A novel rheological high pressure die-casting process for preparing large thin-walled Al-Si-Fe-Mg-Sr alloy with high heat conductivity, high plasticity and medium strength
A novel rheological high pressure die-casting process for preparing large thin-walled Al-Si-Fe-Mg-Sr alloy with high heat conductivity, high plasticity and medium strength
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DOI：
10.1016/j.msea.2020.139040
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发表时间：
2020-03-03
期刊：
影响因子：
6.4
通讯作者：
Li, Jingyuan
中科院分区：
文献类型：
--
作者：
Qi, Mingfan;Kang, Yonglin;Li, Jingyuan
介绍了一种高效制备大体积半固态浆料的风冷搅拌棒法（ACSR）。采用新型低成本铸造Al-Si-Fe-Mg-Sr合金，采用传统HPDC和ACSR流变高压铸造（Rheo-HPDC）工艺制备大型薄壁散热壳体。比较了它们的显微组织、热导率、高温和室温力学性能以及腐蚀行为。此外，本文还分析了ACSR流变HPDC合金组织细化和性能提高的机理。结果表明，采用钢芯铝绞线工艺制备32 kg半固态浆料仅需25 s。采用ACSR Rheo-HPDC工艺制备的合金中生成了大量体积分数大于40%的细小球形初生α-Al颗粒。流变HPDC合金表现出中等强度、高塑性和高导热性。流变HPDC合金的热导率、抗拉强度和延伸率分别为184 W/（m.K）、264 MPa和12.2%，而HPDC合金的热导率、抗拉强度和延伸率分别为167 W/（m.K）、228 MPa和5.8%。ACSR Rheo-HPDC形成的合金的热导率的改善主要归因于共晶硅和富铁的中间体的细化减少了电子散射。这允许电子流更容易地通过共晶Si区域。细化均匀的耐热β-Al 5 FeSi金属间化合物有效地阻止了晶界滑移，使Rheo-HPDC合金表现出上级高温力学性能。流变HPDC合金由于细化了富铁相和共晶硅，降低了基体与富铁相之间的电位差，因而具有比常规HPDC合金更优异的耐腐蚀性能。
An air-cooled stirring rod (ACSR) process for efficiently preparing large volumes of semisolid slurry was introduced. A new low-cost casting Al-Si-Fe-Mg-Sr alloy was used to prepare large thin-walled heat-dissipating shells using both conventional HPDC and ACSR rheological high pressure die-casting (Rheo-HPDC) technologies. Their microstructures, thermal conductivities, elevated temperature and room temperature mechanical properties, and corrosion behaviors were compared. Furthermore, this work analyzed the mechanisms responsible for the microstructure refinement and performance enhancement in ACSR Rheo-HPDC alloys. The results showed that only 25 s was needed to prepare 32 kg of the semisolid slurry using ACSR process. The alloy prepared by ACSR Rheo-HPDC generated a large number of fine spherical primary alpha-Al particles with a volume fraction greater than 40%. The Rheo-HPDC alloy showed a moderate strength, high plasticity, and high heat conductivity. The heat conductivity, ultimate tensile strength and elongation of the Rheo-HPDC alloy were 184 W/(m.K), 264 MPa and 12.2% respectively, while those of the HPDC alloy were 167 W/(m.K), 228 MPa and 5.8% respectively. The improvement of heat conductivity of the alloy formed via ACSR Rheo-HPDC was mainly ascribed to the decrease of electron scattering by the refinement of eutectic silicons and Fe-rich intennetallics. This allowed the electron flow to pass through the eutectic Si region more easily. The refined and uniformly-distributed heat-resistant beta-Al5FeSi intermetallics effectively prevented grain boundary sliding, so the Rheo-HPDC alloy showed superior high-temperature mechanical properties. The Rheo-HPDC alloy presented a more excellent corrosion resistance to the conventional HPDC alloy due to the refinement of iron-rich phase and eutectic silicons and the reduction in the potential difference between the matrix and the iron-rich phase.