初始形变储能、升温速率和固溶保温时间对超高强铝合金Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0

发布时间：2019-03-11 09:02

【摘要】：Al-Zn-Mg-Cu系超高强铝合金是航空航天和汽车制造等领域的关键结构材料,提高合金强度、韧性,优化合金抗腐蚀性是当前超高强铝合金的研究方向。晶粒分布状态、析出相形式与铝合金的性能密切相关。本文以超高强铝合金Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr为试验材料,采用不同升温速率退火至梯度温度,探究合金在等速升温退火过程中的微结构演变。探索了热塑性变形加工引起的不同初始形变储能在不同升温速率及固溶时间下对合金性能的影响。对合金进行金相组织观察、EBSD及XRD分析,硬度、电导率、拉伸性能测试,晶间腐蚀和剥落腐蚀试验,检测合金性能与微结构变化。主要研究工作及取得的结论如下:(1)研究了快速升温、慢速升温退火至不同温度对超高强铝合金Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr挤压材与热压材合金硬度、电导率与微结构的影响。结果表明,升温退火合金电导率随着升温截止温度的增加先增大后减小,硬度先减小后增大。合金位错在退火温度达到300℃至450℃时降低为0,当退火温度达到470℃时,重新产生了位错。合金在升温退火至300℃晶粒平均尺寸略有降低,退火至470℃的合金晶粒尺寸显著增大。热压材合金晶粒平均尺寸、低角度晶界比例较挤压材得到明显降低,位错与晶界强化有所提升。(2)研究了快速、慢速升温退火及2 h、24 h固溶时间对T6时效处理下高强铝合金Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr挤压材力学性能与微观组织的影响。结果表明,慢速升温退火能够降低合金的晶粒尺寸,24 h固溶较2 h固溶能够减少合金难溶第二相。合金硬度值在215.0 HV以上,导电率在25.0%IACS左右。慢速升温2 h固溶、24 h固溶时效后合金试样的屈服强度分别为647.9 MPa、697.1 MPa。强度的提升主要来自于固溶强化与时效沉淀析出相强化的总强化,其次为低角度晶界强化。合金晶间腐蚀等级为3级,固溶24 h合金抗剥落腐蚀性能较固溶2 h得到了轻微改善。(3)研究了初始形变储能、退火升温速率与固溶时间对T6时效处理下高强铝合金Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr热压材力学性能与微观组织的影响。结果表明,热压材合金平均晶粒尺寸较挤压材合金显著增大,慢速升温较快速升温合金晶粒平均尺寸得到降低,24 h固溶较2 h固溶合金晶粒平均尺寸有所降低。合金硬度、导电率与挤压材变化不大,抗拉强度在700 MPa以上,屈服强度在670 MPa以上,延伸率在5.0%以上。慢速升温能够提高合金的强度及延伸率,在2 h固溶制度下,慢速升温合金较快速升温合金屈服强度由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%,强度的提升主要来自于固溶强化和时效沉淀析出相强化。热塑性变形加工在不损失合金强度的同时显著提升合金的延伸率,24 h固溶较2 h固溶合金抗晶间腐蚀性能与抗剥落腐蚀性能明显改善。
[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，

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