Metastable β-Ti alloys are attractive for additive manufacturing as they offer high strength and toughness, with the ability to readily tailor properties through control of the phase fraction and morphology of precipitate phases. However, during additive manufacturing processes thermal cycling associated with repetitive layer-by-layer deposition can potentially promote unintended β-phase decomposition and in-situ precipitation of other phases. This work investigates the stability of the β-phase during high heat input (1648 J/mm) Wire Arc Additive Manufacturing (WAAM) of Ti–3Al–8V–6Cr–4Mo–4Zr (Beta-C). Thermocouples and pyrometers to first used to measure the thermal environment during WAAM, and SEM, XRD and TEM characterisation techniques are used to investigate the microstructure of the as-built alloy. Despite observing large thermal excursions during WAAM well above the temperatures necessary to precipitate α-phase, no evidence of β-phase decomposition was found during WAAM. A Time-Temperature-Transformation (TTT) diagram is used to show that the cooling rates are too fast and the cumulative thermal exposures are too short to decompose the β-phase during WAAM. Consequently, the alloy retains the bcc β-phase which gives the alloy moderate strength (tensile strength ~748 MPa) and good ductility (~20%) during WAAM.

亚稳态β-Ti合金具有高强度和韧性，并具有通过控制相分数和析出相形貌来轻松调整其性能的能力，因此对增材制造具有吸引力。但是，在增材制造过程中，与重复的逐层沉积相关的热循环可能会促进意外的β相分解和其他相的原位沉淀。这项工作研究了Ti–3Al–8V–6Cr–4Mo–4Zr（Beta-C）的高热量输入（1648 J / mm）电弧添加制造（WAAM）期间β相的稳定性。首先使用热电偶和高温计来测量WAAM期间的热环境，然后使用SEM，XRD和TEM表征技术研究铸态合金的微观结构。尽管在WAAM期间观察到很大的热偏移，该温度远高于析出α相所需的温度，但在WAAM期间未发现β相分解的迹象。时间-温度变换（TTT）图用于显示WAAM期间冷却速率太快且累积热暴露太短而无法分解β相。因此，该合金保留了bccβ相，在WAAM过程中赋予了该合金适度的强度（抗张强度〜748 MPa）和良好的延展性（〜20％）。