Titanium Alloy Composition for Grain-Refined Additive Manufacturing
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Solution Overview
Problem
Conventional additive manufacturing techniques for titanium alloys result in coarse as-solidified grain structures with elongated shapes, leading to reduced mechanical properties and anisotropic behavior due to lack of mechanical forming and directional heat extraction.
Innovation Solution
The use of aluminum- and molybdenum-based titanium alloys with small additions of bismuth (Bi) promotes significant grain refinement, achieving isotropic high-strength mechanical properties and equiaxed prior-β grains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional additive manufacturing techniques are used for titanium alloys, then near-net-shape components can be produced with complex shapes, but coarse as-solidified grain structures with elongated shapes result, leading to reduced mechanical properties and anisotropic behavior
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the titanium alloy, specifically adding beryllium (0.001-0.05 wt%), hafnium (0.01-0.1 wt%), and zirconium (0.1-1.0 wt%). These compositional parameter changes fundamentally alter the solidification behavior to produce equiaxed grains instead of elongated columnar grains, thereby improving mechanical properties while maintaining the additive manufacturing process capability for complex shapes
2Adaptability or versatility
If conventional additive manufacturing techniques are used for titanium alloys, then near-net-shape components can be produced with complex shapes, but coarse as-solidified grain structures result, leading to anisotropic behavior
Solution Approach 1:
The patent changes the alloy composition parameters by introducing specific elements (beryllium, hafnium, zirconium) that modify the solidification characteristics. These parameter changes promote equiaxed grain formation during additive manufacturing, which eliminates the directional dependence (anisotropy) inherent in conventional processes, thereby achieving isotropic mechanical properties while maintaining the ability to produce complex shapes
3Strength
If intermediate forming steps are applied to achieve recrystallized grain structure, then mechanical properties are improved, but effective deposition rate is reduced and freedom of fabrication is limited
Solution Approach 1:
The patent applies preliminary action by pre-modifying the alloy composition with specific elements (beryllium, hafnium, zirconium) before the additive manufacturing process. This preliminary compositional adjustment ensures that the material inherently forms equiaxed grains during solidification, eliminating the need for subsequent intermediate forming steps. Consequently, both productivity (deposition rate) and fabrication freedom are maintained while achieving improved mechanical properties
4Strength
If intermediate forming steps are applied to achieve recrystallized grain structure, then mechanical properties are improved, but processing time is added and productivity is reduced
Solution Approach 1:
The patent implements preliminary action by incorporating grain-refining elements (beryllium, hafnium, zirconium) into the alloy composition before manufacturing. This preliminary compositional design enables the material to self-form equiaxed grains during the additive manufacturing solidification process, eliminating the need for time-consuming post-processing forming steps. The result is reduced total processing time while maintaining improved mechanical properties
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 addition of bismuth to titanium alloys in additive manufacturing processes results in refined solidification structures with reduced average grain size, improved strength, fatigue resistance, and isotropic properties, comparable to mechanically worked titanium alloys.
Implementation Method 1
The addition of bismuth to titanium alloys in additive manufacturing processes results in refined solidification structures with reduced average grain size
Implementation Method 2
molten material is added in layers, solidifies and cools down without any mechanical forming
Data Source
AI summary
The present invention relates to titanium alloy compositions suited for manufacturing components by additive manufacturing, resulting in components that exhibit relatively small prior β-grain sizes. The titanium alloy compositions comprises: from 2 to 7 wt % Al, from 1.5 to 6 wt % Mo, from 0.25 to 1.5 wt % Bi, unavoidable impurities, and a remaining wt % Ti which makes the total content of constituents in the titanium alloy composition sum up to 100 wt %, wherein the weight percentages are based on the total mass of the titanium alloy composition.