化学热处理表面改性对TiAl基合金抗高温氧化性能的影响EI

研究了渗碳处理对Ｔｉ－４８Ａｌ－２Ｃｒ－２Ｎｂ（ａｔ．％）合金高温循环氧化性的影响。试验发现，表面渗碳处理能够显著地改善ＴｉＡｌ基合金抗高温氧化能力。使用ＳＥＭ、波谱分析、能谱分析和Ｘ射线衍射分析，研究了渗碳处理提高ＴｉＡｌ基合金抗高温氧化性能的机理。     

TiAl合金离子渗碳摩擦磨损性能研究

对TiAl合金进行离子渗碳处理以提高其耐磨性.利用摩擦磨损试验机对TiAl渗碳后的室温及600℃高温干摩擦磨损性能进行了研究,采用扫描电镜、能谱、辉光放电光谱仪、X射线衍射仪等手段观察分析了磨痕的形貌和成分以及渗碳层组织与相结构.研究表明,TiAl合金经离子渗碳处理后形成一定厚度的含硬质Ti2A1C的渗碳层,其室温摩擦...     

On the mechanism of crack propagation resistance of fully lamellar TiAl alloy

The study was done using notched two-colony thick tensile specimens of a directionally solidified cast fully lamellar TiAl alloy. In-situ observations of fracture processes in scanning electron microscope (SEM) were combined with section-to-section related observations of fracture surfaces to investigate the crack growth process. Finite element method (FEM) calculations are carried out to evaluate the stresses for propagating cracks. The results reveal that: (1) the reason why enhancement of applied load is required to propagate the main crack, was attributed to that the main crack observed at the surface did not extend all the way through the specimen's thickness thus the stress field was still controlled by the notch, in which a definite stress required for extending a crack tip should be kept by increasing the applied load. (2) Crack propagation resistance is enhanced at colony boundaries, only when a change occurs from an inter-lamellar propagation to a trans-lamellar propagation (3) Ligament bridging toughening phenomena can be integrated into aforementioned mechanism. As a whole the processes of new crack nucleation with bridging ligament formation decreases the crack propagation resistance rather than increasing it. (4) In case the majority of microcracks are surface cracks, the effect of microcrack shielding is not obvious.     

TiAl基金属间化合物研究进展

与普通超合金相比，TiAl基金属间化合物以其优异的性能在航空和汽车工业中应用越来越广泛，本文总结了TiAl基合金在微观结构控制、微观组织对性能影响、合金化、熔炼技术、加工技术以及应用等方面的研究进展。     

Electron Structure of γ/α2 Phase Boundaries in TiAl Based Alloys

The valence electron structure of γ/α2 phase boundaries in lamellar colonies in Ti-47Al-2M (M=Nb, Cr, V) (at. Pct) was investigated by empirical electron theory of solid and molecules (EET) and its bond-length-difference (BLD) method     

γ-TiAl基合金快速熔凝组织转变的规律

采用激光表面快速熔凝技术处理了γ-TiAl基合金的拟连接表面，原位观察了激光处理组织在不同温度下保温过程中组织转变的特点，研究了处理温度对组织转变速度的影响以及组织细化的规律，结果表明，用激光表面快速熔凝处理所得到的γ-TiAl基合金拟连接表面的枝晶组织，在一定的温度下可转变为细小的等轴晶粒组织，为后续的超塑连接提供了良好的保障。     

钛铝基合金离子碳氮共渗及其耐磨性的研究

为提高TiAl基合金的耐磨性及抗高温氧化性,利用渗氮在TiAl基合金表面形成氮化物,以提高耐磨性;渗碳形成致密且与基体结合牢固的碳化物层,提高抗高温、抗氧化性;将二者结合,采用辉光离子碳氮共渗的方法,研究了渗层的相结构组成、不同工艺参数对TiAl基合金离子碳氮共渗后渗层厚度以及表面硬度和耐磨性的影响.结果表明:TiAl基合金共渗层是由碳氮化合物层与过渡层组成的复合相结构;随共渗温度的升高和时间的延长,渗层厚度增加;与未经共渗处理的试样相比,表面硬度及耐磨性显著提高.X射线衍射结果显示,渗层主要由TiC,TiN,AlTi3,Al2O3等组成.     

TiAl合金表面激光重熔热障涂层组织及抗高温氧化性能

为了进一步提高TiAl合金表面等离子喷涂ZrO2-7%(质量分数)Y203热障陶瓷涂层的性能,采用激光重熔工艺对涂层进行处理,研究了激光重熔对涂层微观组织和抗高温氧化性能的影响.用扫描电镜(SEM)分析了涂层形貌和微观结构,同时对其抗高温(850℃)氧化性能进行了考察.结果表明,等离子喷涂热障陶瓷涂层呈典型的层状堆积特征,有一定的孔隙且分布有微裂纹;经过激光重熔处理后,陶瓷涂层片层状组织得以消失,致密性提高,获得了基本没有裂纹等缺陷的重熔层;整个重熔层包括界面没有明显特征的平面晶和上部沿热流方向生长的柱状晶组织.等离子喷涂热障涂层具有较好的抗高温氧化性能,经过激光重熔后可进一步提高其抗高温氧化能力.     

TiAl基合金环境脆性的研究

研究了不同环境气氛对成分为Ｔｉ－４６Ａｌ－２Ｃｒ－０．２Ｓｉ－０．１Ｎｄ（ａｔ％）的ＴｉＡｌ基合金室温塑性的影响。结果表明该合金在室温下对环境脆性是敏感的，在不同气氛中的拉伸塑性依次为Ｏ２〉Ａｉｒ（空气）〉Ｈ２〉Ａｒ＋Ｈ２Ｏ。水汽和氢气均引起环境脆性，但水汽比氢气更有害。     

Microstructure and strength of diffusion-bonded joints of TiAl base alloy to steel

Diffusion bonding of TiAl-based alloy to steel was carried out at 850–1100 °C for 1–60 min under a pressure of 5–40 MPa in this paper. The relationship of the bond parameters and tensile strength of the joints was discussed, and the optimum bond parameters were obtained. When products are diffusion-bonded, the optimum bond parameters are as follows: bonding temperature is 930–960 °C, bonding pressure is 20–25 MPa, bonding time is 5–6 min. The maximum tensile strength of the joint is 170–185 MPa. The reaction products and the interface structures of the joints were investigated by scanning electron microscopy (SEM), electron probe X-ray microanalysis (EPMA) and X-ray diffraction (XRD). Three kinds of reaction products were observed to have formed during the diffusion bonding of TiAl-based alloy to steel, namely Ti₃Al+FeAl+FeAl₂ intermetallic compounds formed close to the TiAl-based alloy. A decarbonised layer formed close to the steel and a face-centered cubic TiC formed in the middle. The interface structure of diffusion-bonded TiAl/steel joints is TiAl/Ti₃Al+FeAl+FeAl₂/TiC/decarbonised layer/steel, and this structure will not change with bond time once it forms. The formation of the intermetallic compounds results in the embrittlement of the joint and poor joint properties. The thickness of each reaction layer increases with bonding time according to a parabolic law. The activation energy Q and the growth velocity K₀ of the reacting layer Ti₃Al+FeAl+FeAl₂+TiC in the diffusion-bonded joints of TiAl base alloy to steel are 203 kJ/mol and 6.07 mm²/s, respectively. Careful control of the growth of the reacting layer Ti₃Al+FeAl+FeAl₂+TiC can influence the final joint strength.     

TiAl基合金表面改性对高温抗氧化性的影响

研究了渗碳处理ＴｉＡｌ基合金试样的高温氧化行为，发现渗碳处理可以在ＴｉＡｌ基合金试样表层形成致密的多层结构的渗碳层，并发生表层Ａｌ、Ｔｉ重新分配。致密的渗碳层具有良好的高温抗氧化性和高温热稳定性，同时，Ｔｉ、Ａｌ重新分配形成的富Ａｌ最外层也能进一步提高合金的抗氧化性。