The flow stress behavior and microstructural evolution in as rolled AZ91 alloy were studied by tensile test at temperature ranging from 573 K to 698 K and with initial strain rate of 10-31s-1. The results show that th...The flow stress behavior and microstructural evolution in as rolled AZ91 alloy were studied by tensile test at temperature ranging from 573 K to 698 K and with initial strain rate of 10-31s-1. The results show that the activation energy of the AZ91 alloy is 96 kJ/mol and the stress exponent is 3.5.Grain refinement is observed during hot deformation. It is found that grain refinement is due to dynamic recrystallization, but grain size is decreased with increasing Zener-Hollomon parameter. The deformation mechanism is dislocation cross-slip, dislocation climbs and twin intersections, which are probably suitable to the development of substructures. Twins always exist in matrix whether they are at high temperature or at low temperature. Strain induced precipitation of Mg17Al12 occurs in the AZ91 alloy and stabilizes the subgrain boundaries.展开更多
Sliding planes of PTFE are commonly used because of their excellent tribological properties. However, especially in cases of high contact pressures, PTFE suffers from its comparatively poor mechanical properties. This...Sliding planes of PTFE are commonly used because of their excellent tribological properties. However, especially in cases of high contact pressures, PTFE suffers from its comparatively poor mechanical properties. This paper presents a sliding construction developed within an innovative experimental test-setup to enable experimental investigation of large-scale concrete members subjected to punching shear. To fulfill the special demands of the new test-setup, greased, only 0.5 mm thin sheets of PTFE were used to minimize friction between the bearing construction and the test specimen. This highly effective sliding construction leads to a dynamic friction coefficient μ<sub>d,max</sub> between 0.0065 and 0.0035 while the static friction coefficient μ<sub>s</sub> remains below 0.0048. Simultaneously, compressive axial stresses of more than 60 MPa occur. The paper highlights major aspects of the sliding plane’s development and demonstrates its sliding abilities.展开更多
The high strain rate superplastic deformation properties and characteristics of a rolled AZ91 magnesium alloy at temperatures ranging from 623 to 698 K（0.67Tm-0.76Tm） and high strain rates ranging from 10^-3 to 1 s^...The high strain rate superplastic deformation properties and characteristics of a rolled AZ91 magnesium alloy at temperatures ranging from 623 to 698 K（0.67Tm-0.76Tm） and high strain rates ranging from 10^-3 to 1 s^-1 were investigated.The rolled AZ91 magnesium alloy possesses excellent superplasticity with the maximum elongation of 455% at 623 K and a strain rate of 10-3 s-1,and its strain rate sensitivity m is high up to 0.64.The dominant deformation mechanism responsible for the high strain rate superplasticity is still grain boundary sliding（GBS）,and the dislocation creep mechanism is considered as the main accommodation mechanism.展开更多
基金Project(0 2SL0 0 2 )supportedbyShanghaiScienceandTechnologyCommittee China
文摘The flow stress behavior and microstructural evolution in as rolled AZ91 alloy were studied by tensile test at temperature ranging from 573 K to 698 K and with initial strain rate of 10-31s-1. The results show that the activation energy of the AZ91 alloy is 96 kJ/mol and the stress exponent is 3.5.Grain refinement is observed during hot deformation. It is found that grain refinement is due to dynamic recrystallization, but grain size is decreased with increasing Zener-Hollomon parameter. The deformation mechanism is dislocation cross-slip, dislocation climbs and twin intersections, which are probably suitable to the development of substructures. Twins always exist in matrix whether they are at high temperature or at low temperature. Strain induced precipitation of Mg17Al12 occurs in the AZ91 alloy and stabilizes the subgrain boundaries.
文摘Sliding planes of PTFE are commonly used because of their excellent tribological properties. However, especially in cases of high contact pressures, PTFE suffers from its comparatively poor mechanical properties. This paper presents a sliding construction developed within an innovative experimental test-setup to enable experimental investigation of large-scale concrete members subjected to punching shear. To fulfill the special demands of the new test-setup, greased, only 0.5 mm thin sheets of PTFE were used to minimize friction between the bearing construction and the test specimen. This highly effective sliding construction leads to a dynamic friction coefficient μ<sub>d,max</sub> between 0.0065 and 0.0035 while the static friction coefficient μ<sub>s</sub> remains below 0.0048. Simultaneously, compressive axial stresses of more than 60 MPa occur. The paper highlights major aspects of the sliding plane’s development and demonstrates its sliding abilities.
基金supported by the National Natural Science Foundation of China(No.50674067).
文摘The high strain rate superplastic deformation properties and characteristics of a rolled AZ91 magnesium alloy at temperatures ranging from 623 to 698 K（0.67Tm-0.76Tm） and high strain rates ranging from 10^-3 to 1 s^-1 were investigated.The rolled AZ91 magnesium alloy possesses excellent superplasticity with the maximum elongation of 455% at 623 K and a strain rate of 10-3 s-1,and its strain rate sensitivity m is high up to 0.64.The dominant deformation mechanism responsible for the high strain rate superplasticity is still grain boundary sliding（GBS）,and the dislocation creep mechanism is considered as the main accommodation mechanism.
