Authors: Bogusława Adamczyk-Cieślak, Małgorzata Lewandowska, Jaroslaw Mizera, Krzysztof Jan Kurzydlowski
Abstract: The results obtained in the present study reveal the effect of equal channel angular
extrusion (ECAE) on the grain size and mechanical properties of Al-Li alloys. During 8 passes of ECAE process, coarse grain microstructure in the initial state transforms into ultrafine grained. The
final grain size depends on both total strain applied and Li content in the alloy. Due to the grain refinement the microhardness and yield stress increase by 100%. During compression deformation, the coarse grain alloys exhibit continuous hardening, whereas in the ultrafine-grained alloys, a stagnation of work hardening at the beginning of compression deformation is observed. This behaviour is related to the dynamic recovery of the severely deformed microstructure.
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Authors: Qi Nian Shi, Wei Hao Xiong, Sheng Guo Liu
Abstract: The influence of aging process on microstructures and mechanical properties of a rapid
solidification Aluminum-Lithium alloy has been analyzed in this paper. The results show that the
better aging process is as follows: heating to 170oC for 4 hours and then followed by a final aging at
about 190 oC for 18 hours. A lot of fine participated second phase such as δ′ in matrix and a narrow
participation free band make alloy’s good performance.
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Authors: Sivaswamy Giribaskar, Gouthama, Rajesh Prasad
Abstract: Equal channel angular extrusion (ECAE), involving intense plastic straining under high
applied pressure is generally recognized and extensively studied top down approach for producing
bulk ultra-fine grained (UFG) metallic materials, and even going down in size to the nanometer
range. In this research efforts are made to identify conditional under which grains with size less
than 100 nm form after ECAE. Evolution of microstructure of Al-Li based alloy processed by
ECAE is analyzed using transmission electron microscopy (TEM). Observations on the effect of
precipitates/second phase particles in the sample on the deformation characteristics and their role on
the increased degree of grain fragmentation process is highlighted. Samples of Al-Li based alloy
are solutionized, quenched and aged at different temperatures to obtain well formed precipitate
laths/plates before subjecting to ECAE. During the deformation process these precipitates
disintegrate into fragments and get dispersed into the Al matrix. The fragments of a few
nanometers size bring about drastic changes in the flow as well as the recovery characteristics of
processed samples. Evidence for dynamic recrystallisation taking place during the ECAE
processing is presented. It was observed that optimal thermal treatment leads to more effective
grain refinement and consequently an ultra-fine grained microstructure could be achieved even after
single pass in Al-Li based alloy containing precipitates and second phase particles.
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Authors: Chun Ping Fan, Zi Qiao Zheng, Min Jia, Ji Fa Zhong, Bin Cheng
Abstract: The microstructure, tensile property and fracture toughness of Al-Li alloy 2397-T87 rolled plate were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, tensile and plane-strain fracture toughness tests. The results show that a pronounced texture variation through the plate thickness was found. Near the surface, Goss texture dominated. While in the center of the plate, typical β fiber texture and a scattering of cube texture were observed. And the subsurface layer exhibited a very weak texture. From the center to the subsurface, the fraction of β fiber texture and cube texture decreased. In contrast, the fraction of shear type texture reaching the maximum in subsurface layer increased. The tensile properties in different layers along the thickness direction were inhomogeneous. The strengths near the surface were lower than those in the center. And the through-thickness strength properties variation in the rolling direction was more remarkable than that in the long transverse direction. In the same thickness layer, the fracture toughness and the strengths were anisotropic. The strengths in the rolling direction were higher than those in the long transverse direction and the short transverse direction, and the strengths in the short transverse direction were the lowest. The fracture toughness in L-T orientation was the highest, followed by that in T-L orientation, and the fracture toughness in S-L orientation was the lowest.
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