(1. 西安交通大學 材料科學與工程學院，西安 710049；
2. 西安交通大學 金屬材料強度國家重點實驗室，西安 710049)
摘 要: 利用電導率、顯微硬度和宏觀拉伸測試，結(jié)合SEM、TEM、APT和XRD等表征手段對Al-Zn-Mg合金中的團簇長大動力學以及團簇對合金變形斷裂的影響進行了研究。結(jié)果表明：Al-Zn-Mg合金經(jīng)過約1000 h自然時效進入穩(wěn)定狀態(tài)，基體中形成了超高密度的Mg-Zn團簇，材料得到有效強化；人工時效態(tài)Al-Zn-Mg合金中析出相隨高溫時效時間的延長發(fā)生長大，類型以亞穩(wěn)η′與穩(wěn)定η相為主，部分析出相逐漸不可被位錯切過。T6/T7態(tài)合金小應變下可迅速形成大量位錯引起材料強化，但在大應變時會發(fā)生劇烈的動態(tài)回復，造成其較弱的加工硬化能力與較低的均勻伸長率(約13%)；而在T4態(tài)Al-Zn-Mg合金中，團簇和溶質(zhì)原子的存在能有效抑制動態(tài)回復，并可在變形時伴生動態(tài)應變時效效應，造成材料較強的加工硬化和更優(yōu)的均勻延伸性能(約25%)。
關(guān)鍵字: Al-Zn-Mg系鋁合金；溶質(zhì)原子團簇；三維原子探針；長大動力學；加工硬化
（1. School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China;
2. State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China）
Abstract:The clusters growth kinetics and the deformation properties in natural-aged Al-Zn-Mg alloy were investigated by electrical conductivity, microhardness and tensile tests. Multiple characterization methods including SEM, TEM, APT and XRD were applied to reveal the microstructure features. The results show that through the natural aging of about 1000 h, the high number density of solute clusters forms in 7B05 alloy and are responsible for the natural aging hardening effect. Natural-aged Al-Zn-Mg alloy exhibits better strain-hardening properties and uniform elongation than their thermally treated counterparts. The presence of shearing-resistant precipitates in thermal-treated alloys results in rapid accumulation of dislocation loops around precipitates at small strain whereas at large strain, the dislocation dynamic recovery process is dominant. In natural-aged Al-Zn-Mg alloy, the dislocation recovery is inhibited by solutes and clusters, meanwhile, the dynamic strain aging effect raises the resistance of dislocation movements, both leading to a greater strain-hardening capability.
Key words: Al-Zn-Mg alloy; solute atom clusters; atom probe tomography; growth kinetics; strain-hardening properties
