Ti-48Al-2Mn-2Nb alloy was produced by “centrifugal spray deposition” (CSD), and then hot isostatic pressing (HIP) was employed to remove the porosity formed by CSD. The effects of CSD and HIP processing on the mechanical properties and microstructure of the TiAl alloy were investigated. The results show that the CSD and HIP processing can both improve the strength, plasticity of the TiAl alloy, and the tensile elongation values of the CSD or HIP samples are around 3%, which are better than those of as-cast TiAl alloys in room temperature. Especially, they show more excellent compressive properties at ambient temperature with a compressive ratio of 33.8% and compressive strength of 2210MPa for the CSD samples, and a compressive ratio of 37.8% and compressive strength of 2348MPa for the HIP samples. The CSD processing also improves the fracture toughness of TiAl alloy, which is much higher than that of the HIP processing, while the HIP processing seems to be beneficial the ductility and plasticity as having a duplex structure. The effects of CSD and HIP processing on microstructure and properties of TiAl alloys are discussed to understand the deformation and fracture process of the alloy.
The strengthening effects of the Cu-80 wt.% W (CuW80) alloy and the copper parts in Cu-80wt.% W /Cu (CuW80/Cu) solid contact alloy, which was sintered and infiltrated prepared by powder metallurgy, were investigated. The effects of different compressive deformation on microstructure and properties of the CuW80 were studied. Furthermore, the influences of HextrusionH on copper parts, the carrier material of the solid contact alloy CuW80/Cu were also investigated. The results show that the tungsten and copper phases are closely bonded by physical bond in the form of pseudo-alloy and the copper phase is homogeneously dispersed within the tungsten framework. The hardness of the CuW80 increases with increasing compressive deformation. Especially, the hardness of the copper parts in CuW80/Cu increases remarkably after extrusion and the maximum value can reach 200%. The hardness increases from the inner to the surface and is proportional to the distance departing from the interface of the CuW80 and Cu. TEM observation shows that the dislocation tangles exist, even inside the dislocation cell, in copper grains after extrusion.
Mechanical properties of the TiAl alloy produced by centrifugal spray deposition (CSD), compared to that produced by ingot metallurgy (IM), were investigated at different temperatures from 293 to 973K. The result shows that the ultimate strength, yield strength and plasticity of the CSD TiAl alloys, with excellent compression properties and plasticity, are higher than those of as-cast TiAl alloys at room temperature as well as at high temperature. There exists a critical temperature of 873K in the relationship between strength and temperature, in which strength increases with increasing temperature above 873K. The effects of CSD on mechanical properties of the TiAl alloy are discussed, and the higher strength with moderate ductility achieved is because of the finer lamellar structure got in the CSD processing, and this structure is also believed to be beneficial to ductility.
Tensile experiment of AZ91D magnesium alloy was carried out and serrated flow was apparent throughout the deformation history. Dynamic strain aging (DSA) occurs when the AZ91D magnesium alloy treated by solid solution treatment has been deformed at a set range of strain rates (1.11×10-4 s-1 to1.67×10-3 s-1) and a certain range temperatures (248 K to 423 K). The critical plastic strain εc was observed to increase with increasing strain rates but decrease with increasing temperature. The diffusing activation energy of solute atoms during the DSA occurring in AZ91D magnesium alloy is 140.8 kJ/mol by calculating, which is correspondence match with the diffusing activation energy of Al solute atoms in Mg matrix. Therefore, the micro-mechanism of DSA in the alloy is believed that the Al atoms in solid solution gather around dislocations to form Cottrell solute atmospheres by vacant diffusion and then pin the moving dislocations.
Three-dimensional finite element simulation (3D FES) and experiments were carried out for analyzing the deformation behavior, homogeneity, microstructure and properties of 5052 Al alloy during groove pressing (GP) with two different processing conditions, that is, constrained groove pressing (CGP) and unconstrained groove pressing (UGP). The simulation results show that the values of the equivalent strain and its distribution depend strongly on the constrained conditions. Especially, the equivalent strain and its distribution are inhomogeneous along X direction, with lower strain regions located at both ends and larger strain regions with periodic variation located at intermediate section. CGP results in a higher accumulative rate of equivalent strain than that of UGP. The average strain is equal to the theoretical strain for CGP, but it is much lower than its theoretical strain for UGP. The experimental results show that grain sizes of 5052 Al alloy can be refined significantly by CGP or UGP, while CGP has a higher rate of grain refinement and finer grains than that of UGP. And the results of microhardness confirmed the prediction of 3D FES.
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