强塑性变形与热处理对Al-12.51Zn-2.85Mg-2.83Cu-0.18Zr-0.0598Sr合金组织性能的调控

发布时间：2018-03-31 09:04

  本文选题：超高强铝合金　切入点：ECAP　出处：《江苏大学》2017年硕士论文

【摘要】：7000系铝合金凭借其自身具备的密度小、比强度高、抗腐蚀性能好等优点被广泛应用在航空航天、武器制造、汽车船舶等制造业领域。本文以自主创新研制的超高强铝合金(wt.%)Al-12.51Zn-2.85Mg-2.83Cu-0.18Zr-0.0598Sr挤压材为试验材料,通过金相组织、Electron Backscattered Diffraction(EBSD)、X-ray diffraction(XRD)、显微硬度、电导率、拉伸性能及断口特征、晶间腐蚀与剥落腐蚀性能等方法,研究了挤压、轧制、ECAP(等通道转角挤压)、热压缩等变形加工及后续热处理对铝合金组织性能的影响,主要研究结果如下(下文中X方向为挤压态合金轴向,Y方向与ECAP剪切面平行,Z方向为Y方向沿轴向旋转90°):探索出了一套采用常规熔铸(非快速凝固)-挤压-轧制工艺,结合后续热处理(预回复、固溶、T7X-2时效),制备抗拉强度达716MPa,且具有良好抗腐蚀(晶间、剥落)性能超高强铝合金的方法。本文所研究合金经轧制-预回复-固溶-T7X-2(121℃×5 h+133℃×16 h)时效处理后,Z方向硬度达到232.8HV,晶间、剥落腐蚀等级为三级(62.33μm)和EC级;X方向抗拉强度达到716.39MPa,断裂延伸率为8.76%。预回复退火处理促进了第二相的回溶,保留了较多位错,提升了轧制态合金的抗拉强度,提高了合金的电导率与抗腐蚀性能。由合金的拉伸性能测试和XRD组织分析结果显示,轧制材在X、Y方向的微结构与力学性能存在明显的各向异性。本文所研究轧制态合金在T6(121℃×24 h)与T7X-2时效下,抗(晶间、剥落)腐蚀性能相差不大,T7X-1(121℃×5 h+153℃×16 h)时效下,合金的抗腐蚀性能最佳。探索出了一套采用常规熔铸(非快速凝固)-挤压-过时效-ECAP-热压缩工艺,结合后续热处理(固溶、T6时效),制备抗拉强度达696MPa,且具有较好抗腐蚀(晶间、剥落)性能超高强铝合金的方法。本文所研究合金经ECAP-Y向热压-固溶-T6(121℃×24 h)时效处理后,X、Y、Z方向硬度均超过220HV,晶间腐蚀深度均小于131μm、剥落腐蚀等级均达到EC级;X方向抗拉强度达到696.76MPa,断裂延伸率为7.67%。本文所研究的合金在两种热压工艺下的强度、硬度、电导率、抗晶间性能都呈现明显差异。在微结构方面由EBSD与XRD数据分析可以得出,Y向热压下合金发生了动态连续再结晶使晶粒平均尺寸得到细化,晶界平均角度略微变大,低角度晶界百分比降低。这都是由于Y向热压的剪切方向与ECAP挤压的剪切方向夹角更接近于90°,其塑性变形更剧烈所产生的现象。探索出了一套采用常规熔铸(非快速凝固)-挤压-过时效-Bc方式两道次ECAP-热压缩工艺,结合后续热处理(预回复、固溶、T7X-1时效),制备抗拉强度达688MPa,且具有优异抗腐蚀(晶间、剥落)性能超高强铝合金的方法。本文所研究合金经Bc方式两道次ECAP-Z向热压-预回复-固溶-T7X-1时效处理后,X、Y、Z方向硬度均超过214HV,晶间腐蚀深度均小于126μm、剥落腐蚀等级均达到EA级;X方向抗拉强度达到688.20MPa,断裂延伸率6.67%。本文所研究合金经Bc方式两道次ECAP加工后,两种压缩方向(Z、Y)下合金的微结构(平均晶粒尺寸、平均晶界角度、小角度晶界比例)方面呈现较小差异,并且两种热压工艺对合金的硬度、电导率、抗腐蚀性能均无明显影响;说明Bc两道次ECAP可以更大程度上改善了材料微结构与抗腐蚀性能的各项异性。本文所研究合金经Bc方式两道次ECAP-热压缩-预回复-固溶处理后,相较T6时效,T7X-1时效下抗腐蚀(晶间、剥落)性能更优。
[Abstract]:7000 Aluminum Alloy with its own low density, high specific strength, good corrosion resistance and other advantages are widely used in aerospace, weapons manufacturing, automobile and ship manufacturing. This paper developed on the independent innovation of ultra high strength Aluminum Alloy (wt.%) Al-12.51Zn-2.85Mg-2.83Cu-0.18Zr-0.0598Sr profile as the test material, through the microstructure, Electron Backscattered Diffraction (EBSD), X-ray diffraction (XRD), microhardness, electrical conductivity, tensile properties and fracture characteristics, method of corrosion and exfoliation corrosion properties of intergranular, rolling, extrusion, ECAP (ECAP), hot compression deformation and subsequent heat treatment effect on Aluminum Alloy performance. The main results are as follows (X direction below for extruded alloy axial, parallel, Y direction and ECAP direction is Y Z shear plane along the direction of axial rotation of 90 DEG): To explore a set of used Conventional casting (non rapid solidification) - extrusion rolling process, combined with subsequent heat treatment (pre recovery, solid solution, aging, T7X-2) preparation of tensile strength of 716MPa, and has good corrosion resistance (intergranular flaking method) properties of ultra high strength Aluminum Alloy. This paper studies alloy by rolling - pre - reply the solution of -T7X-2 (121 DEG C * 5 h+133 * 16 h) after aging treatment, Z hardness of 232.8HV, intergranular and exfoliation corrosion grade is three (62.33 m) and EC; X direction tensile strength reaches 716.39MPa, the elongation rate of 8.76%. pre annealing treatment promoted back to the second phase solution, retain more wrong, enhance the tensile strength of rolled alloy, improve the electrical conductivity of the alloy and corrosion resistance. The tensile test and XRD microstructure analysis showed that the rolling material in X, microstructure and mechanical properties of Y direction is highly anisotropic. In this paper, the research on rolling 鎬佸悎閲戝湪T6(121鈩兠，

本文编号：1690051