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研究了添加Si对Zn-38Al-2.5Cu合金显微组织、力学性能及热疲劳性能的影响。结果表明:Si的添加使锌铝合金产生成分过冷。当Si添加量为0.55%时,合金组织细化显著,力学性能最优。继续添加Si,Si相聚集长大,晶粒粗化,合金力学性能下降。由于塑性变形形成的凹坑及氧化是热疲劳裂纹萌生的主要原因。在裂纹扩展前期,裂纹附近形成的疏松多孔的氧化区加快裂纹生长,符合Paris公式,裂纹主要沿晶界扩展。裂纹扩展后期,二次裂纹的快速生长吸收了主裂纹生长所需的部分能量,裂纹进入缓慢增长阶段,裂纹变为沿晶和穿晶混合的扩展特征。
The effects of Si addition on the microstructure, mechanical properties and thermal fatigue properties of Zn-38Al-2.5Cu alloy were investigated. The results show that the addition of Si makes the composition of Zn-Al alloy to be too cold. When the content of Si is 0.55%, the microstructure of the alloy is refined remarkably and the mechanical properties are optimal. Continue to add Si, Si phase aggregation grow, grain coarsening, mechanical properties of alloys decreased. Depression and oxidation due to plastic deformation are the main causes of thermal fatigue crack initiation. In the early stage of crack propagation, the porous and porous oxide zone formed near the crack accelerates crack growth, which accords with the Paris formula. The crack propagates mainly along the grain boundary. In the late stage of crack growth, the rapid growth of secondary cracks absorbed some of the energy required for the growth of the primary crack, and the cracks entered a slow growth phase. The crack became an extended characteristic of intergranular and transcrystalline mixing.