Gradients of Strain to Increase Strength and Ductility of Magnesium Alloys
Abstract
:1. Introduction
2. Materials and Methods
3. Results
3.1. Mechanical Property
3.2. Microstructural Observation
4. Discussion
5. Conclusions
- (1)
- Compared with the initial workpiece, AZ31B processed by ECAP possesses higher yield strength but less ductility; however, AZ31B processed by pure torsion has a higher yield strength with no sacrifice of ductility.
- (2)
- Microstructural observations show that the high strength and high ductility of AZ31B processed by pure torsion can be attributed to the inhomogeneous microstructures, i.e., the gradient of dislocation density combined with dislocation glide and dislocation networks.
- (3)
- Theoretical analyses reveal that plastic deformation leads to the accumulation of statistically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs) result from strain gradient during pure torsion. SSDs help to improve yield strength and GNDs can enhance the ductility by introducing extra work hardening. The combination of SSD and GND can simultaneously improve the strength and ductility of magnesium alloy.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
Appendix A
References
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Elements | Mg | Al | Zn | Mn | Si | Cu | Ca |
---|---|---|---|---|---|---|---|
Wt% | balance | 3.0 | 1.0 | 0.2 | 0.1 | 0.05 | 0.04 |
Parameters | Notation | Value | Source |
---|---|---|---|
Shear modulus | G | 17 GPa | Literature from [19] |
Initial dislocation density | 5 × 1013 m−2 | Literature from [19] | |
Taylor factor | M | 3.06 | Literature from [19] |
Magnitude of Burgers vector | b | 1.29 × 10−10 m | Literature from [19] |
Dislocation storage rate | k1 | 1.4 × 108 m−1 | Literature from [19] |
Dynamic recovery rate | k2 | 8.6 | Literature from [19] |
Grain size of workpiece | 50 μm | Experiment in Figure 1a | |
Yield stress of workpiece | 105 MPa | Experiment in Figure 3 | |
Diameter of bar | d | 4.8 mm | Materials in experiments |
Coefficient in Equation (2) | 0.5 | Literature from [37] |
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Liu, Y.; Cai, S. Gradients of Strain to Increase Strength and Ductility of Magnesium Alloys. Metals 2019, 9, 1028. https://doi.org/10.3390/met9101028
Liu Y, Cai S. Gradients of Strain to Increase Strength and Ductility of Magnesium Alloys. Metals. 2019; 9(10):1028. https://doi.org/10.3390/met9101028
Chicago/Turabian StyleLiu, Yao, and Songlin Cai. 2019. "Gradients of Strain to Increase Strength and Ductility of Magnesium Alloys" Metals 9, no. 10: 1028. https://doi.org/10.3390/met9101028