The microstructures and hardness of pure Al samples subjected to plastic deformation with different tem- peratures and strain rates were investigated. The results showed that the strain-induced grain refinement is sig...The microstructures and hardness of pure Al samples subjected to plastic deformation with different tem- peratures and strain rates were investigated. The results showed that the strain-induced grain refinement is significantly benefited by increasing strain rate and reducing deformation temperature. The saturated size of refined subgrains in Al can be as small as about 240 nm in cryogenic dynamic plastic deformation (DPD). Grain boundaries of the DPD Al samples are low-angle boundaries due to suppression of dynamic recovery during deformation. Agreement of the measured hardness with the empirical Hall-Petch relation extrapolated from the coarse-grained Al implies that the low-angle boundaries can contribute to strengthening as effective as the conventional grain boundaries.展开更多
The compression behavior of a Ti-23.1 Nb-2.0 Zr-1.00(at.%)alloy was investigated at strain rates from 0.1 s_(-1) to 1000 s_(-1) and temperatures from 100℃to 200℃on a Gleeble 3800 system and Split Hopkinson Pressure ...The compression behavior of a Ti-23.1 Nb-2.0 Zr-1.00(at.%)alloy was investigated at strain rates from 0.1 s_(-1) to 1000 s_(-1) and temperatures from 100℃to 200℃on a Gleeble 3800 system and Split Hopkinson Pressure Bar(SHPB)compressive tester.Optical microscopy,electron backscatter diffraction(EBSD),Xray diffraction(XRD)and transmission electron microscopy(TEM)were employed to characterize the microstructure evolution during the deformation.Numerous deformation phenomena,including dislocation slip,twinning of both{332}{113)and{112}{111}modes,stress-inducedα"martensite(SIMα")and stress-inducedω(SIω)transformations,were observed.The preferred activation of twinning and SIωtransfo rmations was observed in the sample compressed at lower temperatures and/or higher strain rates.The underlying mechanism is that twinning and stress induced phase transfo rmations are attribute to higher stress concentrations atβgrain boundaries and additional energy supplied by a higher strain rate,as well as high stacking fault energy because of higher temperature.展开更多
The high temperature deformation behavior and microstructures evolution of TC17 alloy in the temperature range of 820°C - 930°C, strain rate range of 0.01 s-1 - 10 s-1 and height direction reduction of 20% -...The high temperature deformation behavior and microstructures evolution of TC17 alloy in the temperature range of 820°C - 930°C, strain rate range of 0.01 s-1 - 10 s-1 and height direction reduction of 20% - 80% have been studied by hot compressing testing. The microstructures of TC17 alloy were observed and analyzed using Olympus/PMG3 optical microscope. The flow stresses were correlated with strain rate and the temperature by the constitutive equation. The results show that the flow stress of TC17 alloy increase quickly with the strain, then decrease with a steady value. The deformation activation energy obtained in the α + β region for TC17 was 407 kJ/mol, and in the β region was 155 kJ/mol. It was also found that the degree of dynamic globularization of α phase increases with increasing strains, increasing temperature and decreasing strain rate in α + β region, the dynamic re-crystallization is obvious at low strain rate and dynamic recovery is obvious at high strain rate in β region.展开更多
基金support from the National Natural Science Foundation of China (Grants Nos. 50971122, 50431010,50621091, 50890171)Shenyang Science & Technology Project (No. 1071107-1-00)the Ministry of Scienceand Technology of China (2005CB623604)
文摘The microstructures and hardness of pure Al samples subjected to plastic deformation with different tem- peratures and strain rates were investigated. The results showed that the strain-induced grain refinement is significantly benefited by increasing strain rate and reducing deformation temperature. The saturated size of refined subgrains in Al can be as small as about 240 nm in cryogenic dynamic plastic deformation (DPD). Grain boundaries of the DPD Al samples are low-angle boundaries due to suppression of dynamic recovery during deformation. Agreement of the measured hardness with the empirical Hall-Petch relation extrapolated from the coarse-grained Al implies that the low-angle boundaries can contribute to strengthening as effective as the conventional grain boundaries.
基金financially supported by the internal funding source from University of Shanghai for Science and Technology,Frontier and Key Projects of the Chinese Academy of Sciences(No.QYZDJ-SSW-JSC031-01)the China National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact(No.6142902190501)。
文摘The compression behavior of a Ti-23.1 Nb-2.0 Zr-1.00(at.%)alloy was investigated at strain rates from 0.1 s_(-1) to 1000 s_(-1) and temperatures from 100℃to 200℃on a Gleeble 3800 system and Split Hopkinson Pressure Bar(SHPB)compressive tester.Optical microscopy,electron backscatter diffraction(EBSD),Xray diffraction(XRD)and transmission electron microscopy(TEM)were employed to characterize the microstructure evolution during the deformation.Numerous deformation phenomena,including dislocation slip,twinning of both{332}{113)and{112}{111}modes,stress-inducedα"martensite(SIMα")and stress-inducedω(SIω)transformations,were observed.The preferred activation of twinning and SIωtransfo rmations was observed in the sample compressed at lower temperatures and/or higher strain rates.The underlying mechanism is that twinning and stress induced phase transfo rmations are attribute to higher stress concentrations atβgrain boundaries and additional energy supplied by a higher strain rate,as well as high stacking fault energy because of higher temperature.
文摘The high temperature deformation behavior and microstructures evolution of TC17 alloy in the temperature range of 820°C - 930°C, strain rate range of 0.01 s-1 - 10 s-1 and height direction reduction of 20% - 80% have been studied by hot compressing testing. The microstructures of TC17 alloy were observed and analyzed using Olympus/PMG3 optical microscope. The flow stresses were correlated with strain rate and the temperature by the constitutive equation. The results show that the flow stress of TC17 alloy increase quickly with the strain, then decrease with a steady value. The deformation activation energy obtained in the α + β region for TC17 was 407 kJ/mol, and in the β region was 155 kJ/mol. It was also found that the degree of dynamic globularization of α phase increases with increasing strains, increasing temperature and decreasing strain rate in α + β region, the dynamic re-crystallization is obvious at low strain rate and dynamic recovery is obvious at high strain rate in β region.
