Distortion mitigation in additive manufacturing of AlSi10Mg by multilayer laser peening

Distortion in metal additive manufacturing remains an industry barrier due to the inadequate thermal management that gives rise to residual stresses. Mitigation strategies primarily involve developing a print recipe based on the build material; however, variability among machine platforms, build strategies, and raw material stock inhibit development of universal print recipes that eliminate distortion. There is a need for a universal manufacturing technology that enables distortion free additive manufacturing. A solution to provide distortion free parts that are machine platform and build strategy independent is coupling additive manufacturing with multilayer peening. Peening enables favorable redistribution of residual stresses that drive distortion using mechanical means rather than thermal management. The cumulative nature of residual stress during layer-by-layer peening and the compounding effect on distortion is poorly understood. Thus, the research objective of this work was to measure residual stress and distortion after multilayer laser peening on AlSi10Mg printed by laser powder bed fusion on the Matsuura Lumex Avance-25. Residual stress was measured for several interlayer peening frequencies. An optimum condition was identified and evaluated for distortion mitigation. To measure deflection, bridge samples based on NIST AMB2018-01 were printed and interlayer peened. Results indicated that laser peening reduced distortion 45% over an as-printed sample.