Quantification of Microstructural Features and Prediction of Mechanical Properties of a Dual-Phase Ti-6Al-4V Alloy
Abstract
:1. Introduction
2. Experimental Procedure
2.1. Materials
2.2. Cutting Experiments
2.3. Samples Preparation
3. Inspection of the Microstructural Features
3.1. Qualitative Description
3.2. Quantitative Identification
3.2.1. Proposed Method
- (1)
- The original image was entered into Matlab software with an uncompressed tagged image file format. Cropping, smoothing, and sharpening were then carried out to eliminate image defects, such as uneven brightness;
- (2)
- Noise reduction of the digital image using a Gaussian low-pass filter;
- (3)
- Implement the Canny edge detection algorithm after executing image graying;
- (4)
- Superposition of the images, which are processed by step (1) and step (3), to add contrast between the α and β phases;
- (5)
- The gray image was transformed into a binary image. The image matrix of the binary image only consists of pixel values “0” and “1”, where “1” represents the α phase, and “0” represent the β phase;
- (6)
- Extract the density of the constituent phases per square micron. The distribution gradients of the constituent phases beneath the machined surface are then obtained; and
- (7)
- Lamellar α + β colonies were regarded as a single β phase, and then profiles of the α phase were picked up. The size distribution and mean diameter of α grains were then calculated using Image-P Plus software. The statistics cover the whole SEM image with a size of 244 μm × 167 μm. The mean diameter is the average length of diameters measured at 2 degree intervals and passing through the profile centroid of the α phase.
3.2.2. Identification Results
3.3. Milling Parameter Sensitivity Analysis
4. Mechanical Property Optimization
5. Conclusions
- A digital image processing method was proposed. The new approach is based on the fact that the constituent phases of Ti-6Al-4V titanium alloy show different gray levels in digital images. By the proposed method, microstructural features, including the content of constituent phases and grain size, were identified. A high content of the β phase and small grain size were found at the machined surface. The maximum measured values of change rate of β phase, grain refinement rate at the machined surface, and thickness of the deformation layer are 141.1%, 47.2%, and 12.3 μm, respectively.
- Sensitivity of microstructural changes to milling parameters was investigated. The thickness of the deformed layer and grain refinement rate decreased distinctly with the increase of the cutting speed, but increased with the increase of the feed rate. The parameter of the depth of cut played a positive role in increasing the thickness of the deformed layer, while opposite to the grain refinement rate. For the variation of the change rate of the β phase at the machined surface, the depth of cut is the foremost factor among the three studied parameters.
- Stress-strain behavior of two ductile phase alloys was developed using the finite element method. A high content of the β phase was found to have a high strength of materials. Values of yield strength varied from 889–921 MPa with the change of content of the β phase from 30%–45%.
Acknowledgments
Author Contributions
Conflicts of Interest
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Levels/Factors | Cutting Speed vc (m/min) | Feed Rate fz (mm/z) | Radial Depth of Cut ae (mm) |
---|---|---|---|
Level 1 | 20 | 0.02 | 0.5 |
Level 2 | 50 | 0.03 | 1.0 |
Level 3 | 80 | 0.04 | 1.5 |
Level 4 | 110 | 0.05 | 2.0 |
Phase | σy (MPa) | E (GPa) | N | |
---|---|---|---|---|
α | 345 | 140 | 17.959 | 3.484 |
β | 1000 | 170 | 8.246 | 5.305 |
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Yang, D.; Liu, Z. Quantification of Microstructural Features and Prediction of Mechanical Properties of a Dual-Phase Ti-6Al-4V Alloy. Materials 2016, 9, 628. https://doi.org/10.3390/ma9080628
Yang D, Liu Z. Quantification of Microstructural Features and Prediction of Mechanical Properties of a Dual-Phase Ti-6Al-4V Alloy. Materials. 2016; 9(8):628. https://doi.org/10.3390/ma9080628
Chicago/Turabian StyleYang, Dong, and Zhanqiang Liu. 2016. "Quantification of Microstructural Features and Prediction of Mechanical Properties of a Dual-Phase Ti-6Al-4V Alloy" Materials 9, no. 8: 628. https://doi.org/10.3390/ma9080628