Abstract The aim of the present work was to study the influence of Gd microaddition on the sequence and temperatures of phase transformations as well as on the microstructural evolution and properties of a new six-component TiAl-based alloy Ti-44.5Al-2V-1Nb-xZr/yCr-(0 … 0.1)Gd (at.%) with variable Zr (x = 0.5–1.5 at.%; eq. 1.2–3.5 wt%) and Cr (y = 1.5–2.5 at.%; eq. 2.0–3.5 wt%) content in the as-cast condition using thermodynamic calculations in Thermo-Calc software and experimental methods including differential scanning calorimetry, in-situ high-temperature X-ray diffraction analysis, optical, scanning, and high-resolution transmission microscopy. It was demonstrated that in all compositions of the studied alloy the sequence of phase transformations at high temperature interval includes L→β, β→α, and α→γ transformations, passing through the single-phase β and α fields. These are then followed by a three-phase eutectoid reaction α→α2+γ in Zr-containing compositions and further by a four-phase α→α2+γ+β reaction in Cr- and (Zr+Сr)-containing compositions. It has been revealed that the addition of 0.1 at.% Gd does not change the sequence and temperatures of these phase transformations. Nevertheless, the formation of nano-particles, identified as base-centered monoclinic Gd2O3 oxide located in Zr-containing compositions inside the γ lamellae and in Cr- and (Zr + Cr)-containing compositions on the boundaries of the γ lamellae and inside the β phase interlayers and being coherent with the β0 phase, results in reduction of (α2+γ) colony size in the as-cast condition (VAR + VAR + VIM) down to 100 ± 10 μm. It has been also found that ultimate tensile strength and plastic elongation in Zr- and Cr-containing compositions of the studied alloy in the as-cast condition measured at room temperature are 473 ± 8 MPa, 1.1 ± 0.1% and 513 ± 10 MPa, 1.4 ± 0.1%, respectively. The addition of 0.1 at.% Gd results in plastic elongation increasing to (1.3–1.6)±0.1%, while remaining the strength unaffected.

中文翻译：

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Gd添加对Zr和Cr含量变化的β凝固TiAl基合金的相组成、结构和性能的影响

摘要 本工作的目的是研究 Gd 微添加对新型六组分 TiAl 基合金 Ti-44.5Al-2V-1Nb 的相变顺序和温度以及显微组织演变和性能的影响。 -xZr/yCr-(0 … 0.1)Gd (at.%) 与可变 Zr (x = 0.5–1.5 at.%; eq. 1.2–3.5 wt%) 和 Cr (y = 1.5–2.5 at.%; eq . 2.0–3.5 wt%) 在铸态条件下的含量，使用 Thermo-Calc 软件中的热力学计算和实验方法，包括差示扫描量热法、原位高温 X 射线衍射分析、光学、扫描和高分辨率透射显微镜。结果表明，在所研究合金的所有成分中，高温区间的相变序列包括 L→β、β→α 和 α→γ 相变，通过单相 β 和 α 场。然后在含 Zr 的组合物中进行三相共析反应 α→α2+γ，并进一步在含 Cr 和 (Zr+Сr) 的组合物中进行四相 α→α2+γ+β 反应。已经表明，添加 0.1 at.% Gd 不会改变这些相变的顺序和温度。然而，纳米粒子的形成，被确定为位于 γ 片晶内部的含 Zr 组合物中以及 γ 片晶边界上和内部的含 Cr 和 (Zr + Cr) 组合物中的碱中心单斜 Gd2O3 氧化物。 β 相夹层并与 β0 相相干，导致铸态条件 (VAR + VAR + VIM) 中的 (α2+γ) 菌落尺寸减小至 100 ± 10 μm。还发现，在室温下测量的铸态条件下所研究合金的含 Zr 和 Cr 组合物中的极限拉伸强度和塑性伸长率为 473 ± 8 MPa、1.1 ± 0.1% 和 513 ± 10 MPa，分别为 1.4 ± 0.1%。添加 0.1 at.% Gd 导致塑性伸长率增加到 (1.3–1.6)±0.1%，同时保持强度不受影响。