Authors: Guo Qing Chen, S.H. Ji, Wen Long Zhou, C.W. Wu, Jian Ting Guo, Z.H. Huang
Abstract: NiAl-based alloy is a promising material applied in the fields of aeronautic and astronautic
instruments. In the paper the compression deformation behavior and microstructure evolution of
NiAl-Cr(Mo)-Hf alloy at elevated temperature were studied. The results demonstrate that the alloy
behaves good formability in the temperature ranging from 1320°C to 1360°C, in which the maximum
initial strain rate is about 8.3×10-4s-1 and the maximum deformation resistance is lower than 40MPa.
During compression at temperature between 1250°C and 1300°C the flow stress increased sharply
with the increasing of the deformation degree. When compression deformation at 1320°C~1360°C,
the flow stress decreased obviously and the flow stress decreased slightly after reached the maximum
value. By analyzing the microstructure evolution during compression it can be concluded that
as-casting microstructure was improved in deformation. The grains were refined and the brittle phases
of lamellar Cr(Mo) existing at NiAl matrix were broken. The porosities in as-casting material were
eliminated during compression and the density of the material increased. The fracture toughness of
the alloy increased from 6.4MPa·m1/2 to 9.8MPa·m1/2 after compression.
457
Authors: Feng Jian Shi, Tao Xu, Sheng Lu, Lei Gang Wang
Abstract: In this paper, effective strain and load were simulated by rigid-plastic finite element method (FEM) during cyclic channel die compression (CCDC) with route A, and the optical microstructure was observed. The results show that large strain can be accumulated in the material by CCDC. The load variation includes two stages, slowly linear increase and rapid increase. At the end of the CCDC, the compression load rises rapidly. Apart from the edges of the specimen, the effective strain is higher in the central region and lower at the surrounding region. The effective strain gradient increases with the number of compression. Grain refinement at the central zone is faster due to the strain inhomogeneity. But the peripheral zone is also refined with the number of CCDC. This illustrates CCDC is a promising method for producing bulk ultra-fine grained materials.
1300
Authors: Jia Le Sun, Rui Chun Li, Gao Feng Quan, Zhao Ming Liu
Abstract: The microstructure, surface morphology, compression properties, deformation behaviour and strain hardening exponent of as-cast and as-extruded AZ31 Mg alloy after different annealing treatments were investigated. The results show that the compression properties are great different between cast AZ31 alloy and extruded AZ31 alloy. Extruded AZ31 alloy is discontinuous yield and on the surface no signs of damage have been observed; on the contrast, cast AZ31 alloy is continuous yield and shows wavy patterns, and the surface cracks can be easily found. In addition, there is a linear relationship between the strain hardening exponent in first deformation stage and the yield ratio. Further more, the twinning mechanism plays very different role in cast AZ31 alloy and extruded AZ31 alloy.
1960
Authors: Bao Guo Yuan, Qiang Chen, Hai Ping Yu, Ping Li, Ke Min Xue, Chun Feng Li
Abstract: Compression tests of the hydrogenated Ti6Al4V0.2H alloy were carried out using an Instron 5569 machine at room temperature. True stress-strain curves of the hydrogenated Ti6Al4V0.2H alloy under different compressive strains were obtained. Microstructure evolution of the hydrogenated Ti6Al4V0.2H alloy during the process of compression was investigated by optical microscopy and transmission electron microscopy. Results show that true stress-true strain curves of Ti6Al4V0.2H alloy have good repeatability. The deformation of grains, the dislocation density and slipping evolution during the process of compression are discussed.
517
Authors: Jun Fan, Lei Gang Wang
Abstract: The filling capability is important for forging die design, which influences the quality and life of the die. To obtain the know-how of the deficiency for the filling capability, numerical simulation was performed to analyze the hot compression of Ti75 alloy with DEFORM-3D. In the simulation, the reducing height and work-piece dimensions remain the same. We obtained the results including the process of hot compression, the forming behavior of the work-piece and the effect of work-piece dimensions on the distribution of the stress and strain.
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