Reduction of residual stress in porous Ti6Al4V by in situ double scanning during laser additive manufacturing


Selective laser melting (SLM) technology plays an important role in the preparation of porous titanium (Ti) implants with complex structures and precise sizes. Unfortunately, the processing characteristics of this technology, which include rapid melting and solidification, lead to products with high residual stress. Herein, an in situ method was developed to restrain the residual stress and improve the mechanical strength of porous Ti alloys during laser additive manufacturing. In brief, porous Ti6Al4V was prepared by an SLM three-dimensional (3D) printer equipped with a double laser system that could rescan each layer immediately after solidification of the molten powder, thus reducing the temperature gradient and avoiding rapid melting and cooling. Results indicated that double scanning can provide stronger bonding conditions for the honeycomb structure and improve the yield strength and elastic modulus of the alloy. Rescanning with an energy density of 75% resulted in 33.5%–38.0% reductions in residual stress. The porosities of double-scanned specimens were 2%–4% lower than those of single-scanned specimens, and the differences noted increased with increasing sheet thickness. The rescanning laser power should be reduced during the preparation of porous Ti with thick cell walls to ensure dimensional accuracy.

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This work was financially supported by the National Natural Science Foundation of China (Nos. 52004026 and 51725401) and the Fundamental Research Funds for the Central Universities, China (No. FRF-TP-18-003C2). The helpful comments, suggestions, and encouragement from the editors and anonymous reviewers are gratefully acknowledged.

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Correspondence to Shu-qiang Jiao.

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Luo, Yw., Wang, My., Tu, Jg. et al. Reduction of residual stress in porous Ti6Al4V by in situ double scanning during laser additive manufacturing. Int J Miner Metall Mater (2021).

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  • porous titanium
  • selective laser melting
  • additive manufacturing
  • residual stress
  • mechanical properties