Abstract By means of creep properties measurement and microstructure observation, the deformation and damage behavior of an as-cast TiAl-Nb alloy during creep at temperature near 750 °C were investigated. The results showed that the microstructure of the alloy consisted of lamellar γ/α2 phase, and the boundaries consisted of γ phase located in between lamellar γ/α2 phases with different orientations. In the latter stage of creep, the dislocation networks appeared in the interfaces of lamellar γ/α2 phases due to the coarsening of them, which made the coherent interface transforming into the semi-coherent one for reducing its adhesive strength. The deformation mechanism of the alloy during creep was twinning and dislocations slipping within lamellar γ/α2 phases. In the later period of creep, significant amount of dislocations plied up in the interfaces of lamellar γ/α2 phases, which may cause the stress concentration to promote the initiation and propagation of the cracks along the lamellar γ/α2 interfaces perpendicular to the stress axis. Wherein, some cracks on the various cross-sections were connected by tearing edge along the direction of maximum shear stress, up to the creep fracture, which is considered to be the damage and fracture mechanism of alloy during creep at 750 °C.
Last. Rui Hu(NPU: Northwestern Polytechnical University)H-Index: 21
view all 5 authors...
Abstract An accurate temperature-controlled approach was developed to investigate the microstructure evolution of a high-Nb-containing TiAl alloy. The Ti-45Al-8.5Nb-(W, B, Y) alloy was subjected to controlled heating and cooling from the single β phase region (1500 °C) under various processing parameters. Three typical microstructures involving full lamellar (FL), near lamellar (NL) and quenched martensite plates exist in the cooled microstructures. The initial microstructural homogeneity obtain...
#1Sugui Tian(SUT: Shenyang University of Technology)H-Index: 17
#2Xiaoxia Lv(SUT: Shenyang University of Technology)H-Index: 1
Last. Haofang Sun(SUT: Shenyang University of Technology)H-Index: 3
view all 6 authors...
Abstract By means of creep properties measurement and microstructure observation, an investigation has been made into the creep behaviors and deformation features of TiAl–Nb alloy with various states at high temperature. Results show that the microstructure of as-cast alloys consists mainly of lamellar γ/α 2 phases with various orientations, the boundaries located in between the ones consist of single γ phase. The bigger plastic deformation of alloy during forging may refine the grains and incre...
#1Sugui Tian(SUT: Shenyang University of Technology)H-Index: 17
#2Qi Wang(SUT: Shenyang University of Technology)H-Index: 2
Last. Qiuyang Li(SUT: Shenyang University of Technology)H-Index: 8
view all 5 authors...
Abstract By means of heat treatment, creep properties measurement and microstructure observation, an investigation has been made into the influence of heat treatment on microstructure and creep properties of the high Nb-TiAl alloy. Results show that the microstructure of as-cast high Nb-TiAl alloy consists of lamellar γ/α2 phases with various orientations. The irregular serrated boundaries with single γ phase are located in between the lamellar γ⧸α2 phases with various orientations. After soluti...
#1H.Z. Niu(HIT: Harbin Institute of Technology)H-Index: 9
#2Yu Yong Chen(HIT: Harbin Institute of Technology)H-Index: 20
Last. Li Juan Xu(HIT: Harbin Institute of Technology)H-Index: 6
view all 4 authors...
Abstract A new beta gamma TiAl alloy Ti-43Al-4Nb-2Mo-0.5B (at %) was fabricated by ISM method. The as-cast microstructure consisted of fine lamellar colonies and mixtures of small γ and B2 grains around lamellar colony boundaries. By canned hot forging, the cast microstructure was further refined and homogenized. Microstructure evolution during hot forging was characterized by means of SEM, TEM and EBSD in detail. DRX and phase transformation during forging are also discussed; Based on nano-inde...
Grain refinement in Ti44Al8Nb1B was studied using directional solidification technique and SEM EBSD analysis. Grain refinement occurred during beta-to-alpha transformation through boride assisted alpha nucleation mechanism rather than during solidification. Burgers and non-Burgers alpha2 grain coexisted and they were inoculated by boride precipitates. The orientation relationship between alpha and the B27 TiB precipitates is α2//[010]B27 and (0001)α2//(001)B27. The Burgers alpha variants were in...
#1Chen Guoqing(HIT: Harbin Institute of Technology)H-Index: 3
#2Zhang Bing-gang(HIT: Harbin Institute of Technology)H-Index: 4
Last. Feng Jicai(HIT: Harbin Institute of Technology)H-Index: 9
view all 4 authors...
Abstract Electron beam welding experiments on 2.5-mm-thick as-forged Ti–43Al–9V–0.3Y intermetallic plates were carried out. Cold cracking occurred in the direct electron beam welding joints because of the brittleness of the microstructure and the residual stress. A crack-free electron beam welding joint was obtained by a new composite control method. This process can prolong the high temperature stage to promote the phase transformation and to give the expected microstructure of the joint. The m...
Abstract Ti–47Al–2.5V–1Cr and Ti–40Al–2Cr (at.%) intermetallic alloys was fabricated by the laser melting deposition (LMD) manufacturing process. The microstructure was characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The room-temperature (RT) tensile properties and Vickers hardness of the as-deposited and heat-treated specimens were evaluated on longitudinal directions. Results shows that full densi...
#1Chen Chen(CAS: Chinese Academy of Sciences)H-Index: 4
#1Chao Chen(CAS: Chinese Academy of Sciences)H-Index: 12
Last. Huangqing Ye(CAS: Chinese Academy of Sciences)H-Index: 13
view all 6 authors...
The orientation relationship (OR) and the interface structure between TiB precipitate and gamma-TiAl phase have been investigated using high-resolution electron microscopy. The OR was determined to be [0 (1) over bar0](TiB)parallel to[1 (1) over bar0](gamma), (100)(TiB)parallel to(11 (2) over bar)gamma: This OR has been predicted precisely by the method of coincidence of reciprocal lattice points. The basic vector transformation matrix was also calculated. Based on the investigation of the inter...
#1Y.L. Wang(USTB: University of Science and Technology Beijing)H-Index: 7
#2Junpin Lin(USTB: University of Science and Technology Beijing)H-Index: 23
Last. Guoliang Chen(USTB: University of Science and Technology Beijing)H-Index: 14
view all 5 authors...
Abstract Diffusion behavior of Nb in elemental powder metallurgy high Nb containing TiAl alloys was investigated. The results show that Nb element dissolves into the matrix by diffusion. Pore nests are formed in situ after Nb diffusion. With the increase in hot pressing temperature, the diffusion of Nb will be more sufficient, and the microstructure is more homogeneous. Nb element diffuses completely at 1400°C. Meanwhile, compression deformation and agglomeration phenomena of pores are observed ...
Abstract Three gamma TiAl alloys having compositions within the range of Ti–45Al–6Nb–0.4C–0.2Si–xB–yCr–z(W+Hf) were produced into 6.3 cm diameter ingots by the ingot-skull melting (ISM) technique. Billets from the ingots were hot-worked by the so-called ‘alpha extrusion» process that yields in situ lamellar structures. Isothermal aging experiments at 900 and 1000 °C were conducted on the extruded material to investigate the microstructural stability and consequential strength variations. Microst...