长江中游地区楚墓中出土的青铜箭镞的锈蚀现象及锈蚀机理研究

Study of rust-eaten phenomenon and mechanism of bronze arrows excavated from Chu tombs in middle Yangtse river region

青铜箭镞是古代制造量最大、一次性使用的兵器,与要求甚高的青铜剑和青铜礼乐器等相比,在选材和表面处理等方面有很大的不同,其锈蚀过程最能反映材料在经过数千年后所产生变化。长江中下游地区环境潮湿,埋藏条件复杂,本研究利用扫描电子显微镜(SEM)、能谱仪(EDS)、X-射线衍射仪(XRD)、显微硬度等分析测试技术,从材料科学的角度对长江中游地区战国晚期古墓中出土的青铜箭镞的锈蚀现象和锈蚀机理进行了全面的研究和分析,以期为古代青铜器的保护提供更准确的信息和资料。结果表明,青铜箭镞的组织结构可分为完全矿化层、过渡层和心部原始材料等三个特征层,不同特征层具有不同的显微组织、化学成分、致密性,以及显微硬度等;并沿横截面观察和分析了锈蚀层中的微裂纹的性质和产生原因,即,平行于表面的裂纹是由矿化层氧化物膨胀引起的剥离开裂,其进一步发展将形成"粉状锈",而垂直于表面呈放射状的裂纹是当圆柱形箭镞杆膨胀时,矿化层的塑性差,抗变形能力低而产生的开裂;锈蚀机理研究认为青铜器的锈蚀过程是环境中杂质元素通过过渡层沿界面能较高的α固溶体和(α+δ)共析体晶界或孔隙等缺陷逐步向内部扩散的结果。

In the Chinese ancient times around 200 B. C. ,bronze arrow was a kind of weapons in mass manufacturing and one - off use. Comparing to the strict demanded bronze sward and ritual vessel - Ding,the low performance bronze arrows exhibited a great difference in material selection and surface treatment. Therefore, the rust - eaten process of the arrows will really represent a variation of the materials after several thousand years, especially, in the complicated environments in the middle Yangtse River region. This paper studies the rust - eaten phenomenon and mechanism of the bronze arrows made in late Spring - Autumn age by using scanning electron microscopic （ SEM）, energy - disperse spectrometer （EDS）, X- ray diffraction （XRD） and microhardness tester. It was found that the microstructures of bronze arrows were composed of three distinctive layers including a completely mineralized layer, transition layer and core original material. Different layers exhibited different microstructures, chemical compositions, compatibility and microhardness. The formation mechanism of the micro - cracks in the cross - section rust - eaten layer was firstly observed and analyzed,i, e. ,the crack paralleling to the surface was caused due to expanse disbonding in the mineralized layer which would further develop into a ＂rust powder＂ ,while the radial crack perpendicular to the surface was due to the arrow rod expansion in the poor ductility mineralized layer. It is considered that the rust - eaten process of bronze is the result of impurity diffusion gradually along the grain boundaries between α solid solution and α ＋ δ eutectoid grains, cavities and other defects where possess higher boundary energy in atmospheric environment.