Effect of Mg on microstructure and mechanical properties of in-situ TiB2/Al-4.5Cu composites
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摘要: 采用Al-K2TiF6-KBF4混合盐原位自生反应法,制备了不同Mg质量分数的3wt% TiB2/Al-4.5Cu复合材料。采用SEM、TEM、HM硬度测试和室温拉伸等方法研究了Mg含量和多级热处理对3wt% TiB2/Al-4.5Cu复合材料微观组织和力学性能的影响。微观组织观察发现:Mg质量分数为3wt%时,经过多级热处理后,TiB2颗粒的团聚现象明显改善,反应生成的TiB2颗粒平均尺寸约为130 nm,基体内伴随有大量弥散分布的纳米级颗粒,且α-Al的晶粒尺寸也明显减小。力学测试结果表明:多级热处理后,3wt% TiB2/Al-4.5Cu复合材料的硬度和抗拉强度随Mg含量的增加而提高,但过量的Mg (≥4wt%)会造成TiB2颗粒细化效果下降。分析表明:Mg的加入能够降低TiB2/α-Al界面能,减少脆性相Al3Ti、Al2B的生成,并通过反应生成的MgAl2O4使界面结构变成TiB2/MgAl2O4/α-Al,从而有效抑制了TiB2的团聚,改善了TiB2颗粒与Al液界面的润湿性,提高了形核率,进一步细化了α-Al晶粒尺寸。
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关键词:
- TiB2/Al-4.5Cu复合材料 /
- Mg /
- 微观组织 /
- 硬度 /
- 力学性能
Abstract: The 3wt% TiB2/Al-4.5Cu composites with different mass fraction of Mg were fabricated by Al-K2TiF6-KBF4 molten salt reaction method. The influences of Mg and multistage heat treatment on the microstructure and mechanical properties of the 3wt% TiB2/Al-4.5Cu composite were studied by means of SEM, TEM, HM hardness test and room temperature tensile test. The microstructure observation shows that the agglomeration of TiB2 particles is obviously improved after multistage heat treatment along with addition of Mg, In particular, with 3wt% Mg, the average size of TiB2 particles is about 130 nm, accompanied by a large number of dispersed nano particles, and the grain size of α-Al is also significantly reduced. The mechanical test results show that after multistage heat treatment, the hardness and tensile strength of the 3wt% TiB2/Al-4.5Cu composite are enhanced with the increase of Mg content. However, excess Mg content (mass fraction≥4wt%) will decrease the refinement effect of TiB2 particles. The analysis reveals that addition of Mg can reduce the interfacial energy of TiB2/α-Al and block the formation of brittle phase Al3Ti, Al2B. Meanwhile, the MgAl2O4 formed by reaction makes the interface become into the TiB2/MgAl2O4/α-Al, which could restrain the agglomeration of TiB2 particles and improve the wettability of the interface between TiB2 particles and Al liquid, increase the nucleation rate and refine the grain size.-
Key words:
- TiB2/Al-4.5Cu composites /
- Mg /
- microstructure /
- hardness /
- mechanical properties
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图 2 3wt% TiB2/Al-4.5Cu复合材料多级热处理后TiB2颗粒的微观形貌: (a)不含Mg; (b) 1wt% Mg; (c) 2wt% Mg; (d) 3wt% Mg; (e) 4wt% Mg; (f) 4.5wt% Mg
Figure 2. Morphologies of TiB2 particles in multistage-heat treated 3wt% TiB2/Al-4.5Cu composites: (a) Without Mg; (b) 1wt% Mg; (c) 2wt% Mg; (d) 3wt% Mg; (e) 4wt% Mg; (f) 4.5wt% Mg
图 4 多级热处理前后3wt% TiB2/Al-4.5Cu复合材料力学性能随Mg质量分数的变化: (a)室温拉伸强度; (b)延伸率; (c)微观硬度(HB)
Figure 4. Mechanical properties of 3wt% TiB2/Al-4.5Cu composites varying with Mg mass fraction before and after multistage heat treatment: (a) Tensile strength; (b) Elongation; (c) Micro hardness (HB)
Rm—Tensile strength; Rp0.2—Proof strength
表 1 实验所用原料
Table 1. Raw materials of experiment
Raw material Al Mg Al-50Cu KBF4 K2TiF6 Na3AlF6 Purity/% >99.9 >99.9 >99.9 99.99 99.99 99.99 -
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