目的 揭示Sc/Zr复合微合金化对A356铝合金微观组织、力学性能及耐蚀性能的协同调控机制,为高性能铸造铝合金的成分设计与精密成形组织控制提供理论依据。方法 在固定Zr含量（约0.05%,质量分数）的基础上,通过调控Sc添加量制备试验合金,结合T6热处理工艺,利用OM、SEM及EDS等手段深入分析了α-Al晶粒、共晶Si相及Al3(Sc,Zr)纳米析出相的组织演变规律,并系统评估了合金在180 ℃下的硬度时效特性、强塑性匹配及中性盐雾腐蚀行为。结果 试验合金均在180 ℃时效10 h后达到硬度峰值,Sc/Zr原子比为1∶1的合金表现出最优的强塑性匹配。尽管增加Sc含量可将α-Al晶粒显著细化至约80.9 μm,但过量Sc会引发Al3(Sc,Zr)析出相粗化与严重的成分偏析,导致时效稳定性下降,并显著加剧晶间腐蚀敏感性。在盐雾腐蚀环境下,合金强度因腐蚀损伤有所降低;但Sc含量增加可细化微观组织,降低局部点蚀倾向并抑制微裂纹萌生,使合金塑性显著升高。结论 Sc/Zr通过细晶强化与析出强化的协同作用大幅提升A356合金的综合性能,且明确了1∶1的Sc/Zr配比是实现组织细化与性能提升的最佳微合金化设计。
Abstract
The work aims to elucidate the synergistic regulation mechanisms of Sc/Zr composite microalloying on the microstructure, mechanical properties, and corrosion resistance of A356 aluminum alloy, thereby providing a theoretical basis for the composition design of high-performance cast aluminum alloys and the control of microstructure during precision forming. Experimental alloys were prepared by adjusting the Sc addition level while keeping the Zr content constant (approximately 0.05wt.%). Combined with the T6 heat treatment process, OM, SEM, and EDS were employed to thoroughly analyze the microstructural evolution of α-Al grains, eutectic Si phases, and Al3(Sc,Zr) nano-precipitates. Furthermore, the alloy's hardness aging behavior at 180 ℃, strength-to-ductility ratio, and neutral salt spray corrosion behavior were systematically evaluated. All experimental alloys reached their peak hardness after 10 h of aging at 180 ℃, with the alloy having a Sc/Zr ratio of 1∶1 exhibiting the optimal balance of strength and ductility. Although increasing the Sc content could significantly refine the α-Al grains to approximately 80.9 μm, an excess of Sc led to coarsening of the Al3(Sc, Zr) precipitation phase and severe compositional segregation, resulting in reduced aging stability and significantly increased susceptibility to intergranular corrosion. Under salt spray corrosion conditions, the alloy's strength was reduced due to corrosion damage. However, increasing the Sc content refined the microstructure, reduced the tendency for localized pitting corrosion, and suppressed microcrack initiation, resulting in a significant increase in the alloy's ductility. The synergistic effects of grain refinement and precipitation hardening through Sc/Zr can substantially improve the comprehensive properties of A356 alloy, and it has been established that a 1∶1 Sc/Zr ratio is the optimal microalloying design for achieving microstructural refinement and performance enhancement.
关键词
A356铝合金 /
Sc/Zr微合金化 /
析出相 /
力学性能 /
耐蚀性能
Key words
A356 aluminum alloy /
Sc/Zr microalloying /
precipitated phase /
mechanical properties /
corrosion resistance
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基金
国家重点研发计划（2022YFB4300105）; 国家自然科学基金面上项目（52475346）; 湖南省自然科学基金（2025 JJ70085）; 湖南省科技创新计划（2025RC4011）
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