均匀化退火处理对AZ91镁合金轧制成形行为的影响

Effect of Homogenizing annealing treatment on AZ91 magnesium alloy rolling deformation behavior

摘要:

为改善铸态AZ91镁合金组织不均匀性,提高其轧制成形能力,本文研究了均匀化退火处理对AZ91镁合金轧制变形前后微观组织及力学性能的影响。实验结果表明：均匀化退火处理可以有效改善合金组织中第二相分布；经400℃、多道次轧制后,沿晶界附近分布的细长条状Mg₁₇Al₁₂相数量显著减少,部分脆性Mg₁₇Al₁₂相发生断裂,以小颗粒状弥散分布于晶界附近和基体内部。均匀化后轧制组织比原始轧制组织强度略有提高,而伸长率提高达50%。轧制后的拉伸断口形貌也显示合金塑性得到明显改善。这为后续进一步研究AZ91镁合金在不同工艺参数条件下的轧制成形奠定基础。

Abstract:

To improve the inhomogeneity and rolling forming ability of as-cast AZ91 magnesium, the effect of homogenizing annealing treatment on microstructure and mechanical properties of AZ91 magnesium alloy before and after rolling deformation was studied. The results showed that the distribution of second phase in the alloy tissue was improved effectively after homogenization annealing treatment. After multi-pass rolling at 400℃, the thin strip Mg₁₇Al₁₂ phase which originally distributed along the grain boundaries reduces significantly, with some of them fragmented, and some distributed near the grain boundaries or inside the grains as small particles. Compared with the strength of as-cast rolling structure, the strength of rolling structure after homogenization increases slightly; while the elongation increases by 50%.The tensile fracture morphology after rolling also shows that the ductility of alloy improves significantly. This lays a foundation for further study on the rolling forming of AZ91 magnesium alloy under different technological parameters.