts to the parent phase with much higher mechanical properties. The shape memory alloy comprises Ni-Ti and a ternary element ranging from about 3 at.% to about 20 at.%. The ternary element is effectively insoluble in a Ni-Ti matrix. In a preferred embodiment, the element is selected from the group consisting of niobium, tantalum and zirconium.
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