Synthesis of Nanocrystalline AZ91 Magnesium Alloy Dispersed with 15 vol.% Submicron SiC Particles by Mechanical Milling
Abstract
:1. Introduction
2. Experimental
2.1. Mechanical Milling Process
2.2. Microstructural Characterization
3. Results and Discussion
3.1. Characterization of Initial Materials
3.2. Morphology Evolution
3.3. Dispersions Evolution
3.4. Phase Transformation
3.5. Magnesium Matrix Analysis
3.6. Hardness Analysis
4. Conclusions
- (1)
- The addition of submicron SiCp accelerated the smashing of AZ91 particles during mechanical milling, which assisted in the dispersion of SiCp in the Mg matrix. After mechanical milling, the average particle size decreased from 800 to 255 nm, and the tiny SiCp, including some nanometer particles, was distributed uniformly in the Mg matrix.
- (2)
- During mechanical milling, powders are in a nonequilibrium state. The dissolution of Mg17Al12 precipitates was confirmed. Based on the lattice parameter evolution of the Mg matrix, Al-supersaturated Mg solid solution was formed. There were also some Mg17Al12 precipitates remaining, the pattern of which changed into particle with diameter of about 700 nm. Moreover, it was found that the SiCp dispersed in Mg matrix hindered the dissolution of Mg17Al12 precipitates.
- (3)
- After mechanical milling, NC AZ91 and SiCp/AZ91 were achieved. Meanwhile, due to the pinning effect on the movement of dislocations, the dislocation pile-up of SiCp/AZ91 was accelerated. Thus, the average grain size of milled SiCp/AZ91 (~32 nm) was smaller than that of milled AZ91 (~64 nm).
- (4)
- After mechanical milling, the hardness of SiCp/AZ91 was approximately 185 HV, which was 185% higher than that of the initial AZ91. The strengthening mechanisms of SiCp/AZ91 were analyzed quantitatively. The contribution ratio of grain boundary strengthening, solid solution strengthening, Orowan strengthening, and load-bearing strengthening to milled SiCp/AZ91 were about 81.5%, 1.5%, 6.8%, and 10.3%, respectively. Meanwhile, due to the addition of submicron SiCp, the hardness of SiCp/AZ91 increased by 33% compared with milled AZ91 due to Orowan strengthening, load-bearing strengthening, and more enhanced grain boundary strengthening.
Author Contributions
Funding
Conflicts of Interest
References
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Materials | Particle Size (μm) | Grain Size (μm) | Hardness (HV) | Processing |
---|---|---|---|---|
AZ31B | - | 0.12 | 123 | HPT [35] |
Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr | - | 0.10 | 145 | HPT and annealing [19] |
AZ61-8 vol.% Ti | 0.36 | 0.05 | 147 | MM [7] |
Mg-1.11 vol.% Al2O3 | <0.1 | 31 | 70 | MM and sintering [36] |
Mg-2.5 wt.% TiB2 | 0.1–0.7 | - | 107 | As-cast [37] |
Mg18Zn-6 vol.% SiCp | 0.05 | - | 183 | NSP [34] |
Mg-10 vol.% SiCp | 0.05 | 0.06 | 141 | MM [38] |
Mg-10 vol.% SiCp | 0.05 | 0.16 | 99 | MM and ES [38] |
AZ91-15 vol.% SiCp* | 10 | 48 | 133 | Thixoforging [39] |
AZ91-15 vol.% SiCp | 0.26 | 0.03 | 185 | MM |
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Su, S.; Zhou, J.; Tang, S.; Yu, H.; Su, Q.; Zhang, S. Synthesis of Nanocrystalline AZ91 Magnesium Alloy Dispersed with 15 vol.% Submicron SiC Particles by Mechanical Milling. Materials 2019, 12, 901. https://doi.org/10.3390/ma12060901
Su S, Zhou J, Tang S, Yu H, Su Q, Zhang S. Synthesis of Nanocrystalline AZ91 Magnesium Alloy Dispersed with 15 vol.% Submicron SiC Particles by Mechanical Milling. Materials. 2019; 12(6):901. https://doi.org/10.3390/ma12060901
Chicago/Turabian StyleSu, Shitian, Jixue Zhou, Shouqiu Tang, Huan Yu, Qian Su, and Suqing Zhang. 2019. "Synthesis of Nanocrystalline AZ91 Magnesium Alloy Dispersed with 15 vol.% Submicron SiC Particles by Mechanical Milling" Materials 12, no. 6: 901. https://doi.org/10.3390/ma12060901