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在Al(铝)-Si(硅)合金中同时添加Sr(锶)和B(硼)存在“中毒”现象, 无法同时细化 α-Al晶粒和变质共晶Si. 本文研究了在同时添加 α-Al晶粒细化剂B和共晶Si变质剂Sr的条件下, 微量稀土La(镧)对Al-7%Si-0.6%Fe合金组织、热导率和力学性能的影响, 分析了稀土La的影响规律及其作用机理. 结果表明微量稀土La的添加, 一方面可以中和Sr与B的毒化效应, 提升共晶Si的变质效果; 另一方面可以促使 α-Al异质形核基底LaB 6的形成, 并作为表面活性剂降低 α-Al的形核过冷度, 从而细化 α-Al晶粒. 共晶Si的变质以及 α-Al晶粒的细化有助于同时提升Al-7%Si-0.6%Fe合金的热导率及力学性能. 此外, 当稀土La的添加量在0.02%—0.06%之间时, 合金的导热性能明显提升; 随着La添加量的进一步增大, 合金热导率下降.
Al-Si alloys have been widely used in electronic information, communication, and other fields because of their high specific strength, excellent castability and good thermal conductivity. In recent years, with the rapid development of 5G communication technology, electronic communication equipment is gradually developing towards high integration and lightweight. The power of related equipment is higher and higher, which puts forward higher requirements for thermal conductivity and mechanical properties of materials. Si can improve the fluidity and strength of the Al-Si alloy, but a large amount of Si will aggravate the lattice distortion and increases amount of eutectic Si. This will reduce the plasticity of the alloy, increase the electron scattering and reduce the thermal conductivity. In order to improve the mechanical properties and thermal conductivity of Al-Si alloys, chemical inoculation is generally used. Sr is usually used as modifier and Al-B serves as grain refiner. However, the simultaneous addition of Sr and B into Al-Si alloy results in “poisoning” phenomenon, it becomes impossible to refine α-Al grains and modify eutectic Si simultaneously. In recent years, rare earth La has attracted more and more attention in improving the properties of aluminum alloys. However, previous studies mainly focused on the effects of La addition, consequently, the research on the effects of combined addition of La, Sr, B on the microstructure and properties of Al-7%Si-0.6%Fe alloy is lacking. In this work, solidification experiments are performed to investigate the effects of combined addition of La, Sr, B on the microstructure and properties of Al-7%Si-0.6%Fe alloy. The results show that the addition of trace rare earth La can effectively eliminate the poisoning effect of Sr and B, and enhance the modification effect of eutectic Si. Besides, the addition of La can promote the formation of α-Al heterogeneous nucleation substrate LaB 6and La can be used as a surfactant to reduce the undercooling of α-Al nucleation, thus it refines α-Al grains. The thermal conductivity of the alloy is significantly improved when the addition of La ranges from 0.02% to 0.06%; with the further increase of La addition, LaAlSi intermetallic compounds are formed in the alloy, leading the thermal conductivity of the alloy to decrease. -
Keywords:
- Al-Si alloys/
- micro-alloying element La/
- solidification microstructure/
- thermal conductivity
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Alloy B Sr La Si Fe Al Untreated 0 0 0 7 0.6 余量 0.024%B 0.024 0 0 7 0.6 余量 0.02%Sr 0 0.02 0 7 0.6 余量 0.02%Sr+0.024%B 0.024 0.02 0 7 0.6 余量 0.02%La 0.024 0.02 0.02 7 0.6 余量 0.04%La 0.024 0.02 0.04 7 0.6 余量 0.06%La 0.024 0.02 0.06 7 0.6 余量 0.08%La 0.024 0.02 0.08 7 0.6 余量 0.10%La 0.024 0.02 0.10 7 0.6 余量 
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Alloy TN(α-Al)/K ΔT(α-Al)/K TN(Si)/K ΔT(Si)/K Untreated 883.1 6 846.0 1.1 0.00%La 883.1 3 844.0 3.1 0.04%La 884.2 1.9 843.8 3.3 0.10%La 885.2 0.9 843.8 3.3 下载:
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[100]Al/ [100]SrB6 [100]Al/ [110]SrB6 [100]Al/ [111]SrB6 [110]Al/ [100]SrB6 [110]Al/ [110]SrB6 [110]Al/ [111]SrB6 [112]Al/ [100]SrB6 [112]Al/ [110]SrB6 [112]Al/ [111]SrB6 3.68% 46.63% 79.57% 26.69% 3.68% 26.98% 15.35% 19.72% 46.62% [100]Al/ [100]LaB6 [100]Al/ [110]LaB6 [100]Al/ [111]LaB6 [110]Al/ [100]LaB6 [110]Al/ [110]LaB6 [110]Al/ [111]LaB6 [112]Al/ [100]LaB6 [112]Al/ [110]LaB6 [100]Al/ [111]LaB6 2.67% 45.20% 77.82% 27.40% 2.67% 25.74% 16.17% 18.55% 45.19% 下载:
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(200)Al/ (100)SrB6 (200)Al/ (110)SrB6 (200)Al/ (111)SrB6 (220)Al/ (100)SrB6 (220)Al/ (110)SrB6 (220)Al/ (111)SrB6 (111)Al/ (100)SrB6 (111)Al/ (110)SrB6 (111)Al/ (111)SrB6 3.68% 26.70% 40.23% 46.63% 3.67% 15.47% 79.40% 26.84% 3.42% (200)Al/ (100)LaB6 (200)Al/ (110)LaB6 (200)Al/ (111)LaB6 (220)Al/ (100)LaB6 (220)Al/ (110)LaB6 (220)Al/ (111)LaB6 (111)Al/ (100)LaB6 (111)Al/ (110)LaB6 (111)Al/ (111)LaB6 2.67% 27.41% 40.73% 45.20% 2.65% 16.17% 77.65% 26.60% 2.56% 下载:
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