NiTi Medical Components R-Phase Stabilization
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Solution Overview
Problem
Conventional NiTi alloys used in medical devices exhibit limitations in superelastic properties and performance characteristics, particularly in maintaining stability and functionality at body temperature, with existing designs relying on Austenite to Martensite transformations that do not effectively utilize the R-phase for improved durability and compatibility.
Innovation Solution
A method of processing TiNi materials to produce medical components with stress-free M*s below normal body temperature, incorporating R-phase stabilization through cold or warm working, aging under stress, and further aging below 300°C to achieve desired R-phase characteristics, allowing for stress-induced R-phase formation and reversible transformations between R-phase and Martensite, thereby enhancing durability and compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional NiTi alloys are used with Austenite to Martensite transformations, then superelastic properties are achieved, but durability and physiological compatibility at body temperature are limited
Solution Approach 1:
The patent modifies the transformation temperature parameters of NiTi alloys by controlling the stress-free Ms below body temperature through composition adjustment and heat treatment, enabling the material to exhibit R-phase characteristics at physiological temperatures. This parameter change allows the material to maintain superelasticity while improving durability and biocompatibility through reduced hysteresis and residual deformation.
Solution Approach 2:
The patent creates a composite phase structure within the NiTi alloy, combining R-phase and Martensite phases in a critical region. This internal composite structure allows the material to leverage the low-hysteresis properties of R-phase while maintaining the high strength and transformability of Martensite, thereby simultaneously improving durability and physiological compatibility.
2Reliability
If R-phase stabilization is implemented through cold or warm working and aging treatment, then hysteresis is reduced and fatigue resistance increases, but manufacturing process complexity increases
Solution Approach 1:
The patent applies cold or warm working and aging treatment during the manufacturing process to pre-stabilize the R-phase structure before the component is deployed. This preliminary action ensures that the material achieves the desired low-hysteresis, high-fatigue-resistance properties in advance, eliminating the need for additional post-installation treatments or adjustments.
Solution Approach 2:
The patent utilizes controlled phase transitions during manufacturing—specifically, inducing and stabilizing the R-phase through cold/warm working followed by aging treatment at temperatures below 300°C. This phase transition approach allows the material to lock in a microstructure that inherently provides superior fatigue resistance and reduced hysteresis, with the complexity confined to the manufacturing stage rather than operation.
3Reliability
If stress-free Ms is lowered below body temperature, then R-phase characteristics are achieved in-vivo, but control over transformation temperatures becomes more difficult
Solution Approach 1:
The patent systematically adjusts multiple parameters including nickel content (50.5-51.5 at%), cold working temperature and degree, and aging treatment conditions to precisely control the stress-free Ms below body temperature. By coordinating changes across these parameters, the patent achieves stable R-phase characteristics while maintaining manufacturability and transformation temperature control.
Solution Approach 2:
The patent employs feedback control during the manufacturing process, where transformation temperatures are measured and monitored, and subsequent processing steps (cold working, aging) are adjusted based on these measurements to achieve the target stress-free Ms below body temperature. This feedback approach ensures precise control over transformation temperatures while achieving reliable R-phase stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in medical components with improved durability and physiological compatibility, as evidenced by reduced hysteresis and increased fatigue resistance, with the R-phase stabilization allowing for greater strain accommodation and reduced residual deformation, leading to enhanced performance in medical applications.
Implementation Method 1
reversible transformations between R-phase and Martensite
Implementation Method 2
superelastic properties
Implementation Method 3
R-phase stabilization allowing for greater strain accommodation
Implementation Method 4
aging under stress, and further aging below 300°C
Implementation Method 5
cold or warm working
Data Source
AI summary
There are super elastic NiTi materials for use as medical components, especially implantable medical components, and methods of fabricating such components to have desired R-phase characteristics in-vivo. Additionally, there are methods of processing a TiNi material to produce an implantable medical component by cold or warm working the TiNi material at least 15%; aging the cold or warm worked TiNi material under stress at between 300-700° C.; and further aging the TiNi material below 300° C. to produce desired R-phase characteristics. Additionally, there are methods of processing a TiNi material to produce a medical component by processing the TiNi material to produce a medical component that has a stress free M*s below a normal body temperature. Additionally, a TiNi material is used to produce a super elastic medical component from a tube, a sheet, a wire or a strip to have a stress free M*s below a normal body temperature.