低层错能铜合金的强韧化研究

本项目首先进行铜合金的成分设计，研究加入不同合金元素对铜层错能的影响，得到低层错能铜合金。其次在液氮冷却的条件下对铜合金进行大塑性加工变形，得到超细晶粒，同时在超细晶粒内部产生纳米变形孪晶。最后将经过大塑性变形后的铜合金进行退火热处理，使合金在退火过程中形成纳米退火孪晶。通过这种方法制备的纳米孪晶铜合金将具有较稳定的微观组织、较高的强度、一定的塑性及良好的导电性能。拟解决如下问题：（1）纳米尺度的变形孪晶和退火孪晶形成机理与层错能的关系，层错能对孪晶层间距大小的影响；（2）塑性变形过程中，变形温度和应变速率等条件对晶粒大小、变形孪晶的尺寸等组织结构演变的影响；退火工艺对变形后材料的微观组织（主要是晶粒大小、变形孪晶）的影响，特别是对退火孪晶的形成规律进行深入研究；（3）研究孪晶界与位错之间的交互作用，从理论上解释孪晶对材料强度和塑性的影响，建立微观组织和力学性能、导电性能的定量关系。

The purpose of our research is mainly about the design of copper alloys, studying the influence of different alloying element upon stacking fault energy, in order to fabricate copper alloys with low stacking fault energy. Ultrafine grains can be introduced using severe plastic deformation in liquid nitrogen condition, with deformation nano-twins in the grains at the same time. Annealing treatment has been carried out after severe plastic deformation of copper alloys to form annealing twins during the annealing process. By this process, copper alloys can simultaneously have high strength and good ductility, stable microstructure and great electrical conductivity as well. We are going to solve problems as follows: (1) What is the relationship among the formation mechanism of deformation twins in nano scale and annealing twins and stacking fault energy, and also the influence of stacking fault energy upon the space of twin lamellae? (2) During the plastic deformation process, what are the influences of conditions like deformation temperature and strain rate upon the evolution of microstructure such as grain size and the size of deformation twins? The influence of annealing process upon microstructure after deformation will also be investigated, especially the formation mechanism of annealing twin, which will require deep discussion. (3) The interactions between twin boundaries and dislocations will also be studied, explaining the influence of twin on the strength and ductility of the materials. The quantitative relationships between the microstructure and mechanical properties and electrical conductivity will be built.