摘要
随着科学技术和国防工业的发展,人们对高强度铝合金的要求越来越高,目前,工业生产都在尽可能地提高高强度铝合金的加热温度,同时,高强度铝合金的变形温度范围比较狭窄,因此,在高强度铝合金高温变形研究方面,必须开展大量的工作。本文采用硬度、室温拉伸、金相、SEM等分析方法研究了7A04铝合金在不同变形温度和变形次数下组织与性能的变化规律,为热加工制度的制定提供参考与依据。
研究表明,随着变形温度的升高, T5态和T6态铝合金强度、硬度、塑性均呈先升高后降低的趋势,480℃时为最高点,温度继续升高,性能下降。随着变形次数增加,T5态合金强度、硬度上升,塑性下降;T6态合金则当变形次数小于四次时,强度、硬度和塑性均上升,五次成形时降低。
7A04铝合金高温变形主要以动态再结晶为主。变形温度的升高,能促进动态再结晶地进行;适当增加变形次数,也能促进动态再结晶地顺利进行。
变形温度和变形次数对合金的断裂方式都有所影响,7A04铝合金的断裂方式主要为韧窝断裂和沿晶断裂,过烧后,晶界间结合力被弱化,出现沿晶脆性断口;T6态较T5态韧窝大,数量少,韧性差。7A04铝合金过烧后,综合性能急剧下降,材料报废,工业生产应尽量避免。
通过本实验,可以确定7A04铝合金的最佳成形工艺为480℃四次成形,然后进行T6(470℃×45min固溶+130℃×16h时效)热处理后,其力学性能可达到:σb=590.8Mpa,σ0.2=531.9Mpa,δ=12.5%,ψ=18.4%。
As science and technology and defense industries, people are increasingly demanding high strength aluminum alloy high, at present, industrial production increased in high strength aluminum alloy as much as possible the heating temperature, while the deformation temperature, high strength aluminum alloy Relatively narrow range, therefore, high strength aluminum alloy high temperature deformation, the need for a lot of work.In this paper, hardness, room temperature tensile, metallographic, SEM, analysis of the 7A04 aluminum alloy at different deformation temperature and deformation microstructure and properties of the number of changes under the law for the thermal processing system has been developed to provide reference and basis.
The results show that, with the deformation temperature, T5 and T6 state alloy state strength, hardness, plasticity showed increased first and then decreased, 480℃when the highest point, the temperature continues to rise, performance degradation. with Deformation increase in the number, T5 alloy strength, hardness increase, plastic drop; T6 alloy is less than four times the number when the deformation, strength, hardness and ductility are increased, forming five times lower.
7A04 aluminum alloy high temperature deformation based mainly on dynamic recrystallization. Deformation temperature, can promote the dynamic recrystallization manner; appropriate increase in the number of deformation, but also can promote the dynamic recrystallization to proceed smoothly.
The number of deformation temperature and deformation mode of the fracture has implications, 7A04 aluminum alloy fracture mode mainly intergranular fracture and dimple fracture, had burned, the binding force between the grain boundary is weakened, brittle fracture occurs along the grain; T6 state than the T5 state dimple large number of small, poor toughness. 7A04 aluminum alloy had burned, the sharp decline in overall performance, material scrap, industrial production should be avoided.
Through this experiment, the best 7A04 aluminum alloy forming process for forming four 480℃, and then T6 (470℃×45min +130℃×16h aging solution) heat treatment, the mechanical properties can be achieved:σb = 590.8 Mpa,σ0.2 = 531.9Mpa,δ= 12.5%,ψ= 18.4%.
引文
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