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Shape memory articles and methods of controlling properties

A technology of memory alloy and fatigue performance, which is applied in the direction of medical formula, human tubular structure devices, blood vessels, etc., can solve the problems of plastic instability and nucleation difficulties, and achieve good sealing, enhanced device performance, easy function and durability. Effect

Pending Publication Date: 2019-12-17
MEDTRONIC INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Therefore, it is postulated that it is more difficult to nucleate microcracks or plastic instabilities that could lead to fatigue fracture in produced articles made from stronger hyperelastic SMA materials

Method used

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  • Shape memory articles and methods of controlling properties
  • Shape memory articles and methods of controlling properties
  • Shape memory articles and methods of controlling properties

Examples

Experimental program
Comparison scheme
Effect test

Embodiment approach 1

[0219] In this embodiment, the components or subassemblies are first shaped into their final geometry. A final heat treatment or series of multiple heat treatments is then performed while the (sub)assembly is in a relaxed state (ie, no deformation or load is applied to the target area). Zero stress / strain heat treatment can be performed either completely off the mandrel or using a holding or support fixture that does not impose additional stress or strain on the component at heat treatment temperatures.

[0220] Embodiment 1a - Low Temperature Zero Stress / Strain Conditioning

[0221] Time = 15 seconds - 600 seconds

[0222] ·Temperature = 300°C–525°C

[0223] ・Stress / strain = 0

[0224] Zero stress / strain conditioning at low temperature promotes the separation of R′ and austenite phases, as assessed by DSC. This separation results in high flexural stiffness with low upper and lower platform stress values. In some embodiments, the separation of the R' phase and the austeni...

Embodiment approach 2

[0235] The nucleation barrier for the formation of Ni-rich precipitates in austenite is high, heterogeneous nucleation at grain boundaries during heat treatment of components and subassemblies under relaxed conditions (i.e. in the absence of externally applied loads) It is energetically favorable. Stress-assisted aging (aging under deviatoric stress / strain) can effectively produce uniformly distributed precipitates in slightly nickel-rich near-equiatomic Ni-Ti SMA. Thus, in this embodiment, the assembly or subassembly experiences non-zero stress / strain during the final heat treatment step. This non-zero stress / strain heat treatment is achieved by deforming the (sub)assembly using a mandrel or other constraining fixture.

[0236] Embodiment 2a - Low Temperature Non-Zero Stress / Strain Conditioning

[0237] Time = 15 seconds - 600 seconds

[0238] ·Temperature = 300°C–525°C

[0239] Stress / strain = non-zero

[0240] Non-zero stress / strain conditioning at low temperature prom...

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Abstract

Method for controlling the properties of a structural element of an implantable medical device, wherein the structural element comprises a shape memory alloy (SMA), the method comprising promoting or inhibiting the in vivo formation of an R-phase crystalline structure, or combining the R-phase with the austenitic phase Merge or separate.

Description

[0001] related application [0002] This application claims the benefit of U.S. Provisional Application No. 62 / 491,423, filed April 28, 2017, and U.S. Provisional Patent Application No. 62 / 529,121, filed July 6, 2017, each of which is incorporated by reference in its entirety incorporated into this article. technical field [0003] The present disclosure relates to articles, such as implantable medical devices or components thereof, formed from superelastic or pseudoelastic shape memory alloys, such as nitinol shape memory alloys. Background technique [0004] Certain alloy compositions, such as the nearly equiatomic alloy of nickel and titanium (Nitinol), exhibit two atypical behaviors when properly processed: the shape memory effect (SME); and pseudoelasticity. The shape memory effect describes the ability of an article made of a shape memory alloy (SMA) to return to its original shape and configuration when heated, for example after being deformed at a sufficiently low t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C1/02A61L27/06A61L31/02A61L31/14A61F2/06A61F2/94C22C14/00C22C19/03C22F1/00C22F1/10
CPCA61F2210/0019A61L27/06A61F2/91C22C1/02C22C14/00C22C19/03C22F1/006C21D2201/01A61L27/50A61L2400/16A61F2/2418C22F1/10A61L2430/20A61F2210/0014A61F2240/001A61L27/047A61F2/86
Inventor R·弗朗西斯B·福格C·格罕福斯S·罗伯特森D·卡图
Owner MEDTRONIC INC
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