高强度TiZrAl合金的制备及组织性能研究

发布时间：2018-06-10 16:33

本文选题：钛锆基合金 + 成分优化　；参考：《燕山大学》2015年博士论文

【摘要】：钛(Ti)及钛合金由于具有高比强度、优异的耐腐蚀性能和低密度等优点,被广泛的应用于航空航天和化学工业等行业;而与钛同属第IVB的金属元素锆(Zr)及其合金则具有中子吸收截面积小、抗氧化、耐腐蚀、热膨胀系数小等优异的物理化学性能,主要应用于核工业和醋酸工业中。随着科学技术的进步,Ti及Zr合金逐渐在航空航天领域得到应用。然而航空航天事业的不断进步以及空间极其恶劣的服役条件对空间结构材料的性能提出了更苛刻的要求。基于空间飞行器服役的苛刻环境以及Ti和Zr合金的优异物理和力学性能,本文以发展新型空间结构材料为目标,运用多种实验室手段和工业化制备技术,研究了不同成分TiZrAl合金在多种变形工艺和热处理工艺条件下的相组成、微观组织以及力学性能。利用非自耗电弧炉熔炼制备了一系列的TiZrAl合金,研究各组元含量的变化对合金结构与性能的影响。结果表明,Al元素和Zr元素在Ti ZrAl合金中分别起到稳定HCP-α相和稳定BCC-β相的作用,当Zr含量达到40at.%时,β相被完全保留至室温。此外,Al元素和Zr元素能够显著提升TiZrAl合金的力学性能。在TiZrx Aly(x=0-40,y=0-15)合金中,TiZr25Al15合金具有最优异的综合力学性,其抗拉强度能够保持在1300MPa以上,并且具有4.5%-11%的拉伸延伸率。使用10kg悬浮熔炼炉以及100kg自耗电弧炉熔炼制备了TiZr25Al15和TiZr40Al15两种高强度合金。通过调整变形及热处理参数进一步改善和优化合金的综合力学性能。实验结果表明,经过α单相区热轧的TiZr25Al15合金其力学性能明显优于α+β两相区及β单区热轧的TiZr25Al15合金。经过800°C热轧后的TiZr25Al15合金呈现细小的等轴组织,其抗拉强度达到1564Mpa,同时具有9%的延伸率,相比较于铸态合金的拉伸性能(强度1144Mpa,延伸率2.2%),合金强度和延伸率分别提高了36.7%和309%。此外,TiZr25Al15合金经过700°C轧制不同温度退火后,微观组织呈现出明显差异,800°C退火后合金发生完全再结晶并且出现退火孪晶。经过700°C轧制800°C1h退火后的TiZr25Al15合金具有1730MPa的抗拉强度和4.5%的延伸率。在进一步对TiZr25Al15合金退火过程中组织演变的研究中发现,TiZr25Al15合金在α+β两相区或者β单相区保温并经过不同冷却速率冷却后,其次生α相板条宽度与保温温度及冷却速率的关系满足方程b(T0,ν)=0.189[(T0-769)/ν]1/2。研究了TiZrAl合金的相变规律,结果表明Zr在TiZrAl合金中能够增加局部应力起到抑制马氏体形成的作用,并且Zr的添加能够提高TiZr Al合金中β相的结合能起到稳定β相的作用。在TiZrAl合金中,高温淬火得到的α''马氏体相和β相在时效过程中并不能稳定存在,其分解过程分别为α′′→α′′+α→α→α+Ti3Al和β→α+β→α+Ti2AlZr。对TiZrAl合金塑性变形的研究表明,退火态TiZr25Alx(x=0、5、10、15)合金的室温塑性变形机制主要为沿基面{0002}的滑移和少量的棱锥面{10-11}的滑移,并没有观察到孪生变形机制。此外,淬火态TiZr40Al15合金在拉伸过程中将发生应力诱发β相→α''马氏体相转变,其中α''马氏体相与淬火β相之间的位相关系为[111]β//[100]α″。在晶粒尺寸为30-700μm,应变速率为1×10-4/s-1×10-1/s的范围内,随着晶粒尺寸的减小或者应变速率的提高,合金发生马氏体相变的触发应力增加;当应变速率超过1/s时,合金中应力诱发马氏体相变过程被完全抑制,合金的主要变形机制为滑移。
[Abstract]:Titanium (Ti) and titanium alloys have been widely used in aerospace and chemical industries because of their high specific strength, excellent corrosion resistance and low density. The metal element zirconium (Zr) and its alloys, which belong to the same genus IVB with titanium, have excellent physical chemistry, such as small neutron absorption cross section, anti oxidation, corrosion resistance, and low thermal expansion coefficient. Performance, mainly used in the nuclear industry and the acetic acid industry. With the progress of science and technology, Ti and Zr alloys are gradually applied in the aerospace field. However, the continuous progress of the aerospace industry and the extremely bad service conditions of space have put forward more stringent requirements for the performance of space structure materials. For the harsh environment and the excellent physical and mechanical properties of Ti and Zr alloys, the phase composition, microstructure and mechanical properties of different components of TiZrAl alloys under a variety of deformation processes and heat treatment conditions are studied in this paper for the development of new space structure materials. A series of TiZrAl alloys were prepared by the consumable arc furnace. The effect of the change of each component content on the structure and properties of the alloy was studied. The results showed that the Al and Zr elements played a role in stabilizing HCP- a phase and stabilizing the BCC- beta phase in the Ti ZrAl alloy. When the Zr content reached 40at.%, the beta phase was completely retained to room temperature. Furthermore, Al elements were found. The mechanical properties of TiZrAl alloy can be significantly improved by Zr elements. In TiZrx Aly (x=0-40, y=0-15) alloys, the TiZr25Al15 alloy has the most excellent comprehensive mechanical properties. The tensile strength of the alloy can be kept above 1300MPa and has the tensile elongation of 4.5%-11%. 10kg suspension smelting furnace and 100kg self consumable arc furnace are used to prepare TiZr25. Two kinds of high strength alloys, Al15 and TiZr40Al15, are further improved and optimized by adjusting the deformation and heat treatment parameters. The experimental results show that the mechanical properties of TiZr25Al15 alloy after a single phase zone hot rolling are obviously better than that of the TiZr25Al15 alloy of the alpha + beta two phase and the beta single zone hot rolled. After 800 degree C hot rolled TiZr25Al1 The 5 alloy presents a fine equiaxed structure with a tensile strength of 1564Mpa and 9% elongation at the same time. Compared with the tensile properties of the cast alloy (strength 1144Mpa, elongation 2.2%), the strength and elongation of the alloy are increased by 36.7% and 309%. respectively. The microstructure of TiZr25Al15 alloy after annealing at different temperatures in 700 degree C is evident. The alloy has complete recrystallization and annealing twins after 800 C annealing. The TiZr25Al15 alloy after 700 C rolling 800 degrees C1h has 1730MPa tensile strength and 4.5% elongation. In the further study of the microstructure evolution of TiZr25Al15 alloy during annealing, the TiZr25Al15 alloy is in the alpha + beta two phase or beta The relationship between the width of the phase plate and the heat preservation temperature and the cooling rate of the second phase area satisfies the equation B (T0, V) =0.189[(T0-769) / V]1/2.. The results show that the Zr in TiZrAl alloy can increase the effect of local stress on the formation of martensite and Zr in TiZrAl alloy, and Zr. The addition can improve the binding energy of the beta phase in the TiZr Al alloy to stabilize the beta phase. In the TiZrAl alloy, the alpha 'martensitic phase and the beta phase obtained at high temperature are not stable during the aging process. The decomposition processes are alpha', alpha ', alpha to alpha, and beta to alpha to alpha +Ti2AlZr., respectively, on the plastic deformation of TiZrAl alloy. It is shown that the plastic deformation mechanism of the annealed TiZr25Alx (x=0,5,10,15) alloy is mainly the sliding of {0002} along the base surface and the slip of a small number of pyramid surface {10-11}, and the mechanism of twin deformation is not observed. In addition, the stress induced phase transformation of the stress induced beta phase to alpha 'martensitic phase will occur in the tensile process of the quenched TiZr40Al15 alloy, in which the stress induces the phase transformation of the beta phase to alpha' martensitic phase. The phase relation between the alpha 'martensitic phase and the quenched beta phase is [111] beta //[100] alpha. In the range of 30-700 mu m and the strain rate of 1 x 10-4/s-1 x 10-1/s, with the decrease of grain size or the increase of the strain rate, the triggering stress of martensitic transformation occurs in the alloy; when the strain rate exceeds 1/s, the stress induced in the alloy is induced. The martensitic transformation process is completely inhibited, and the main deformation mechanism of the alloy is slip.
【学位授予单位】：燕山大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG146.23

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