(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083；
2. 中南大學(xué) 材料微結(jié)構(gòu)研究所，長(zhǎng)沙 410083；
3. 中南大學(xué) 有色金屬先進(jìn)結(jié)構(gòu)材料與制造協(xié)同創(chuàng)新中心，長(zhǎng)沙 410083)
摘 要: 對(duì)高層錯(cuò)能的純Cu和低層錯(cuò)能的Cu-30%Zn(質(zhì)量分?jǐn)?shù))合金進(jìn)行室溫多向壓縮變形及退火實(shí)驗(yàn)，并利用OM、SEM/EBSD、TEM技術(shù)及電子萬能試驗(yàn)機(jī)對(duì)其在變形和退火過程中的晶粒細(xì)化情況和不同累積變形量(Σε)后的拉伸力學(xué)性能進(jìn)行觀察和分析。結(jié)果表明：在多向壓縮過程中，隨著層錯(cuò)能的降低，銅合金的晶粒細(xì)化機(jī)制由傳統(tǒng)的連續(xù)動(dòng)態(tài)再結(jié)晶(cDRX)細(xì)化機(jī)制轉(zhuǎn)變成孿晶分割晶粒細(xì)化機(jī)制。在變形過程中，兩者的真應(yīng)力-累積應(yīng)變(σ-Σε)曲線呈現(xiàn)穩(wěn)態(tài)流變特征；當(dāng)Σε＞2.4后，層錯(cuò)能較低的Cu-30%Zn合金仍存在緩慢的加工硬化，而純Cu僅在Σε＜2.4階段存在加工硬化。隨著Σε的增大，層錯(cuò)能較低的Cu-30%Zn合金晶粒細(xì)化比純Cu的更加明顯：當(dāng)Σε=2.4時(shí)，Cu-30%Zn合金內(nèi)部基本為細(xì)小的晶粒，這是由其內(nèi)部的孿晶交叉、分割晶粒而形成；而純Cu僅在局部出現(xiàn)細(xì)晶。隨著Σε的增大，Cu-30%Zn合金內(nèi)部的畸變程度以及變形后的強(qiáng)度也遠(yuǎn)大于純Cu的。經(jīng)Σε=2.4多向壓縮變形后，在退火過程中，層錯(cuò)能較低的Cu-30%Zn合金再結(jié)晶晶粒明顯比純Cu細(xì)小，這是由于其內(nèi)部層錯(cuò)密度較大，再結(jié)晶形核點(diǎn)較多所致。
關(guān)鍵字: 銅合金；層錯(cuò)能；晶粒細(xì)化；孿晶；再結(jié)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
