Effects of boron addition on microstructures and mechanical properties of Ti-6Al-4V manufactured by direct laser deposition

Grain Refinement of Alloys in Fusion-Based Additive Manufacturing Processes

“…Consequently, boron has been used to refine the grain size in Ti alloys produced by WAAM [81,82] and laser-directed energy deposition (L-DED, often known as laser metal deposition (LMD)). [83][84][85][86][87] Other growth restricting solutes including carbon, [80] tungsten, [79] silicon, [88] copper, [68] nickel [89] , and chromium [26] have also proven to be effective in b-Ti grain refinement during AM. Broadly speaking, the effectiveness of solutes in refining b-Ti grains during AM is in line with their growth restriction factor.…”

“…Such particles have [83]; (d) The effect of growth restricting solute on the grain size of Ti alloy produced by AM (increasing Q causes significant reduction in grain size). [26,80,81,83,86,88] Relative grain size is expressed as a fraction of 1 which represents the base unrefined alloy, such as Ti-6Al-4V. (e, f) Polarized optical microscopy images showing the equiaxed grains of as-printed Ti-3.5Cu and Ti-6.5Cu alloys produced by L-DED, reprinted from Ref.…”

“…[80]; (c) Refinement of b-Ti grains during L-DED with boron addition, adapted from Ref. [83]; (d) The effect of growth restricting solute on the grain size of Ti alloy produced by AM (increasing Q causes significant reduction in grain size) [26,80,81,83,86,88]. Relative grain size is expressed as a fraction of 1 which represents the base unrefined alloy, such as Ti-6Al-4V.…”

Ordered nitrogen complexes overcoming strength–ductility trade-off in an additively manufactured high-entropy alloy

“…Based on the plasticity theory (Song et al 2019;Ma and Zhu 2017), the coarse grains yield first during deformation, then the plastic deformation is constrained by the relative harder fine grains, near their grain boundaries strong plastic strain gradients are formed and result in higher strain hardening rate in the N-50 HEA with a more heterogeneous structure; a higher strain hardening rate can stabilise the plastic deformation, thus improving the ductility of the N-50. In addition, introducing nitrogen atoms into alloys with FCC structure can promote rotation of grain orientation from the 〈011〉 to 〈111〉 direction due to the lattice expansion induced by the nitrogen incorporation in octahedral interstice (Templier et al 2010); therefore, texture is weakened in the N-50, which is also beneficial for the ductility (Lin et al 2016;Zhang et al 2019). Based on the above discussion, the nitrogen-doped HEA has a higher dislocation multiplication rate and more heterogeneous structure, resulting in the improvement of plastic deformation ability.…”

Effect of Heat Treatment on Microstructure and Tensile Properties of Ti-6Al-4V Alloy Produced by Coaxial Electron Beam Wire Feeding Additive Manufacturing

“…It has been widely understood that the mechanical properties of Ti-6Al-4V alloy fabricated by additive manufacturing are affected by its macro/ microstructure characteristics, which are sensitive to the fabrication process and post-heat treatment. As shown in previous studies, 6,7,13,[17][18][19][20][21] coarse columnar b grains (CGb) grow epitaxially along the<001> direction and result in anisotropy in the mechanical properties, i.e., outstanding strength with inferior ductility in the direction of travel, but superior ductility with low strength in the build direction. Post-heat treatment is expected to improve the mechanical properties.…”