(1. 西安交通大學(xué) 材料科學(xué)與工程學(xué)院，西安 710049；
2. 西安交通大學(xué) 金屬材料強(qiáng)度國家重點(diǎn)實(shí)驗(yàn)室，西安 710049)
摘 要: 利用電導(dǎo)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(tuán)簇長大動(dòng)力學(xué)以及團(tuán)簇對合金變形斷裂的影響進(jìn)行了研究。結(jié)果表明：Al-Zn-Mg合金經(jīng)過約1000 h自然時(shí)效進(jìn)入穩(wěn)定狀態(tài)，基體中形成了超高密度的Mg-Zn團(tuán)簇，材料得到有效強(qiáng)化；人工時(shí)效態(tài)Al-Zn-Mg合金中析出相隨高溫時(shí)效時(shí)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(cuò)切過。T6/T7態(tài)合金小應(yīng)變下可迅速形成大量位錯(cuò)引起材料強(qiáng)化，但在大應(yīng)變時(shí)會(huì)發(fā)生劇烈的動(dòng)態(tài)回復(fù)，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(tuán)簇和溶質(zhì)原子的存在能有效抑制動(dòng)態(tài)回復(fù)，并可在變形時(shí)伴生動(dòng)態(tài)應(yīng)變時(shí)效效應(yīng)，造成材料較強(qiáng)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(tuán)簇；三維原子探針；長大動(dòng)力學(xué)；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
