(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 中南大学 材料微结构研究所，长沙 410083；
3. 中南大学 有色金属先进结构材料与制造协同创新中心，长沙 410083)
摘 要: 对高层错能的纯Cu和低层错能的Cu-30%Zn(质量分数)合金进行室温多向压缩变形及退火实验，并利用OM、SEM/EBSD、TEM技术及电子万能试验机对其在变形和退火过程中的晶粒细化情况和不同累积变形量(Σε)后的拉伸力学性能进行观察和分析。结果表明：在多向压缩过程中，随着层错能的降低，铜合金的晶粒细化机制由传统的连续动态再结晶(cDRX)细化机制转变成孪晶分割晶粒细化机制。在变形过程中，两者的真应力-累积应变(σ-Σε)曲线呈现稳态流变特征；当Σε＞2.4后，层错能较低的Cu-30%Zn合金仍存在缓慢的加工硬化，而纯Cu仅在Σε＜2.4阶段存在加工硬化。随着Σε的增大，层错能较低的Cu-30%Zn合金晶粒细化比纯Cu的更加明显：当Σε=2.4时，Cu-30%Zn合金内部基本为细小的晶粒，这是由其内部的孪晶交叉、分割晶粒而形成；而纯Cu仅在局部出现细晶。随着Σε的增大，Cu-30%Zn合金内部的畸变程度以及变形后的强度也远大于纯Cu的。经Σε=2.4多向压缩变形后，在退火过程中，层错能较低的Cu-30%Zn合金再结晶晶粒明显比纯Cu细小，这是由于其内部层错密度较大，再结晶形核点较多所致。
关键字: 铜合金；层错能；晶粒细化；孪晶；再结晶
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Institute for Materials Microstructure, Central South University, Changsha 410083, China;
3. Nonferrous Metal Oriented Advanced Structural Materials and
Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083, China）
Abstract:The high stack fault energy (SFE) pure Cu and low SFE Cu-30%Zn (mass fraction) alloy were deformed by multi-direction forge (MDF) at room temperature and subsequent annealed. The grain refinement during MDF deformation and subsequent annealing was observed by OM, SEM/EBSD and TEM techniques, and the tensile mechanical properties after MDF deformation of different cumulative strains (Σε) were measured by an Instron-type mechanical testing machine. The results show that, in the process of MDF, with the decrease of SFE, the grain refinement mechanism of Cu alloy changes from traditional continuous recrystallization (cDRX) refinement to twin segment refinement. In the process of MDF, true stress-cumulative strain (σ-Σε) curves of both materials present the characteristics of steady flow. When Σε＞2.4, Cu-30%Zn alloy with lower SFE is still hardening slowly, but pure Cu is only hardening in the period of Σε＜2.4. When Σε is increasing, grain refinement of Cu-30%Zn alloy with lower SFE is more evident than that of pure Cu: when Σε=2.4, almost all grains in Cu-30%Zn alloy are ultra-fined grains (UFGs), this is formed by the twins intersection and grain fragment of twins in it, while in pure Cu, UFGs are locally distributed. Moreover, the degree of distortion and tensile strength after MDF deformation of Cu-30%Zn alloy are much larger than those of pure Cu. After MDF deformation at Σε=2.4, the recrystallized grains in Cu-30%Zn alloy with lower SFE are much smaller than those in pure Cu during annealing because of the big defect density, like stack fault, and more nuclear sites for recrystallization in Cu-30%Zn alloy.
Key words: Cu alloy; stack fault energy; grain refinement; deformation twin; recrystallization
