Journal of Materials Research and Technology (Nov 2024)

Microstructure and dynamic deformation mechanism of laser powder bed fusion of 316L-containing Ti–6Al–4V with dual-phase heterostructure

  • Kekang Zhang,
  • Jinhui Meng,
  • Yixiong Hu,
  • Zhenduo Chen,
  • Yang Liu

Journal volume & issue
Vol. 33
pp. 5976 – 5986

Abstract

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In this paper, 316L-containing Ti–6Al–4V alloy was fabricated by laser powder bed fusion (LPBF) through mixing Ti–6Al–4V and 4.5 wt% 316L powders, and the dynamic compressive mechanical properties and deformation mechanism at different strain rates were studied. The results show that the volume fraction of β phase sharply increases from 1.8% (in TC4) to 61.4% (in HST), and micro- and submicron-sized grains coexist in the HST alloy, producing heterostructure in the form of bimodal grain size distribution. The presence of the heterostructure led to superior heterogeneous deformation induced stress, thus facilitating the additional strain hardening and deformation coordinating ability, thus made the HST alloy achieved ultimate compressive stress of ∼1750 MPa and fracture strain of ∼17%, showing excellent comprehensive mechanical properties. Under quasi-static load, the deformation mode of HST alloy is mainly attributed to progressive deformation-induced martensitic transformation. However, at high strain rates, the impact loading inhibited the activation of progressive DIMT, and thus the deformation mode changed to combination of dislocation slipping and deformation twinning.

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