连续柱状多晶铜室温强塑性变形过程中的微观组织演变和性能

Microstructure Evolution and Properties of Continuous Columnar-Grained Polycrystalline Copper During Intense Plastic Deformation Process at Room Temperature

摘要:

利用光学显微镜、扫描电子显微镜、维氏显微硬度计和万能拉伸试验机，定量研究了连续柱状多晶铜在室温下强塑性拉拔变形过程中的组织演变和性能变化规律，并根据高分辨率电子背散射衍射技术测量的不同织构中位错胞的结构参数计算了形变储能。结果表明，连续柱状晶组织逐步细化为纤维晶组织，铸态连续柱状多晶铜的抗拉伸强度为168 MPa，延伸率为52%，导电率达到103%IACS。室温连续拉拔变形达到99%时，抗拉伸强度增加至455 MPa，延伸率下降至3%，导电率降低至96.8%IACS；连续柱状多晶铜的横截面和纵截面均具有<001>原始择优取向，且随着拉拔变形量的增加，最终形成大量的<111>取向+少量的<001>取向纤维织构。横截面中Cube织构逐渐减少，S织构和Copper织构逐渐增加，而纵截面中Cube织构和Goss织构逐渐向Brass织构、Copper织构和S织构转变。晶界和变形带处的核平均误差（KAM）值较高，且随着变形量的增加，KAM值逐渐增大，应力更集中。相同变形量下，横截面比纵截面具有更高的形变储能，<001>取向织构组分具有比<111>取向织构组分更低的形变储能。在大变形量加工之后，连续柱状多晶铜仍具有高含量的“软”取向<001>形变织构，是其具有低加工硬化率和优异的冷变形能力的重要原因。

Abstract:

The microstructure evolution and properties of continuous columnar-grained (CCG) polycrystalline copper during intense drawing deformation at room temperature were investigated by optical microscope, scanning electron microscope, Vickers microhardness tester, and universal tensile testing machine. The stored energy was calculated according to the structural parameters of dislocation cells in different textures based on high-resolution electron backscattered diffraction. Results show that CCG microstructure is gradually thinned into fibrous tissue. The as-cast CCG polycrystalline copper has tensile strength of 168 MPa, elongation of 52%, and conductivity of 103%IACS. After the drawing deformation of 99% at room temperature, the tensile strength of CCG polycrystalline copper increases to 455 MPa. However, the elongation reduces to 3%, and the conductivity decreases 96.8%IACS. Both the transverse and longitudinal sections of CCG polycrystalline copper have <001> original preferred orientation. A large number of fiber textures of <111> orientation and a small number of fiber textures of <001> orientation are formed with increasing the drawing deformation amount. Cube texture of the transverse section gradually decreases, and S texture and Copper texture gradually increase. Meanwhile, the Cube texture and Goss texture of longitudinal section are gradually transformed into Brass texture, Copper texture, and S texture. The kernel average misorientation (KAM) value at grain boundaries and in the deformation bands is large. Additionally, with increasing the deformation amount, KAM value is gradually increased and the stress is more concentrated. Under the same deformation conditions, the transverse section has higher stored energy than the longitudinal section does, and <001> orientation fiber texture has lower stored energy than <111> orientation fiber texture does. After the strong plastic deformation, CCG polycrystalline copper still has a large number of deformation textures with “soft” <001> orientation, which is an important reason for its low work hardening rate and excellent cold deformation ability.