球化反应是选择性激光熔化（SLM）加工过程中的常见缺陷，是导致成形零件表面粗糙度高、内部出现孔隙、倾斜脱层等现象的主要原因，严重影响零件的致密度及力学性能。对选择性激光熔化成形过程中球化反应的分类及其形成机理、金属球（球化）的形成过程、球化反应的影响因素、球化反应的危害及国内外对球化反应的研究现状进行了比较系统的综述。研究表明球化反应的分类不同其形成机理也不同，球化反应形成过程复杂，影响因素众多，对成形过程及成形件的危害较大。但是目前国内外关于球化反应的研究还不够系统、全面、深入。对工艺参数、金属粉末的物化特性对球化反应的影响等方面进行更加深入的研究，将有利于解决选择性激光熔化成形过程中的球化问题。

Balling phenomena is a common defect in selective laser melting (SLM) process, it is the main reason causing high surface roughness、pores、tilt delamination and other defects, seriously affect the density and mechanical properties of parts. The classification and formation process of balls、influencing factors and hazards of balling phenomena at home and abroad are summarized systematacially. Results show that different metal balls have different formation mechanisms. The formation process of balling phenomena is complex, and many factors during fabricating affect the formation of ball reaction. But the current researches at home and abroad of balling phenomena are not systematic, comprehensive and thorough enough. It will be useful for restraining and eliminating balling phenomena during SLM process to research on the influence of technological parameters, physical and chemical features of powders on balling.