Achieving ultra-high strength rapidly in Ti-3Al-8V-6Cr-4Mo-4Zr alloy processed by directed energy deposition

Kun Zhang, Wen Hao Kan, Yuman Zhu, Samuel Chao Voon Lim, Xiang Gao, Chun Kit Sit, Chunguang Bai, Aijun Huang

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This work investigates the viability of fabricating Ti-3Al-8V-6Cr-4Mo-4Zr (Beta-CTM) using laser-based and powder-fed directed energy deposition. To determine an appropriate ageing strategy, heat treatments were conducted at 440 °C and 480 °C over different periods of time and their effectiveness were determined through hardness testing. After identifying an optimal ageing treatment, tensile properties were investigated on the samples in the as-built and aged conditions. The microstructure, hardness and tensile properties of the as-built sample was found to resemble that of a conventionally-manufactured and solution-treated alloy. However, as compared to conventionally-manufactured Ti-3Al-8V-6Cr-4Mo-4Zr subjected to the same ageing temperature, the ageing process was much quicker with the DED-processed alloy because of its high dislocation density. Furthermore, the latter can also achieve much higher strength while also having comparable ductility. To achieve a similar ageing response and tensile behavior, conventionally-manufactured Ti-3Al-8V-6Cr-4Mo-4Zr would require cold-working prior to ageing. Carbon additions were also investigated to further accelerate the ageing response and to refine the β grain size. While the ageing response was much quicker and a much harder alloy can be produced, the carbon amount added was insufficient for β grain refinement, which resulted in reduced ductility without a change in strength.

Original languageEnglish
Article number111325
Number of pages12
JournalMaterials & Design
Publication statusPublished - Dec 2022


  • Ageing
  • Beta-C
  • Direct energy deposition
  • Tensile properties
  • Titanium

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