【作者】 李晓峰；

【导师】 孟亮；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2011， 硕士

【摘要】 本文采用冷变形结合中间热处理方法制备了不同Zr及Mg元素含量的Cu-0.4wt.%Cr-0.02 wt.%Si合金,通过研究不同元素含量的Cu-0.4 wt.%Cr-0.02 wt.%Si合金在不同变形量下的组织形态、强度以及电导率,分析了Zr、Mg元素对合金力学性能和电学性能的影响,进而优化合金成分。在此基础上,进一步对比不同热处理工艺参数对合金组织以及性能的影响,进一步优化合金的热处理工艺。选取最优成分采用最优热处理工艺研究了冷拉拔对Cu-0.4 wt.%Cr-0.12 wt.%Zr-0.02 wt.%Si-0.05 wt.% Mg合金组织性能的影响以及合金强变形下的热稳定性,探讨了合金的强度、位错密度以及储存能三者之间的关系。四种试验合金的抗拉强度均随变形程度的增加而增加,添加Zr元素的合金抗拉强度始终高于不含Zr元素的合金,且强度上升幅度比较大。Mg元素也表现出一定的强化作用,但强化效果低于Zr元素。随变形量增加,四种合金的相对电导率大致呈下降趋势。Zr元素对合金电导率的损害作用随变形量的增加而增加,在η=6.1时,可使电导率下降约7.2 %IACS.Mg元素对相对电导率的影响比较稳定,并没有随变形量的增加有明显的改变,基本使电导率波动幅度在(2-3)%IACS.将η=1.8的四种试验合金在500℃进行等温退火处理,四种试验合金的显微硬度均随退火时间的延长先增大而后减小并在经过1 h退火处理后达到峰值,添加Zr元素的合金显微硬度始终高于不含Zr元素的合金,且硬度下降的幅度小于不含Zr元素的合金。四种试验合金的相对电导率均随退火时间延长先剧烈增加而后缓慢增加,且均在经过1h退火处理后增加的幅度达到最大值。在拉拔应变比小于6.7范围内,随着变形程度的增加,Cu-0.4 wt.%Cr-0.12 wt.%Zr-0.02 wt.%Si-0.05 wt.%Mg合金晶粒逐渐细化,纤维状晶粒的最小晶粒尺寸约为490 nm.晶体取向逐渐背离完全退火态晶体取向,并逐渐形成<111>织构。合金的屈服强度、微应变、位错密度以及储存能随变形量增加而增加。通过热分析,计算了不同变形量合金的储存能并进一步估算合金的位错密度和屈服强度。合金储存能的释放主要是由于位错密度的降低。当变形量6.7≤η≤7.4时,Cu晶粒会有一定程度的粗化同时对应着屈服强度、位错密度、微应变和储存能的降低,这说明Cu-0.4 wt.%Cr-0.12 wt.%Zr-0.02 wt.%Si-0.05 wt.%Mg合金在这此变形程度下发生动态回复再结晶。将Cu-0.4 wt.%Cr-0.12 wt.%Zr-0.02 wt.%Si-0.05 wt.%Mg合金在不同温度下退火1 h,随着退火温度升高,纤维状的Cu晶粒逐渐被粗大的等轴晶替代。在这一过程中,硬度、微应变、屈服强度和电阻率逐渐下降。随着退火温度升高,拉拔态合金晶体取向逐渐接近完全退火态晶体取向,纵横截面硬度差值逐渐降低。储存能的释放主要由于位错密度降低,合金主要的强化机制为位错强化。更多还原

【Abstract】 Cu-0.4 wt.%Cr-0.02 wt.%Si alloys with different contents of Zr and Mg elements were prepared by casting, heat treating and cold drawing. The drawn microstructure of the alloys was investigated at different drawing ratios. The effects of Zr and Mg elements on the microstructure, mechanical and electrical properties during drawing deformation were discussed, and the alloy composition was suitably selected. Meanwhile, the effects of intermediate heat treatments on microstructure and properties were also studied in order to improve the heat treatment process. In these alloys, Cu-0.4 wt.% Cr-0.12 wt.% Zr-0.02 wt.% Si-0.05 wt.% Mg alloy showed a more excellent match between strength and conductivity. The cold drawing behaviour and the thermal stability of Cu-0.4 wt.% Cr-0.12 wt.% Zr-0.02 wt.% Si-0.05 wt.% Mg alloy were investigated. The relationship between the stored energy and flow stress which are connected by dislocation density has been discussed.The tensile strength of the four test alloys increases with extended plastic deformation and the tensile strength of adding Zr element alloy is always higher than that of non-Zr alloys. Mg element also shows some strengthening effect, but the effect of Mg element on the strengthening is lower than Zr element. As drawing deformation increases, the relative conductivity of the four alloys generally decreases. Zr addition shows a more significant negative effect on the electrical conductivity of the alloys at higher drawing ratios and the conductivity can drop by about 7.2% IACS withη=6.1. Mg addition maintains a basically constant effect on the electrical conductivity of the alloys at different drawing ratios and the conductivity fluctuations is about 2～3% IACS.With annealing time extending, the hardness of the four test alloys increases first and then decreases, reaching their peak values after annealing treatments at 500℃for 1 hour. The hardness of Zr containing element alloy is always higher than that of Zr free element alloy. The relative conductivity of the four test alloy increases sharply and then slowly with increasing annealing time and reaches their peak values after 1 hour annealing treatments.Cold drawing was conducted at room temperature to impose high strain into Cu-0.4 wt.%Cr-0.12 wt.%Zr-0.02 wt.%Si-0.05 wt.%Mg. An increasing cold drawing strain leads to a sharply decrease in filament size at first and then a saturation value of～490 nm. The crystal orientation is deviating from the as-cast specimens and<111> texture is gradually formed. The flow stress, microstrain, dislocation density and stored energy are gradually increasing beforeη= 6.7. The thermal analysis was carried out for the alloy at different draw ratios. The stored energy was calculated and utilized to estimate the dislocation density and the flow stress. It was found that the stored energy increases with the draw ratio rising until a peak is reached withη=6.7. The release of stored energy is primarily due to the decrease of dislocation density. The dynamic recovery has taken place as 6.7<η≤7.4, which is confirmed by the change of the crystal orientation, microstrain, stored energy, flow stress and dislocation density.The Cu-0.4 wt.% Cr-0.12 wt.% Zr-0.02 wt.% Si-0.05 wt.% Mg alloy was drawn toη=6.0 and annealed at different temperatures. With the annealing temperature increasing, the ribbonlike Cu crystals are gradually replaced by gross equiaxed grains, resulting in the reduction in hardness, flow stress and electrical resistivity. The crystal orientation of as-draw specimen is gradually approaching that of full annealed specimen and the hardness difference between longitudinal and transverse directions decreases as annealing temperature increasing. The release of stored energy and the reduction of resistivity are primarily due to the decrease of dislocation density. The main strengthening effect is attributed to dislocation mechanism in Cu-0.4 wt.%Cr-0.12 wt.%Zr-0.02 wt.%Si-0.05 wt.%Mg alloy.更多还原