Study On Ultrasonic Impact Treatment Assisted Selective Laser Melting

Selective Laser Melting(SLM)is one of the most promising technologies in the field of addictive manufacturing of metals.This technology has the advantages of high forming precision,good performance of forming parts,which has become a hotspot in the field of large structural parts manufacturing.However,there are many problems which seriously restrict the application and development of SLM.The problems of residual stress,metallurgical defects and grain structure are more prominent,which need to be studied and solved.To overcome these problems,a new method is proposed by combining SLM with ultrasonic impact treatment(UIT)technique.Based on Ti6Al4 V powders,a series of related experimental studies were carried out.The main works are as follows:(1)The single experiments of SLM were explored and the surface topography and defects of the formed parts under different scanning speeds were studied.The experimental results show that high scanning speed(v> 1208)8)/)is unsuitable for powder bed melt process.(2)Based on the single track experiments,the multi-layer forming experiments were carried out.The density behavior of the samples was measured at different scanning speeds and scanning spacings.The internal defects of samples were analyzed,and the formation mechanism of different defects was revealed,and obtains the large thickness process parameters which are suitable for high-efficiency SLM forming.(3)According to the above results,the suitable parameters were selected to design a series of contrast experiments.The feasibility of Ultrasonic Impacted Treatment assisted SLM was investigated and the effects of UIT on the stress,defects and grain structures were analyzed.The results show that in this study,UIT is applied to assist SLM,which successfully reduces the residual stress and defects,and obtains fine equiaxed grains.