中文摘要：

使用激光近净成形方法，在Ti-6A1-4V基板上进行高纯Al2O3成形实验，分别制备出黑色和白色Al2O3薄壁样品。利用扫描电子显微镜观察样品截面微观组织并检测截面化学元素。利用x射线衍射仪分析原始Al2O3粉末、黑色样品和白色样品的物相组成、成色原因以及成形件样品表面裂纹数量与颜色之间的关系。结果表明：黑色薄壁样品表面裂纹数量多、分布均匀；白色薄壁样品仅中上部含有极少量裂纹。成形工艺可显著影响陶瓷粉末中杂质氧化物的挥发程度，进而影响成形件样品元素组成及物相。次晶相的出现是成形件样品颜色发黑的根本原因，并加剧了黑色样品表面裂纹的产生与扩展。

英文摘要：

High-purity Al2O3 ceramic was formed on a Ti-6AI-4V substrate via laser engineered net shaping （LENS）. The black and white thin-wall samples were produced, respectively. The microstructure and chemical elements of the samples＇ cross section were analyzed by scanning electron microscope. The phase compositions of the original A1203 powder, the black sample and the white sample, the color difference of the samples and the relationship between the amount of surface cracks and the color of the samples were investigated. The results show that the black thin-wall sample has many evenly-distributed surface cracks, and the white thin-wall sample contains a few surface cracks only on the upper part. The formation process affects the volatility degree of oxide impurities in the particles, and the chemical elements and phase compositions in the samples. The emergence of the second phase is a major cause to obtain the black sample and promote the formation and propagation of the surface cracks in the black sample.