Cu对高强6000系铝合金峰时效析出相和性能的影响

Effect of Cu on Microstructure and Intergranular Corrosion Properties of High Strength 6000 Series Aluminum Alloy

摘要:

通过OM、TEM、HRTEM、室温拉伸和晶间腐蚀实验研究了Cu对高强6000系铝合金峰时效态析出相、拉伸性能和晶间腐蚀性能的影响。结果表明，添加Cu促进了合金峰时效态析出相的析出，随着Cu含量从0增加到0.18wt%和0.37wt%，峰时效态合金的析出相尺寸明显减小，体积分数从4.05%提升到4.61%和5.36%，对应合金的强度从421 MPa提高到448和459 MPa；结合HRTEM发现3种合金峰时效态的主要析出相为β″相，其中添加0.37wt%Cu的合金中还发现了L相。添加0.18wt%Cu对合金的耐晶间腐蚀性能有改善作用，而0.37wt%Cu的添加则降低了合金的耐晶间腐蚀性能。通过对合金晶内及晶界析出相的研究，发现0.18wt%Cu的添加促进了晶内强化β″相的析出，细化了晶界处无沉淀析出带（precipitation free zones, PFZ）的宽度，PFZ宽度为51.92 nm；0.37wt%Cu的添加促进了强化相的析出，同时改变了析出相类型，此外还发现0.37wt%Cu的添加显著粗化了晶界处无沉淀析出带的宽度，PFZ宽度为60.20 nm。结合时效析出相、拉伸强度和耐晶间腐蚀性能，发现0.18wt%Cu合金具有优良的综合性能。

Abstract:

The effects of Cu on the peak aging precipitates, tensile properties and intergranular corrosion properties of 6000 series aluminum alloy were investigated by OM, TEM, HRTEM, tensile and intergranular corrosion tests. The results show that the addition of Cu promotes the precipitation of the peak aging phase of the alloy. With the Cu content increasing from 0wt% to 0.18wt% and 0.37wt%, the precipitate size of the peak-aged alloy decreases significantly, the volume fraction increases from 4.05% to 4.61% and 5.36%, and strength increases from 421 MPa to 448 and 459 MPa, respectively. According to HRTEM analysis, the main precipitates of the three alloys in peak aging state is β" phase, and L phase is also found in the alloy with 0.37wt% Cu. The addition of 0.18wt% Cu improves the intergranular corrosion resistance of the alloy, while the addition of 0.37wt% Cu decreases the intergranular corrosion resistance of the alloy. It is found that the addition of 0.18wt% Cu promotes the precipitation of β" phase in the alloy, and the width of the precipitation free zone (PFZ) at the grain boundary is refined to 51.92 nm. The addition of 0.37wt% Cu promotes the precipitation of the strengthened phase and changes the type of the precipitated phase. In addition, it is found that the addition of 0.37wt% Cu significantly increases the width of the PFZ at the grain boundary, and the PFZ width is 60.20 nm. Combined with aging precipitates, tensile strength and intergranular corrosion, it is found that the alloy with 0.18wt% Cu has excellent comprehensive properties.