Al-7.5Zn-1.65Mg-1.4Cu-0.12Zr合金
(北京有色金屬研究總院 有色金屬材料制備加工國(guó)家重點(diǎn)實(shí)驗(yàn)室，北京 100088)
摘 要: 利用傳統(tǒng)技術(shù)制備新型高強(qiáng)韌低淬火敏感性的Al-7.5Zn-1.65Mg-1.4Cu-0.12Zr合金，研究合金在制備加工以及不同熱處理狀態(tài)下的微觀組織和性能。結(jié)果表明：該新型合金鑄態(tài)組織具有枝晶間非平衡共晶相AlZnMgCu相對(duì)較少的特點(diǎn)，經(jīng)過(guò)(440 ℃, 12 h)+(475 ℃, 24 h)雙級(jí)均勻化處理、擠壓變形和(475 ℃, 50~120 min)固溶處理后，組織均勻，固溶充分，除彌散分布的Al3Zr粒子外，僅殘留有少量的Al7Cu2Fe相顆粒；經(jīng)過(guò)單級(jí)、雙級(jí)和三級(jí)時(shí)效處理，合金可以獲得比較理想的組織和性能：T6態(tài)合金的抗拉強(qiáng)度590 MPa，電導(dǎo)率20.4 MS/m；經(jīng)T7雙級(jí)時(shí)效處理后，合金的抗拉強(qiáng)度、屈服強(qiáng)度、斷后伸長(zhǎng)率和電導(dǎo)率分別達(dá)到500~550 MPa、460~520 MPa、 17.0%~17.3%和23.4~25.0 MS/m；經(jīng)三級(jí)時(shí)效處理后，合金的組織和力學(xué)性能兼顧了T6和T7兩種制度的優(yōu)勢(shì)，與T6狀態(tài)相比，在抗拉強(qiáng)度僅降低3%的情況下，電導(dǎo)率顯著增加至23.1 MS/m；合金具有低的淬火敏感性，室溫水端淬試驗(yàn)測(cè)得的淬透深度可以達(dá)到120 mm以上；新型合金具有優(yōu)異的室溫?cái)嗔秧g性，其T6態(tài)的KIC值明顯高于本研究同時(shí)制備的7150合金。
關(guān)鍵字: 高強(qiáng)韌鋁合金；淬火敏感性；顯微組織；性能
high strength high toughness and low quench sensitivity
（State Key Laboratory for Fabrication and Processing of Non-ferrous Metals,
General Research Institute for Non-ferrous Metals, Beijing 100088, China）
Abstract:A novel Al-7.5Zn-1.65Mg-1.4Cu-0.12Zr alloy with high strength high toughness and low quench sensitivity was prepared by conventional ingot metallurgy. The microstructure and properties of the novel alloy under different processing and temper conditions were investigated. The results indicate that there are less coarse non-equilibrium AlZnMgCu phases in the as-cast alloy. After two-step homogenization (440 ℃, 12h+475 ℃, 24h) followed by hot extrusion and solid-solution treatment at 475 ℃ for 50−120 min, the microstructure of the novel alloy is homogeneous with few undissolved phases existing in the matrix except a few indissolvable Al7Cu2Fe particles and dispersed Al3Zr phases. When one-step aging, two-step aging and three-step aging are performed, optimum microstructure and properties of the novel alloy are obtained. When T6 temper is performed, the ultimate tensile strength (UTS) and electrical conductivity values are 590 MPa and 20.4 MS/m, respectively. After T7 temper treatment, the UTS, tensile yield strength (TYS), elongation and electrical conductivity values are 500−550 MPa, 460−520 MPa, 17.0%−17.3% and 23.4−25.0 MS/m, respectively. When three-step aging are performed, the alloy can obtain a good combination with T6 and T7 temper, the electrical conductivity is increased up to 23.1 MS/m and the UTS values is decreased only by 3% while in comparison with T6 temper. The novel alloy has low quench sensitivity, the quench sensitivity value of the alloy can reach more than 120 mm from the quenching end. The novel alloy also has better fracture toughness with higher KIC values than that of the 7150 alloy inT6 temper prepared by the same processing.
Key words: high strength high toughness Al alloy; quench sensitivity; microstructure; properties
