抗Zr“中毒”Al-Ti-B-C中间合金及其对7050合金细化新工艺研究

发布时间：2018-01-31 00:39

本文关键词： 7050铝合金晶粒细化抗Zr 中毒中间合金力学性能　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：7050铝合金因具有高强、高韧、低密度、抗疲劳等特性被广泛应用于汽车、建材、航空航天等领域。7050铝合金为热处理强化变形铝合金,晶粒细化一方面可提高该合金塑性有助于变形,另一方面可进一步增强合金强度。Zr元素在7050铝合金中扮演着不可或缺的角色,比如抑制回复再结晶、时效析出强化等。中间合金细化7050铝合金研究较多,但是均没有很好的解决细化"中毒"问题,大大限制了该合金的应用发展。基于此,本课题制备了一种Al-Ti-B-C中间合金,用于7050铝合金的细化,分析了 Al-Ti-B-C抗Zr"中毒"机理并优化中间合金成分,制备一种细化效果良好的抗Zr "中毒"的中间合金。最后,开发了一种适用于7050铝合金的细化新工艺。本文的主要研究内容如下:(1)Al-5Ti-0.8B-0.2C中间合金对7050铝合金的细化行为Al-5Ti-1B、Al-4Ti-1C、Al-5Ti-0.8B-0.2C 中间合金均可细化 7050 铝合金,但当Zr元素存在时,Al-5Ti-1B、Al-4Ti-1C中间合金中部分粒子与Zr发生反应,引起细化"中毒"从而减弱细化效果;相比之下,Al-5Ti-0.8B-0.2C中间合金含有掺杂型的TiB2、TiC粒子,表现出良好的抗Zr "中毒"能力,当添加0.2%(质量分数/%,下同)时,7050铝合金平均晶粒尺寸由20μm细化至(60±5)μm,细化后合金的室温极限拉伸强度由405MPa提高到515MPa,提高了 27.2%,伸长率由2.1%提高到4.1%。(2)Al-Ti-B-C中间合金成分优化及其对7050铝合金细化的影响基于上述研究,Al-5Ti-0.8B-0.2C中间合金具有一定的抗Zr "中毒"能力,但仍需进一步优化该中间合金成分提高其细化效果和抗衰退性,为此制备了Al-3Ti-0.8B-0.2C、Al-5Ti-0.3C-0.2B、Al-5Ti-0.3B-0.2C 三种中间合金。试验结果表明:保温5min时,四种中间合金对7050铝合金细化效果较好、抗Zr "中毒"能力较强;延长保温时间至60min,Al-5Ti-0.3B-0.2C中间合金细化效果和抗Zr"中毒"能力最优,Al-5Ti-0.3B-0.2C中间合金可应用于7050铝合金的细化试验。(3)Al-5Ti-0.3B-0.2C中间合金添加量对7050铝合金微观组织和力学性能的影响基于上述研究,本部分系统研究了 Al-5Ti-0.3B-0.2C中间合金添加量(0,0.2%,0.5%,1%)对7050铝合金微观组织和力学性能的影响,添加量为0.5%时,合金铸态晶粒尺寸最小并达到晶粒细化极限。未细化和经1%A1-5Ti-0.3B-0.2C中间合金细化的7050铝合金挤压杆(固溶态)发生完全回复再结晶,添加量为0.2%和0.5%时,合金挤压杆部分发生再结晶但基本保留了挤压形成的纤维状织构,Ti元素过高会影响Zr元素抑制回复再结晶的作用。经0.5%Al-5Ti-0.3B-0.2C中间合金细化的7050铝合金挤压杆力学性能最高,极限拉伸强度为697MPa,比未细化的合金提高了 7.2%;伸长率为16.4%,提升了 57.5%。
[Abstract]:Because of its high strength, high toughness, low density and fatigue resistance, 7050 aluminum alloy has been widely used in automobile, building materials, aerospace and other fields. Grain refinement can improve the plasticity of the alloy to help deformation, on the other hand can further enhance the strength of the alloy. Zr plays an indispensable role in 7050 aluminum alloy, such as inhibition of recovery recrystallization. Aging precipitation strengthening and so on. There are many researches on refining 7050 aluminum alloy, but none of them has solved the problem of refining "poisoning", which greatly limits the application development of the alloy. In this paper, a Al-Ti-B-C master alloy was prepared for refining 7050 aluminum alloy. The mechanism of Al-Ti-B-C resistance to Zr poisoning was analyzed and the composition of master alloy was optimized. Preparation of a fine refining effect of Zr "poisoning" master alloy. Finally. A new refining process for 7050 aluminum alloy has been developed. The main contents of this paper are as follows: 1). Refinement behavior of Al-5Ti-0.8B-0.2C master alloy on 7050 aluminum alloy Al-5Ti-1B. Al-4Ti-1CU Al-5Ti-0.8B-0.2C master alloy can refine 7050 aluminum alloy, but when Zr element exists, Al-5Ti-1B alloy can be refined. Some of the particles in Al-4Ti-1C master alloy react with Zr, which results in the refinement "poisoning" and thus weakens the refining effect. In contrast, Al-5Ti-0.8B-0.2C master alloy contains doped TiB2TiC particles, showing good resistance to Zr "poisoning". The average grain size of the alloy was refined from 20 渭 m to 60 卤5 渭 m. The room temperature ultimate tensile strength of the refined alloy was increased from 405 MPA to 515 MPA, which increased by 27.2%. The composition optimization of Al-Ti-B-C master alloy and its effect on the refinement of 7050 aluminum alloy are based on the above research. Al-5Ti-0.8B-0.2C master alloy has the ability to resist Zr poisoning, but it is still necessary to optimize the composition of the master alloy to improve its refining effect and resistance to decay. For this reason, Al-3Ti-0.8B-0.2CU Al-5Ti-0.3C-0.2B was prepared. The experimental results show that the four master alloys have better refining effect on 7050 aluminum alloy after holding for 5 minutes. The ability of anti-Zr poisoning is strong; The refining effect of Al-5Ti-0.3B-0.2C master alloy and the resistance to Zr "poisoning" were optimized by prolonging the holding time to 60 min. Al-5Ti-0.3B-0.2C master alloy can be used in refining test of 7050 aluminum alloy. The effect of Al-5Ti-0.3B-0.2C Master Alloy addition on the Microstructure and Mechanical Properties of 7050 Aluminum Alloy based on the above study. In this part, the effect of Al-5Ti-0.3B-0.2C master alloy on the microstructure and mechanical properties of 7050 aluminum alloy was studied. When the amount added is 0.5. The grain size of the as-cast alloy is minimum and the grain refinement limit is reached. Unrefined and refined 7050 aluminum alloy extruded bar (solid solution) with 1-5Ti-0.3B-0.2C master alloy. Complete recovery recrystallization occurs. When the addition amounts are 0.2% and 0.5 respectively, the recrystallization of the extruded bar takes place, but the fibrous texture formed by the extrusion is basically retained. Excessive Ti element will affect the effect of Zr element on recrystallization. The mechanical properties of 7050 aluminum alloy refined by Al-5Ti-0.3B-0.2C master alloy are the highest. The ultimate tensile strength of the alloy is 697MPa, which is 7.2% higher than that of the alloy without refinement. The elongation was 16.4, up 57.5%.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG292

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