Abstract
Laser beam powder bed fusion (PBF-LB) additive manufacturing (AM) is an advanced manufacturing technology that manufactures metal components in a layer-by-layer manner. The thermal residual stress (RS) induced by the repeated heating–melting–cooling–solidification processes of AM is considered to limit the wider uptake of PBF-LB. A dual-laser beam PBF-LB strategy, with an additional auxiliary laser and reduced power, working in the same powder bed simultaneously, was recently proposed to lower RS within the manufactured components. To provide insights into the optimum PBF-LB AM configurations and process parameters for dual-laser PBF-LB, this study proposed three different coordinated heating strategies (i.e., parallel heating, post-heating, and preheating) of the auxiliary heat source. The temperature fields and RS of dual-laser beam PBF-LB, for Ti-6Al-4V with different process parameters, were computationally investigated and optimized by the thermo-mechanically coupled 3D models. Compared with the single beam PBF-LB, parallel heating, post-heating, and post-heating strategies were proved as effective approaches to reduce RS. Among these, the preheating scanning is predicted to be more effective in mitigating RS, i.e., up to a 10.41% RS reduction, compared with the single laser scanning. This work could be beneficial for mitigating RS and improve the mechanical properties of additively manufactured metal components.
Highlights
Laser beam powder bed fusion (PBF-LB) is one of the most commonly used additive manufacturing (AM) technologies for bespoke component manufacturing in industry [1–3]
For better control of the thermal history, microstructure, and mitigation of the residual stress (RS) [9], a novel duallaser beam PBF-LB was recently presented as a promising technique [10], where a laser beam with enough power to melt the powders and a secondary laser with reduced power to slow the cooling process during PBF-LB
With dual-laser beams working simultaneously on the same powder bed, the total energy input and cooling rate could be significantly changed in dual-laser PBF-LB, compared to that of the single laser PBF-LB
Summary
Laser beam powder bed fusion (PBF-LB) is one of the most commonly used additive manufacturing (AM) technologies for bespoke component (e.g., orthopedic implant) manufacturing in industry [1–3]. Zhang et al [15] examined the effects of scanning strategies on temperature, RS, and deflection, and the results indicated that multi-laser beam PBF-LB could mitigate the maximum RS by 16.5%, compared with that of the single laser PBF-LB. Heeling et al [16] investigated the melt pool characteristic of multi-beam PBF-LB by using a high speed camera, and the addition of a preheating laser was proved to effectively reduce the spatter phenomenon. The build process parameters, such as energy beam power and moving speed, influence the RS within additively manufactured components and have been widely investigated in the single laser beam PBF-LB [5,17]. The “S” scanning strategy was employed in PBF‐LB process modelling and rotated 90° for the subsequent layer (Figure 3). FiFgiguurere22..IIlllluussttrraattiioonnoofftthhrereeeddiffieffreernetnmt omdoesdoefsaosfeacosnedcoanrydlaarsyerlabseearmb: e(aa)mp:a(raa)llpelamraoldleel; m(bo) dpoe;st(-b) post‐ hehaeatitninggmmooddee;; aanndd((cc))pprerheheaetaintignmg omdoed. e
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