Perfect superelasticity by dispersion of effective precipitate routed through brittle phase in biomedical titanium alloy

β-钛超弹性合金是一种具有潜在应用前景的医用超弹性合金，但目前还没有有效的组织控制方法来抑制与超弹性变形竞争的滑移变形。因此，β-钛合金的超弹性变形不是理想的，变形后仍存在塑性应变。提出了一种新的热处理方法，即在细小的ω相处形核析出细小的α相，以达到强化的目的。ω相具有极强的脆性，在钛合金的常规热处理中不被使用，而在我们的新方法中，它被用作ω相形核的介质。Ti-Mo-X（X=Al和Mn）合金经773 K（细ω析出）→ 1023 K（ω处细α析出）→ 1123 K（消除ω）三步热处理后，强度可达800 MPa，形状回复良好。此外，作为第四步的约373 K的低温热处理改善了机械性能。

There is no effective method of microstructural control to suppress the slip deformation that competes with superelastic deformation inβ-Titanium superelastic alloy, though this alloy is a candidate biomedical superelastic alloy. The superelastic deformation in β-titanium alloy is, therefore, not a perfect one ; plastic strain remains after deformation. We propose a new heat-treatment method to precipitate fine α-phase for strengthening that is nucleated at fine ω-phase. The ω-phase brings extreme brittleness and is not used in usual heat-treatment of titanium alloy, whereas it is used as a medium for ω-phase nucleation in our new method. 800MPa in strength and perfect shape recovery are achieved by a three-step heat-treatment : 773K (fine ω precipitation)→1023K (fine α precipitation at ω)→1123K(erasing ω) in Ti-Mo-X (X=Al and Mn). In addition, a low-temperature heat-treatment around 373K as the fourth step improved mechanical property.