【摘要】：Al-Zn-Mg-Cu系超高強(qiáng)鋁合金是航空航天和汽車制造等領(lǐng)域的關(guān)鍵結(jié)構(gòu)材料,提高合金強(qiáng)度、韌性,優(yōu)化合金抗腐蝕性是當(dāng)前超高強(qiáng)鋁合金的研究方向。晶粒分布狀態(tài)、析出相形式與鋁合金的性能密切相關(guān)。本文以超高強(qiáng)鋁合金Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr為試驗(yàn)材料,采用不同升溫速率退火至梯度溫度,探究合金在等速升溫退火過程中的微結(jié)構(gòu)演變。探索了熱塑性變形加工引起的不同初始形變儲能在不同升溫速率及固溶時間下對合金性能的影響。對合金進(jìn)行金相組織觀察、EBSD及XRD分析,硬度、電導(dǎo)率、拉伸性能測試,晶間腐蝕和剝落腐蝕試驗(yàn),檢測合金性能與微結(jié)構(gòu)變化。主要研究工作及取得的結(jié)論如下:(1)研究了快速升溫、慢速升溫退火至不同溫度對超高強(qiáng)鋁合金Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr擠壓材與熱壓材合金硬度、電導(dǎo)率與微結(jié)構(gòu)的影響。結(jié)果表明,升溫退火合金電導(dǎo)率隨著升溫截止溫度的增加先增大后減小,硬度先減小后增大。合金位錯在退火溫度達(dá)到300℃至450℃時降低為0,當(dāng)退火溫度達(dá)到470℃時,重新產(chǎn)生了位錯。合金在升溫退火至300℃晶粒平均尺寸略有降低,退火至470℃的合金晶粒尺寸顯著增大。熱壓材合金晶粒平均尺寸、低角度晶界比例較擠壓材得到明顯降低,位錯與晶界強(qiáng)化有所提升。(2)研究了快速、慢速升溫退火及2 h、24 h固溶時間對T6時效處理下高強(qiáng)鋁合金Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr擠壓材力學(xué)性能與微觀組織的影響。結(jié)果表明,慢速升溫退火能夠降低合金的晶粒尺寸,24 h固溶較2 h固溶能夠減少合金難溶第二相。合金硬度值在215.0 HV以上,導(dǎo)電率在25.0%IACS左右。慢速升溫2 h固溶、24 h固溶時效后合金試樣的屈服強(qiáng)度分別為647.9 MPa、697.1 MPa。強(qiáng)度的提升主要來自于固溶強(qiáng)化與時效沉淀析出相強(qiáng)化的總強(qiáng)化,其次為低角度晶界強(qiáng)化。合金晶間腐蝕等級為3級,固溶24 h合金抗剝落腐蝕性能較固溶2 h得到了輕微改善。(3)研究了初始形變儲能、退火升溫速率與固溶時間對T6時效處理下高強(qiáng)鋁合金Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr熱壓材力學(xué)性能與微觀組織的影響。結(jié)果表明,熱壓材合金平均晶粒尺寸較擠壓材合金顯著增大,慢速升溫較快速升溫合金晶粒平均尺寸得到降低,24 h固溶較2 h固溶合金晶粒平均尺寸有所降低。合金硬度、導(dǎo)電率與擠壓材變化不大,抗拉強(qiáng)度在700 MPa以上,屈服強(qiáng)度在670 MPa以上,延伸率在5.0%以上。慢速升溫能夠提高合金的強(qiáng)度及延伸率,在2 h固溶制度下,慢速升溫合金較快速升溫合金屈服強(qiáng)度由676.3 MPa增大至687.1 MPa,提高了10.8 MPa,延伸率由5.6%提高至7.2%,強(qiáng)度的提升主要來自于固溶強(qiáng)化和時效沉淀析出相強(qiáng)化。熱塑性變形加工在不損失合金強(qiáng)度的同時顯著提升合金的延伸率,24 h固溶較2 h固溶合金抗晶間腐蝕性能與抗剝落腐蝕性能明顯改善。
[Abstract]:Al-Zn-Mg-Cu-based ultra-high strength aluminum alloy is the key structural material in aerospace and automobile manufacturing. It is the research direction of ultra-high strength aluminum alloy to improve the strength and toughness of the alloy and optimize the corrosion resistance of the alloy. The distribution of grain and the form of precipitated phase are closely related to the properties of aluminum alloy. In this paper, the microstructure evolution of ultra-high strength aluminum alloy (Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr) during isothermal annealing was investigated by annealing from different heating rate to gradient temperature using ultra-high strength aluminum alloy as experimental material. The influence of different initial deformation energy storage rate and solution time on the properties of the alloy caused by thermoplastic deformation processing was investigated. Metallographic observation, EBSD and XRD analysis, hardness, conductivity, tensile properties, intergranular corrosion and peeling corrosion tests were carried out to detect the properties and microstructure changes of the alloys. The main research work and conclusions are as follows: (1) the hardness of ultra-high strength aluminum alloy Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr extruded material and hot pressed alloy was studied by fast heating, slow heating annealing to different temperature, and the hardness of superhigh strength aluminum alloy extruded material and hot pressed alloy was studied. The effect of electrical conductivity and microstructure. The results show that the electrical conductivity of the alloy increases at first and then decreases with the increase of the temperature cut-off temperature, and the hardness decreases first and then increases. The dislocation of the alloy decreases to 0 when the annealing temperature reaches 300 鈩，

本文編號：2438156