| 摘要 |
This invention relates to shape memory alloys which have been subjected to a thermal and mechanical treatment to increase the austenite start temperature A<SUB>s</SUB> ? A<SUB>s'</SUB> 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 invention 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 nickel, titanium and from 3 at. % to about 20 at. % of a ternary element. The ternary element is insoluble in a Ni-Ti matrix, hi a preferred embodiment, the element is selected from the group consisting of niobium and tantalum. |
