针对某N型锌铝合金时效处理后硬度降低的问题，对该锌铝合金试样进行了硬度测试、化学成分分析、金相检验、扫描电镜分析、能谱分析、材料热处理性能分析和热处理验证试验。结果表明：该N型锌铝合金是在ZA50型系列锌铝合金的基础上开发得到的，其热处理后硬度降低的主要原因是时效处理的温度过高、时间过长，出现了过时效现象。最后针对该N型锌铝合金的硬度要求，提出了改善措施。

Aiming at the issue of hardness reduction of some N type zinc-aluminium alloy after aging treatment, the zinc-aluminium alloy specimens were analyzed by hardness testing, chemical composition analysis, metallographic inspection, SEM analysis, EDS analysis, material heat treatment performance analysis and heat treatment verification testing. The results show that the N type zinc-aluminium alloy was developed on basis of the ZA50 type zinc-aluminium alloy series. The main reasons of hardness reduction after heat treatment were that the temperature of aging treatment was too high and the holding time of aging treatment was too long, causing the overaging phenomenon. At the end, some improving methods were suggested to meet the hardness requirement of the zinc-aluminium alloy.