The nickel-based superalloy is among the most important high-temperature structural materials, of which the casting microstructure and especially the dendrite structure can affect the final performance of the superalloy parts. In this work, the phase-field model was coupled with thermodynamic database to simulate the dendrite growth in the multicomponent nickel-based superalloy solidification. And the GPU device was used to accelerate the computation and large-scale phase-field simulations were achieved. The single-crystal dendrite growth was simulated, and the results exhibit a transient and stable growth stages during the formation of primary dendrite arms. The dendrite competitive growth in bicrystal directional solidification (θ=±15°) was also investigated. And the favorable oriented dendrites were able to overgrow the unfavorable oriented dendrites in diverging grain boundary. While the grain boundary remains unchanged in the converging dendrite growth simulation. At last, the effects of natural convection on dendrite growth were investigated, and the simulated microsegregation pattern of the alloy components agreed well with the experimental results.
High temperature titanium alloy has the advantages of high specific strength, high temperature resistance, creep resistance, and good fatigue performance. It is an important structural material for key components such as aero-engine disk parts and blades. At the same time, compared with aluminum and magnesium light alloys, titanium alloys have excellent high temperature performance, and thus have considerable application potential in aero-engine high temperature resistant parts. Conventional near-α type high-temperature titanium alloys have difficulty in coordinating heat and thermal stability, a sharp drop in high-temperature oxidation resistance, and a titanium fire problem in local components. According to the design idea of traditional near–α–type Ti–Al–Sn–Zr–Mo–Si hightemperature titanium alloy, the trace elements Er and Re were added respectively, and Ti–6.5Al–2.5Sn–9Zr–0.5Mo–1Nb–1W–0.25Si–0.1Er and Ti–6.5Al–2.5Sn–9Zr–0.5Mo–1Nb–1W–0.25Si–0.1Re two kinds of high temperature resistant titanium alloys for 650℃ with independent intellectual property rights were designed. The best matching mode for thermal strength, thermal stability and creep resistance is sought from the perspective of regulating the thermal processing process and optimizing the heat treatment system. It provides experimental and theoretical basis for the application of high temperature titanium alloy in the aerospace industry.
Titanium alloy blisk is a typical lightweight and efficient part of advanced aero-engine compressor. While working, the blade and disk of blisk are subjected to quiet different thermal and loading condition, it is an effective mean to improve the weight reduction effect of compressor rotor and to meet more stringent and variable thermodynamic condition through dual-property design instead of the traditional uniform-property design. The feasibility of two gradient heat treatment processes (GHTP), that is, separated-region temperature-controlled GHTP and partial-packed time-controlled GHTP, for manufacturing titanium alloy dual-property blisk is compared, and the microstructural controllability of blade, disk and transition zone is evaluated. The results show that the two processes can form stable and controllable temperature gradient in the transition zone of blisk, and dual microstructure is formed, that is, blade with duplex structure, disk with fine lamellar structure, the area and size of the transition zone is controllable, and the microstructure is gradually changed as well. According to the general contour characteristic, microstructure and performance requirements of the blisk forging, the suitable manufacturing process and corresponding process parameters are applied.
KW–TiC alloy was fabricated through mechanical alloying method and hot rolling process. Compared with KW alloy, the KW–TiC alloy exhibited bending strength of 2500MPa and higher deformation capacity. Both KW–TiC and KW had ductile-to-brittle transition temperature below 250°C. Annealing at 1800°C for 1 hour, no significant equiaxed recrystallization was observed. KW–TiC alloy had the similar structure to KW, but its size was much smaller. The thermal shock resistance of both alloys was characterized by an electron beam facility. Thermal shock tests were conducted at absorbed power densities from 0.44GW/m2 to 0.88GW/m2. After the tests, the KW–TiC and KW alloys showed different crack morphology. However, the existence of TiC reduced the thermal conductivity of KW–TiC alloy, which resulted in the surface melting.
The effect of solid solution temperature (aging at 700℃) in two phase field (α+β) on microstructure and properties of IMI834 titanium alloy forging was studied. Optical and transmission electron microscopy were employed to analyze the microstructure. The tensile properties at room and 600℃ and thermal stability and creep rupture property at 600℃ were tested. The results show that with the increase of solid solution temperature, the content of primary α phase decrease and the size of transformed β and secondary α colonies increase slightly, the tensile plasticity decrease slightly at room and 600℃, the creep rupture property is significantly improved at 600℃. The thermal stability of samples by heat treatment with solid solution in the range of 1000–1030℃ is basically equivalent. The effect of solid solution temperature on properties is closely to element distribution and the size of transformed β and secondary α colonies.
The development of space technology is proposing higher demands on the materials for uses in extreme environment. The present review is divided into five parts, with emphasis focusing on ultrahigh temperature carbides in recent years. Research progresses on mono-carbides, binary carbides, multicomponent high-entropy carbides and their composite materials, in respects of theoretical modeling and prediction, microstructure control and macroscopic proper ties improvement are reviewed. Hardness, toughness and high temperature oxidation resistance of these materials have been enhanced effectively. However, development of highly-efficient fabrication techniques for practical purposes, as well as further investigations on mechanisms of microstructure and properties are still required. Meanwhile, for novel high-entropy carbides, performance improvement by revealing the co-relations of composition and microstructure remains a top priority.
TC21 alloy was carried out on Gleeble–3800 thermal compression simulation tester at temperatures and strain rates ranging of 830–1010℃ and 0.0005–10s–1. Based on the compressed experimental data, taking the hot deformation constitutive relation model derivation of Arrhenius and the hot processing map construction under different instability criterion as the main line of the study, the constitutive model under different hot deformation parameters and the hot processing map under different instability criterion (Gegel, Malas, Prasad, Murty, Semiatin) were obtained. Then, the theoretical basis and prediction results of above five instability criterion were analyzed. By using the theory of hot processing map combining with microstructure, the suitable forming and flowing instability areas were predicted, and hot working processing parameters of TC21 alloy are optimized scientifically and rationally.
The GH4169 superalloy samples were fabricated by selective laser melting. The effects of solution plus double aging heat treatment on the microstructures and tensile properties of selective laser melted GH4169 samples have been investigated. The microstructure of as-deposited GH4169 samples and precipitations after heat treatment were characterized. In the horizontal section (normal to the deposition direction), the as-deposited sample occurs a fine cellular grains structure, while in the vertical section (parallel to the deposition direction), the as-deposited microstructure shows a dendritic structure with a certain epitaxial growth feature. The precipitation of the strengthening phase is inhibited due to the fast cooling rate, thus the microstructure of as-deposited GH4169 sample is characterized by supersaturated austenite matrix γ and inter-dendritic γ + Laves eutectic. After solution plus double aging heat treatment, the dendritic grains and Laves phase dissolved in the austenite matrix. The plate-like δ phase precipitates at the grain boundary, and the discshaped γ"-Ni3Nb phase and the granular γ'-Ni3 (Al, Ti) phase are dispersed inside the grains. The tensile strength of the asdeposited sample are improved after heat treatment. Under the effect of precipitation strengthening, the tensile properties of the heat-treated GH4169 sample at room temperature are comparable to those of forgings.
Combined with the structural characteristics of large aircraft moveable airfoil, a set of whole process flexible automatic drilling scheme is designed. According to the machining way of the robot, a method of quick location by use the cup-and-cone system is proposed to realize the flexible drilling of robot. This paper also studied and built the process of automatic drilling and offline programming used for moveable airfoil. Changeable parameters drilling and breakout process are selected to drill the workpiece with different material, which improved the efficiency and quality of robotic drilling. It is proved that the flexible hole drilling scheme can meet the processing requirement of the product and improve the production efficiency.
The processing technology of high density metal microchannel heat-sink was studied. Based on UV– LIGA technology, the high density mental microchannel plate with 100μm in width and over 500μm in height was fabricated. Then the microchannel plate and the cover plate were packaged. Aimed at the problem that the sealing surface of the high density mental microchannel heat-sink can not be completely bonded when packaging, a novel method based on transition layer compensation was proposed. In order to meet the requirements of air tightness, a shear experiment was carried out in which the shear strength of silver paste, epoxy resin and solder paste were compared. The result shows that the solder paste has the largest shear strength and effect of surface roughness on the bonding strength was further explored. A metal microchannel heat-sink was fabricated based on above technologies. There is no leakage in 2MPa hydraulic seal test, which satisfies the design requirement.
The quality of the rivet holes of the aircraft is critical to the reliability and safety of the aircraft, but the accuracy of the rivet holes is still detected by conventional manual methods, which cannot meet the high precision requirements of modern aircraft for rivet holes. In this paper, through the research of the automatic detection device for the hole quality based on the contact sensor, the mechanical measurement tools such as contact probe and displacement sensor and the automation software such as control and data acquisition system and data processing software are skillfully combined to realize the rivet. The integrated detection function of hole diameter, hole depth, axillary depth and axillary diameter improves the efficiency, accuracy and stability of rivet hole quality detection, and plays a very good role in promoting the contact-type integrated detection of rivet holes.
