激光沉积制造TiAl合金工艺与组织演变研究
发布时间：2019-03-05 12:17
【摘要】：TiAl金属间化合物合金具有高的比强度、比弹性模量以及优异的高温力学性能,是一种具有巨大发展潜力的航天航空用新型高温结构材料。但TiAl室温塑性差、脆性大、室温延伸率不足3%、机加难度大等固有属性使其成形工艺异常复杂与困难,是TiAl尚未获得大量应用的主要障碍。为克服TiAl合金成形工艺的不足,本文以现阶段应用最为广泛的Ti4822合金(Ti-48Al-2Cr-2Nb,at%)为基础,开展了TiAl合金的激光沉积制造(LDM)工艺研究,分析不同激光沉积制造工艺参数条件下TiAl合金的显微组织与力学性能,以及后续热处理工艺参数对成形后TiAl合金显微组织与力学性能的影响。研究发现,经LDM工艺制备的TiAl合金显微组织特征为等轴状初生晶粒内包含有大量层片状的γ、α2和微量层片状B2相;扫描速度恒定,随着激光功率的增加,初生等轴晶晶粒尺寸逐渐增大,晶内的α2和B2相含量逐渐增加,γ相含量降低,合金显微硬度逐渐增大;激光功率恒定,随着扫描速度的增加,初生等轴晶晶粒尺寸逐渐减小,晶内的α2和B2相含量逐渐减少,γ相含量增加,合金显微硬度逐渐增大。经综合分析认为激光功率1200W、扫描速度7mm/s为优佳的TiAl合金LDM工艺参数。热处理后的TiAl合金显微组织以γ和α2相为主,同时包含微量B2相。1260℃固溶处理后获得双态组织,由块状γ以及层片状间隔分布的γ+α2混合组织构成,XRD谱线中,γ相衍射峰强度和比例略高于α2相,二者体积分数基本相当;1330℃固溶处理后,合金形成近片层组织,主要由层片状γ+α2构成,XRD谱线中γ衍射峰强度和比例较高,体积分数明显高于α2;1350℃固溶处理后同样获得近片层组织,由层片状γ+α2构成,组织内γ相衍射峰强度和比例高于α2相,其α2相比例高于1330℃热处理的TiAl合金。随着热处理温度的升高TiAl合金显微硬度逐渐减小。经热等静压再经同上热处理后,TiAl合金组织中以γ和α2为主,B2相微量,显微组织类型基本相同。在XRD谱线中,随固溶温度升高,γ相衍射峰强度和比例增加,α2衍射峰强度和比例减小,表明γ相含量随固溶温度增加逐渐增大,α2含量随固溶温度增加而减小,B2相含量微量。经(热等静压+热处理)与热处理相比,合金组织结构没有明显改变,组织内的层片尺寸明显有增大。热等静压后随着热处理温度的升高TiAl合金显微硬度逐渐减小,硬度值略大于同等热处理温度而未经热等静压的样品。
[Abstract]:Because of its high specific strength, specific elastic modulus and excellent mechanical properties at high temperature, TiAl intermetallic alloy is a new type of high-temperature structural material for aerospace and aeronautics with great potential for development. However, the inherent properties of TiAl, such as poor plasticity at room temperature, high brittleness, less than 3% elongation at room temperature, and so on, make its forming process extremely complex and difficult, which is the main obstacle to the large-scale application of TiAl. In order to overcome the deficiency of forming process of TiAl alloy, the laser deposition process of Ti4822 alloy (Ti-48Al-2Cr-2Nb,at%) was studied on the basis of Ti4822 alloy (Ti-48Al-2Cr-2Nb,at%), which is the most widely used alloy at present, and the laser deposition technology of (LDM) alloy was studied in this paper. The microstructure and mechanical properties of TiAl alloy under different laser deposition process parameters and the influence of heat treatment parameters on the microstructure and mechanical properties of formed TiAl alloy were analyzed. It is found that the microstructure of TiAl alloy prepared by LDM process is characterized by a large number of lamellar 纬, 伪 2 and micro lamellar B2 phases in equiaxed primary grains. The scanning velocity is constant. With the increase of laser power, the grain size of primary equiaxed crystal increases gradually, the contents of 伪 _ 2 and B _ 2 phases increase gradually, and the content of 纬 phase decreases, and the microhardness of the alloy increases gradually. The laser power is constant, with the increase of scanning speed, the grain size of primary equiaxed crystal decreases gradually, the content of 伪 _ 2 and B _ 2 phase decreases, the content of 纬 phase increases, and the microhardness of the alloy increases gradually. Comprehensive analysis shows that laser power 1200 W and scanning speed 7mm/s are the best technological parameters of TiAl alloy LDM. After heat treatment, the microstructure of TiAl alloy consists mainly of 纬 and 伪 2 phases, and contains a small amount of B 2 phase. After solution treatment at 1260 鈩，
本文编号：2434898
[Abstract]:Because of its high specific strength, specific elastic modulus and excellent mechanical properties at high temperature, TiAl intermetallic alloy is a new type of high-temperature structural material for aerospace and aeronautics with great potential for development. However, the inherent properties of TiAl, such as poor plasticity at room temperature, high brittleness, less than 3% elongation at room temperature, and so on, make its forming process extremely complex and difficult, which is the main obstacle to the large-scale application of TiAl. In order to overcome the deficiency of forming process of TiAl alloy, the laser deposition process of Ti4822 alloy (Ti-48Al-2Cr-2Nb,at%) was studied on the basis of Ti4822 alloy (Ti-48Al-2Cr-2Nb,at%), which is the most widely used alloy at present, and the laser deposition technology of (LDM) alloy was studied in this paper. The microstructure and mechanical properties of TiAl alloy under different laser deposition process parameters and the influence of heat treatment parameters on the microstructure and mechanical properties of formed TiAl alloy were analyzed. It is found that the microstructure of TiAl alloy prepared by LDM process is characterized by a large number of lamellar 纬, 伪 2 and micro lamellar B2 phases in equiaxed primary grains. The scanning velocity is constant. With the increase of laser power, the grain size of primary equiaxed crystal increases gradually, the contents of 伪 _ 2 and B _ 2 phases increase gradually, and the content of 纬 phase decreases, and the microhardness of the alloy increases gradually. The laser power is constant, with the increase of scanning speed, the grain size of primary equiaxed crystal decreases gradually, the content of 伪 _ 2 and B _ 2 phase decreases, the content of 纬 phase increases, and the microhardness of the alloy increases gradually. Comprehensive analysis shows that laser power 1200 W and scanning speed 7mm/s are the best technological parameters of TiAl alloy LDM. After heat treatment, the microstructure of TiAl alloy consists mainly of 纬 and 伪 2 phases, and contains a small amount of B 2 phase. After solution treatment at 1260 鈩，
本文编号：2434898
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