severe plastic deformation of additive-manufactured alloys

The constant need for high performance engineering components supports the efforts for expanding the design envelopes through the realization of complex shapes and geometries by additive manufacturing. although additive manufacturing can provide the topology, mechanical behavior is inherently limited by the material properties and how the material is built in three dimensions. therefore, research on the improvement of additive-manufactured components from a mechanical behavior perspective has several technological benefits. severe plastic deformation (spd) has long been utilized to achieve extraordinary physical and mechanical properties in a variety of material systems. in this work, we propose the utilization of various spd technologies as post-am processing tools for mechanical response enhancement by highlighting the recent efforts in aluminum alloys and stainless steel. in the first part, we focus on the results concerning alsi12 and alsi10mg, which are common aluminum alloys additive-manufactured via laser powder bed fusion. lpbf processed alsi12 is subjected to multi-pass equal channel angular extrusion/pressing (ecae/p) as an spd technique. following spd, the as-built alsi12 improved monotonic response, where the noticeable enhancement is attributed to the effective grain refinement and the densification provided. a similar approach was followed for lpbf processed alsi10mg, to conclude that the introduction of a refined microstructure decorated with well-distributed precipitates and favorable dislocation substructure improves the resulting mechanical behavior. in addition to the monotonic properties, damping response of the severely deformed alsi10mg is probed with dynamic mechanical analysis experiments. it is observed that damping properties can also be controlled depending on the processing parameters which have direct influence on microstructural evolution. in the second part, emphasis is given to the microstructural modification of additive-manufactured stainless steel (lpbf fabricated 316l alloy) with friction stir processing (fsp). upon fsp, the as-built bimodal microstructure is transformed into the unimodal microstructure containing ultrafine grains. it is revealed that after fsp, a unique improvement in mechanical properties can be obtained due to considerable structural refinement leading to grain boundary strengthening. in addition, it is found that fsp induced severe plastic deformation promotes the transformation of coarse voids to fine voids leading to the densification of the as-built microstructure. with evidence from different materials and spd techniques, this work shows the potential of severe plastic deformation for obtaining unprecedented properties in additive-manufactured alloys. with optimum selection of processing parameters and spd technique-workpiece geometry, it could be possible to implement severe plastic deformation as a regular post-processing tool for as-built additive-manufactured structures.