Institute of Materials, Shanghai University, Shanghai, 200444, China.
Zhejiang Institute of Advanced Materials, Shanghai University, Jiashan, 314100, China.
Adv Sci (Weinh). 2023 Apr;10(12):e2207535. doi: 10.1002/advs.202207535. Epub 2023 Feb 19.
Superplastic metals that exhibit exceptional ductility (>300%) are appealing for use in high-quality engineering components with complex shapes. However, the wide application of most superplastic alloys has been constrained due to their poor strength, the relatively long superplastic deformation period, and the complex and high-cost grain refinement processes. Here these issues are addressed by the coarse-grained superplasticity of high-strength lightweight medium entropy alloy (Ti V Zr Nb Mo , at.%) with a microstructure of ultrafine particles embedded in the body-centered-cubic matrix. The results demonstrate that the alloy reached a high coarse-grained superplasticity greater than ≈440% at a high strain rate of 10 s at 1173 K and with a gigapascal residual strength. A consecutively triggered deformation mechanism that sequences of dislocation slip, dynamic recrystallization, and grain boundary sliding in such alloy differs from conventional grain-boundary sliding in fine-grained materials. The present results open a pathway for highly efficient superplastic forming, broaden superplastic materials to the high-strength field, and guide the development of new alloys.
具有优异延展性（>300%）的超塑性金属在具有复杂形状的高质量工程部件中具有吸引力。然而，由于大多数超塑性合金的强度低、超塑变形周期相对较长以及晶粒细化工艺复杂且成本高，其广泛应用受到限制。这里通过高强度轻量中熵合金（TiVZrNbMo，at.%）的粗晶超塑性解决了这些问题，其微观结构为体心立方基体中嵌入的超细颗粒。结果表明，该合金在 1173 K 下应变率为 10 s 时达到了大于 ≈440%的高粗晶超塑性，且剩余强度为千兆帕斯卡。这种合金的连续触发变形机制与细晶材料中的传统晶界滑动不同，包括位错滑移、动态再结晶和晶界滑动的序列。目前的结果为高效超塑成形开辟了道路，将超塑性材料扩展到高强度领域，并指导新合金的开发。
