NiTiHf Superelastic Medical Components for Additive Manufacturing Strength
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Solution Overview
Problem
Additive Manufacturing (AM) techniques for NiTi alloys, such as laser sintering, result in materials with low resistance to conventional deformation, compromising superelastic properties due to limitations in solid solution strengthening and aging mechanisms.
Innovation Solution
A near-net shape additive manufacturing method using a pre-alloyed metallic powder containing Nickel, Titanium, and Hafnium, with a Hafnium atomic percentage between 4-10%, applying pulsed laser energy to fuse layers and subsequent aging to achieve high Ultimate Tensile Strength (UTS) and reduced residual set.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If additive manufacturing techniques (laser sintering) are used to fabricate NiTi alloy devices, then complex three-dimensional shapes can be achieved, but the resulting material has low resistance to conventional deformation
Solution Approach 1:
The patent changes the chemical composition parameters of the NiTi alloy by adding specific amounts of third elements (Al: 0.1-1.0 at%, Fe: 0.1-1.0 at%, Cu: 0.1-1.0 at%, or Zn: 0.1-1.0 at%) to enable solid solution strengthening in additively manufactured devices, thereby improving strength without sacrificing the AM manufacturing capability
Solution Approach 2:
The patent creates a composite alloy system by combining NiTi base alloy with third elements (Al, Fe, Cu, or Zn) that provide strengthening mechanisms, effectively creating a multi-component alloy that maintains superelasticity while adding resistance to conventional deformation through solid solution strengthening
2Strength
If cold working is used to harden conventional NiTinol, then strength increases, but this mechanism is not available to devices made through additive manufacturing since the very idea of AM is to produce the net shape
Solution Approach 1:
The patent applies preliminary action by incorporating strengthening elements (Al, Fe, Cu, Zn) into the alloy composition before additive manufacturing, so that the strengthening mechanism is built into the material itself during fabrication, eliminating the need for post-manufacturing cold working steps
Solution Approach 2:
The patent changes the material composition parameters by adding third elements that enable solid solution strengthening, replacing the need for cold working with a compositional approach that is compatible with additive manufacturing's net shape capability
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 produces AM components with UTS of at least 900 MPa and less than 2% residual set after 6% tensile deformation, suitable for medical devices that can be implanted in the body, enhancing their superelastic properties and resistance to conventional deformation.
Implementation Method 1
applying a suitable energy to a first quantity of a pre-alloyed metallic powder material comprising Titanium, Nickel and Hafnium on a substrate so as to fuse particles of the pre-alloyed powder material into a first layer on the substrate
Implementation Method 2
The suitable energy source may be from one or a combination of laser sintering, selective laser sintering, directed light fabrication, laser engineered net shaping, and direct laser powder deposition
Implementation Method 3
The fabricated near net shape implantable medical device can be subsequently aged such that the Af temperature is less than body temperature and the UTS is at least 900 MPa
Data Source
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AI summary
A near net shape medical device is described that is formed from a metal alloy mixture containing NiTiHf using additive manufacturing techniques. The medical device is aged to a desired ultimate tensile strength (UTS), presence of H-phase precipitate with an Af below body temperature.