Multi-scale Iron Alloy Oxide Dispersion
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Solution Overview
Problem
Existing methods for preparing oxide dispersion strengthened (ODS) iron-based alloys face challenges in achieving homogeneous distribution of nano-scaled oxides, leading to poor mechanical properties due to inhomogeneous dispersion and coarse oxide particles, which reduces the alloy's high-temperature mechanical properties and oxidation resistance.
Innovation Solution
A multi-scale and multi-phase dispersion strengthened iron-based alloy is developed through mechanical alloying of atomized Fe—Cr—W—Ti pre-alloyed powder with Y2O3, followed by hot extrusion, hot rolling, and heat treatment, utilizing a combination of milling balls with varying diameters to achieve nano-sized Y2O3 with high-density defects and amorphization, resulting in homogeneous distribution of multiple oxide phases within the alloy matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If mechanical alloying is used to disperse oxide particles into alloy matrix, then oxide particles can be distributed in alloy matrix, but the oxide particle size becomes coarse and distribution becomes inhomogeneous, which reduces mechanical properties
Solution Approach 1:
The patent segments the oxide dispersion process into multiple stages with different ball-to-powder ratios and milling parameters. Initial coarse milling distributes oxide particles, followed by fine milling with smaller balls to reduce particle size. This multi-stage segmentation approach prevents coarse particle formation while achieving homogeneous distribution.
Solution Approach 2:
The patent dynamically adjusts milling parameters including ball-to-powder ratio, milling speed, and atmosphere composition during different stages of mechanical alloying. The ball-to-powder ratio is changed from 10:1 to 20:1 between stages, and argon atmosphere is introduced to prevent oxidation during extended milling, enabling optimal particle size control.
2Stability of the object's composition
If mechanical alloying is performed for long time to decompose Y2O3 into atoms, then solid solution can be formed, but Y2O3 decomposition is difficult and large-sized oxide with inhomogeneous distribution is formed instead
Solution Approach 1:
The patent changes physical parameters including extending milling time to 100-150 hours, reducing ball-to-powder ratio to 20:1, and controlling atmosphere composition with argon. These parameter changes enable progressive oxide particle size reduction from micrometer to nanometer scale without complete decomposition, achieving optimal dispersion.
Solution Approach 2:
The patent performs preliminary mechanical alloying to distribute oxide particles before attempting decomposition. The initial stages focus on homogeneous distribution, creating a precursor state that facilitates subsequent nanoscale particle formation without requiring complete oxide decomposition.
3Ease of manufacture
If conventional atomization and mechanical alloying process is used, then pre-alloyed powder can be prepared, but the process is complex and Y2O3 segregation occurs during forming
Solution Approach 1:
The patent merges the atomization and mechanical alloying steps into a single integrated process. Atomized powder containing alloying elements is directly subjected to mechanical alloying with oxide particles, eliminating the need for separate pre-alloying and oxide addition steps. This combination prevents Y2O3 segregation during forming.
Solution Approach 2:
The patent maintains continuous mechanical alloying action for extended periods (100-150 hours) without interruption. The continuous milling ensures progressive and uniform oxide particle size reduction and distribution, preventing segregation that would occur with intermittent processing.
4Quantity of substance
If chemical infiltration method is used to introduce Y2O3, then oxide can be introduced into alloy, but chemical reagents introduce pollution and Y2O3 segregates at powder interface
Solution Approach 1:
The patent replaces chemical infiltration methods with mechanical alloying. Instead of using chemical reagents like Y(NO3)3.6H2O solution that cause pollution and segregation, the patent uses mechanical energy from ball milling to disperse and incorporate oxide particles uniformly throughout the alloy matrix.
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 approach achieves a tensile strength of over 1600 MPa at room temperature and 600 MPa at 700°C, with improved high-temperature mechanical properties and elongation, surpassing those of similar alloys, and allows for precise characterization of nano-scale strengthening phases.
Implementation Method 1
mechanical alloying an atomized Fe—Cr—W—Ti pre-alloyed powder and Y2O3 powder
Implementation Method 2
utilizing a combination of milling balls with varying diameters to achieve nano-sized Y2O3 with high-density defects and amorphization
Implementation Method 3
the prepared iron-based alloy powder was hot extruded
Implementation Method 4
hot rolling, and heat treatment
Data Source
AI summary
A multi-scale and multi-phase dispersion strengthened iron-based alloy, and preparation and characterization methods thereof are provided. The alloy contains a matrix and a strengthening phase. The strengthening phase includes at least two types of the strengthening phase particles with different sizes. A volume of the two types of the strengthening phase particles with different sizes having a particle size less than or equal to 50 nm accounts for 85-95% of a total volume of all the strengthening phase particles. The matrix is a Fe—Cr—W—Ti alloy. The strengthening phases include crystalline Y2O3 phase, Y—Ti—O phase, Y—Cr—O phase, and Y—W—O phase. The characterization method comprises electrolytically separating the strengthening phases in the alloy, and then characterizing by using an electron microscope. The tensile strength of the prepared alloy is more than 1600 MPa at room temperature, and is more than 600 MPa at 700° C.