7A04铝合金棒材力学性能各向异性研究

发布时间：2018-04-09 18:55

本文选题：7A04铝合金　切入点：变形温度　出处：《中北大学》2011年硕士论文

【摘要】：超高强度铝合金由于具有质量轻、比强度高、韧性较好、热加工性能好以及可热处理等优良的性能，一直在交通运输、航空航天、节能减排等领域发挥着重要的作用。在铝合金棒材的生产和加工过程中，不可避免的会带有一定强度地纤维状晶粒和织构。而它们所引起的各向异性会对铝合金材料的塑性变形产生严重的影响。因此如何控制纤维状晶粒和织构的不良影响，并最大程度的利用它们发挥出铝合金的潜在力学性能，，一直是材料工程领域重要的课题。本文采用室温拉伸实验、高温压缩实验、金相观察、x-射线衍射等分析方法研究了在不同变形温度下7A04铝合金力学性能与微观组织的变化规律，旨在为热加工制度的制定、合金组织与性能的预测和控制等提供参考。对变形温度的研究表明，变形初期(达到真应力峰值前)，流动应力随应变的增加而迅速增加，当应变超过一定值后，流动应力开始稍微下降并逐渐趋于稳定，出现了稳态流动特征；在给定应变速率的条件下，流动应力随着温度的升高而显著降低，且合金流动应力进入稳态流动时所需的应变也随着温度的升高而减小。对材料的金相观察表明：随着压缩变形温度的升高，晶粒会有明显长大的现象。对应变速率的研究表明，7A04铝合金在320℃压缩载荷作用下，在与合金棒材挤压方向成O。、90。两个方向下，应变率敏感性部比较低；而在400℃、480℃时铝合金对应变速率非常敏感。对材料的金相观察表明：在温度不变时，在低应变速率(ε=0．1s~(-1))和高应变速率(ε=1s~(-1))压缩载荷作用下变形时，晶粒的大小没有明显的变化。对各向异性的研究表明，在常温拉伸状态(ε=1.3×10~(-3)s~(-1))下和在低应变速率(ε=0．1s~(-1))、温度较低(T=320。C)的热模拟压缩状态下时，7A04铝合金在O。、45。、90。三个方向上的力学性能差异较大。随着温度的升高，材料的力学性能趋于各向同性。织构检测发现:材料中有典型“铜型”和“黄铜型”特征织构,强度分别为6级和8级。还有少量的立方织构和戈斯织构,强度都为3级。在纤维状晶粒和织构的耦合作用下,使合金产生了各向异性。
[Abstract]:Ultra high strength Aluminum Alloy due to the advantages of light weight, high strength, good toughness, good thermal processing performance and heat treatment and other excellent properties, has been in the transportation, aerospace, energy conservation and other areas play an important role in the production and processing Aluminum Alloy bar, inevitably with certain the strength of fibrous grain and texture. And their anisotropy caused by plastic deformation will have a serious impact on Aluminum Alloy materials. So how to control the adverse effects of fibrous grain and texture, and they use the maximum potential mechanical properties of Aluminum Alloy, has been an important task in material engineering field.
The room temperature tensile test, high-temperature compression test, metallographic observation, x- ray diffraction analysis method to study the variation at different deformation temperatures and mechanical properties and microstructure of 7A04 Aluminum Alloy, aims to develop for the thermal processing system, provide reference for the alloy microstructure and properties prediction and control.
Study shows that the deformation temperature, initial deformation (really reach the peak stress before), the flow stress increases rapidly with the increase of strain, when the strain exceeds a certain value, the flow stress was slightly decreased gradually stabilized, the steady flow characteristics; at a given strain rate under the condition of flow stress with the increase of temperature and significantly decreased, and the alloy flow stress and strain are required to enter steady state flow also decreases with the increase of temperature. The material metallographic observation showed that: with the deformation temperature, the grain will be significantly long big phenomenon.
Study on the strain rate showed that 7A04 Aluminum Alloy compression load at 320 DEG C, in O. alloy extrusion direction, 90. in two directions, strain rate sensitivity of relatively low; and in 400 C, 480 C Aluminum Alloy is sensitive to the strain rate. The material that observe the metallographic observation: at the same temperature, at low strain rate (=0.1s~ (-1)) and high strain rate (=1s~ (-1)) deformation under compression, the grain size did not change significantly.
Study on anisotropy show that in tensile state (=1.3 * 10~ (-3) s~ (-1)) and at low strain rate (=0.1s~ (-1)) and low temperature (T=320.C) of the thermal simulation compression state, 7A04 Aluminum Alloy in O., 45., mechanical 90. the three directions can differ greatly. With the increase of temperature, the mechanical properties of the material tends to be isotropic.
Texture detected: typical "copper" and "brass" characteristics of textured materials, strength were 6 and 8. There is a small amount of cube texture and texture of Goss, the strength of 3. In the coupling of fibrous grain and texture, so that the alloy has anisotropy.

【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TG146.21

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