7055高强铝合金热加工工艺基础研究

【作者】 黄继武；

【导师】 尹志民；

【作者基本信息】 中南大学 ， 材料物理与化学， 2004， 硕士

【摘要】 7055高强铝合金是航天航空用轻质结构材料，铸锭均匀化工艺和热加工工艺是这种合金制备的关键技术，热轧板材的各向性能也是人们关注的焦点。本工作采用室温拉伸试验、硬度测试、电导率测定、金相分析、SEM、TEM和XRD等分析方法研究了7055高强铝合金的铸态、不同均匀化处理态和热轧制态组织和性能的变化规律；采用热模拟技术研究了不同热加工参数条件下合金应力—应变关系，旨在为热加工制度的制订提供参考。研究结果表明： 1．7055合金铸锭表现为明显的枝晶偏析，均匀化过程中，显微组织结构发生两方面的变化：一方面，半连续激冷铸造的过饱和固溶体枝晶组织和枝晶间粗大的平衡相随均匀化温度的升高和时间的延长而消失；另一方面，400℃以下均匀化，过饱和固溶体中分解析出平衡的η（MgZn₂）相和S（Al₂CuMg）相，400℃以上均匀化，析出的平衡相又回溶到固溶体基体中。合宜的均匀化处理工艺为450℃下保温24h。 2．7055合金高温压缩变形时的流变应力取决于变形温度和变形速率，流变应力随变形温度的升高而减小，随变形速率的提高而增大。热变形条件下流变应力σ、应变速率（?）和变形温度T之间满足下列关系式：（?）=e^-4.3342[sinh（0.01567σ）]^4.749471exp（-196263/RT） 3．7055合金在450℃以下热变形，热变形组织主要为动态回复，在450℃以上热变形，热变形组织有动态再结晶发生。7055合金较合宜的热加工温度为400℃左右。 4．7055合金热轧板材中的主要织构为{110}＜112＞织构。7055合金热轧板材的性能表现出各向异性。轧制方向的强度最高，延伸率较低，随着与轧向取向角的增大，强度逐渐降低，横向（取向角为90°）强度比轧向强度降低了16％。延伸率则不同，随着与轧制方向取向角的增大，延伸率先升后降，取向角为60°时的延伸率最高，比轧向和横向延伸率高出约1倍。更多还原

【Abstract】 High strength 7055 aluminum alloy is a structure material of light weight used in the area of aviation and spaceflight. The homogenization process and hot machining process of the ingot is the key technology of this alloy, the property of the hot rolling plate is also the center of people’ attention. In this work, the laws of microstructure and property evolution of 7055 alloy on the as-cast, different homogenization treatment and hot rolling conditions have been studied using the analysis method of room temperature tensile test, hardness and conductivity test, OM observation, SEM, TEM and XRD. The relation between stress and strain of the alloy on the different hot machining parameter conditions has been investigated by thermol-simulation technology, the purpose is to provide conferences for stipulating for the hot machining process. The conclusions can be summarized as follows:1.The ingot of 7055 alloy shows apparently dendrite segregation phenomena. During the course of homogenization, the variety of microstructure shows in two sides: on the one side, the dendrite structure and coarse equilibrium phases between dendrites of super saturation solution disappear gradually as the homogenization temperature increase and the homogenization time prolong; on the other hand, when the alloy was homogenized under the temperature of 400 ℃, the super saturation solution decompounded and separated out equilibrium n (MgZn2) and S(Al2CuMg) phases, when the alloy was homogenized on the temperature of high than 400癈, the equilibrium phases re-dissolved into the solution matrix. The suitable homogenization treatment process is 450℃/24h.2. The flow stress of 7055 alloy under high temperature compress deformation is controlled by both deforming temperature and strain rate, the flow stress decreases with the increase of deforming temperature, while increase with the increase of strain rate. Under the deformation condition, the relation of the flow stress, strain rate and the deformation temperature is showed as follows:3. When 7055 alloy is deformed on the temperature of less than 450℃, the hot deformation structure is mainly dynamic recovery structure. When 7055 alloy is deformed on the temperature of more than 450℃, a few recrystalizaion structure can be observed in the hot deformation structure. The favorable hot processing temperature is approximately 400℃.4. The main texture of the hot rolling plate of 7055 alloy is {110}<112>.The properties of the hot rolling plate of 7055 alloy in different direction is different (anisotropy),the strength is the highest and the elongation is relatively low in rolling direction, as the tropism angle with the rolling direction increase, the strength decrease gradually and the strength decrease 16% in the long-transverse direction than in the rolling direction. But the elongation is different, as the tropism angle with the rolling direction increase, the elongation increases firstly and then decreases, when the tropism angle is 60?, the elongation is the highest and is double more than the elongation in rolling and transverse directions.更多还原