Abstract High-alloyed superalloy U720Li is difficult to be processed through the conventional cast and wrought route. Boron is an important strengthening element for superalloys, but the role of boron in the hot ductility of U720Li alloy is not clear. This study is focused on the effect of boron addition, in the range of < 0.0005 wt%–0.0240 wt%, on the microstructure and hot ductility behavior of superalloy U720Li. It is found that boron addition significantly increases the content of eutectic (γ + γ′) and greatly affects the degree of continuity of the grain boundary eutectic (γ + γ′) precipitation. Boron addition dramatically worsens the 1100 °C tensile ductility of conventional cast U720Li alloy and causes a change in tensile fracture mode from transgranular to intergranular. The eutectic (γ + γ′) represents the most effective site for crack initiation. Boron deteriorates the hot ductility mainly by promoting the continuous precipitation of eutectic (γ + γ′) along the grain boundary. Graphic abstract

中文翻译：

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加硼镍基高温合金U720Li的组织和热延性行为

摘要 U720Li高合金高温合金难以通过常规的铸锻工艺进行加工。硼是高温合金的重要强化元素，但硼对U720Li合金热延展性的作用尚不清楚。本研究的重点是在 < 0.0005 wt%–0.0240 wt% 范围内添加硼对 U720Li 高温合金的微观结构和热延展性行为的影响。研究发现，硼的添加显着增加了共晶（γ+γ'）的含量，并且极大地影响了晶界共晶（γ+γ'）析出的连续性程度。硼的添加显着恶化了传统铸造 U720Li 合金的 1100 °C 拉伸延展性，并导致拉伸断裂模式从穿晶到晶间的变化。共晶 (γ + γ') 代表最有效的裂纹萌生位置。硼主要通过促进共晶（γ+γ'）沿晶界的连续析出来降低热延展性。图形摘要