本文用金相、显微硬度、x射线衍射、电子探针等多种分析技术研究了热镀铝层的显微组织及成分。结果证明,A_3钢热镀铝层是由表面富铝层和以Fe_2Al_5为主要相成分的扩散层所组成,对此作出了理论解释。此外,还对热镀铝层中的扩散层(Fe_2Al_5相)的长大规律进行了讨论,并在此基础上确定了扩散层厚度与浸铝时间、浸铝温度的依赖关系: h=1.04×10~(-4)t~(1/2)·exp(-(29260/RT))cm In this paper, the microstructure and composition of hot-dip aluminized layer were studied by metallographic analysis, microhardness, x-ray diffraction and electron probe. The results show that, A 3 steel aluminized layer is composed of the surface of the aluminum-rich layer and Fe 2 Al_5 as the main component of the diffusion layer composed of a theoretical explanation. In addition, the law of growth of the diffusion layer (Fe 2 Al 5 phase) in the hot-dip aluminizing layer was also discussed. On the basis of this, the dependence of the thickness of the diffusion layer on the leaching time and the temperature of the aluminum immersion was determined: h = 1.04 × 10 ~ (-4) t ~ (1/2) · exp (- (29260 / RT)) cm