打印角度对SLM增材制造Al250C铝合金的残余应力影响分析

Effect of building direction on the residual stresses in Al250C aluminum alloy fabricated by SLM

摘要:

激光选区融化Selective Laser Melting（SLM）作为先进的增材制造技术（又称3D打印）受到高附加值的航空航天产业特别关注，但是在SLM过程中不断重复的融化和凝固过程导致残余应力的出现，残余应力会导致几何变形、内部裂纹及零件在交变载荷或腐蚀环境下过早失效等各种问题．利用SLM技术基于不同打印方向制造Al250C铝合金样品，并且使用小孔法测量样品的残余应力．由于增材制造技术生产的金属部件的微观结构具有各向异性、强织构和微观偏析等特点，为了提高小孔法测量结果的可靠性，打印样品的材料各向异性特征需要考虑到残余应力的数据分析中．通过实验测量结果可以发现，打印方向对样品中的残余应力分布有显著的影响，使用各向异性和各向同性的材料系数分析残余应力的结果差别可达70 MPa.

Abstract:

Selective laser melting （SLM） as an advanced additive manufacturing technology has drawn high attention from high-value aircraft and aerospace industries. Due to repeat heating-cooling phenomenon in the SLM process， the residual stresses are formed. The residual stresses can lead to geometric distortion， built-in cracking or premature failure of parts subjected to alternating loading or corrosive environments. The objective of this work is to fabricate Al250C aluminum alloy samples using the SLM technology with different building directions， as well as to measure the residual stresses through hole drilling method （HDM）. The printed samples are characterized by the strong texture and anisotropy. For improving the reliability of the residual stress analysis， these factors are accounted for in the present work. Through the measurement results， it can be found that the building direction has a significant influence on the residual stress profile in the samples. Also， it is found that the difference in stress values between anisotropic and isotropic parameters used for residual stress evaluation can be over 70 MPa.