时效析出物与层状非均质结构协同作用下Cu–Be/Cu复合材料强韧化机理研究

After aging treatment, the ultimate tensile strength of high strength beryllium copper alloy can reach 1400 MPa but the elongation is less than 5%. The significant strength and ductility/toughness trade-off presented in the beryllium copper alloy seriously affects the safety and reliability during the service. In this work, the method of lamellar heterogeneous architecture is applied to beryllium copper materials. The high ductility and toughness of pure Cu together with the high strength of Cu–Be alloy will be utilized to obtain Cu–Be/Cu composite possessing high strength and ductility simultaneously. The accumulative rolling bonding and consequent heat treatment processes will be used to prepare lamellar heterogeneous Cu–Be/Cu composite with periodic fluctuations in grain size. The correlation of the lamellar heterogeneous architecture parameters and the strength and ductility/toughness of the composite will be studied systematically, as well as the relationship between the precipitation characters and the strength and ductility/toughness. Though the investigation of the strain hardening behavior of composite under the synergistic effect of the precipitation and lamellar heterogeneous architecture, the quantitative analysis model between the microstructure parameters and stress-strain behavior can be established. Subsequently, the model will be utilized to reveal the synergistic mechanism between the precipitation and lamellar heterogeneous architecture. Finally, the general design principle of the optimal matching between the precipitation and lamellar heterogeneous architecture can be obtained, which will provide new suggestions for solving the problem of significant strength and ductility/toughness trade-off in the precipitation strengthening alloy.

高铍含量的铍铜（Cu–Be）合金时效后抗拉强度可达1400MPa以上，而伸长率不到5%，呈现显著的强度与塑性/韧性倒置关系，严重影响了合金服役的安全可靠性。本项目将层状非均质构型设计的思想运用于铍铜材料，充分利用纯铜的高塑性/韧性及Cu–Be合金的高强度，获得高强韧的Cu–Be/Cu复合材料，并在此基础上重点阐明层状非均质结构与时效析出物的协同作用机制。项目拟通过累积叠轧复合及后续热处理制备晶粒尺寸周期波动的层状非均质Cu–Be/Cu复合材料，分别研究构型参数及析出物特征对复合材料强韧性的影响规律；通过探索层状非均质结构及时效析出物协同作用下复合材料的应变硬化行为，建立复合材料微观组织参数与宏观应力-应变行为间的定量分析模型，揭示时效析出物与层状非均质结构的协同作用机制，获得析出物特征与层状非均质构型参数最优匹配的一般性设计原理，为解决析出强化合金显著的强度与塑性/韧性倒置关系提供新思路。

高铍含量的铍铜（Cu–Be）合金呈现显著的强度与塑性/韧性倒置关系，严重影响了合金服役的安全可靠性。本项目将层状非均质构型设计的思想运用于铍铜材料，充分利用纯铜的高塑性/韧性及Cu–Be合金的高强度，充分利用纯铜、黄铜的高塑性/韧性及Cu–Be合金的高强度，获得高强韧的Cu–Be/Cu及Cu–Be/Cu-Zn复合材料。项目通过真空热压复合、冷轧变形及后续热处理制备了具有不同构型参数（异种金属层厚比、硬度比等）的层状非均质复合材料，探索了构型参数对复合材料强韧性的影响规律。结果表明当Cu–Be层和Cu-Zn层之间的层厚比为5:1时，Cu-Be/Cu-Zn层状复合材料抗拉强度与相同热处理状态下的Cu-Be合金接近，但其均匀伸长率可达Cu-Be合金的3倍。这是由于层厚比为5:1时，Cu-Be/Cu-Zn界面间距与长程背应力的作用范围相匹配，异种金属层之间形成了更好地耦合，界面也可发挥更好的应变协调作用，界面附近堆积了更多的几何必须位错（GNDs），从而产生了更大的背应力强化，显著提升了层状复合材料的应变硬化能力，因此获得了具有高强韧性的材料。对异种金属硬度比不同的Cu–Be/Cu层状非均质复合材料的研究表明，随着Cu–Be层析出强化效果的增加，材料的强韧性先增加后降低，当Cu–Be层与Cu层之间的硬度比为5:1时，层状复合材料强韧性最好；过高的硬度比会导致不同金属层间的变形不协调性大幅增加，使得金属层间界面的应变协调作用降低，从而导致材料强韧性下降。本项目阐明了层状非均质结构复合材料的应变硬化行为，揭示了时效析出物与层状非均质结构协同作用下复合材料的强韧化机理，为解决析出强化合金显著的强度与塑性/韧性倒置关系提供了新思路。