A thermally induced hexagonal close-packed(HCP)to face-centered cubic(FCC)phase transition was investigated in anα-type Ti35 alloy with twinned structure by in situ heating transmission electron microscopy(TEM)and ab...A thermally induced hexagonal close-packed(HCP)to face-centered cubic(FCC)phase transition was investigated in anα-type Ti35 alloy with twinned structure by in situ heating transmission electron microscopy(TEM)and ab initio calculations.TEM observations indicated that the HCP to FCC phase transition occurred both within matrix/twin and at the twin boundaries in the thinner region of the TEM film,and the FCC-Ti precipitated as plates within the matrix/twin,while as equiaxed cells at twin boundaries.The crystallographic orientation relationship between HCP-Ti and FCC-Ti can be described as:{111}FCC//{0002}HCP and<110>FCC//<1210>HCP.The HCP to FCC phase transition was accomplished by forming an intermediate state with a BB stacking sequence through the slip of partial dislocations.The formation of such FCC-Ti may be related to the thermal stress and temperature.Ab initio calculations showed that the formation of FCC-Ti may also be related to the contamination of interstitial atoms such as oxygen.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
基金supported by the Natural Science Foundation of Shanghai(Grant No.21ZR1445100)the National Natural Science Foundation of China(Grant No.52271108)+2 种基金the Foundation of Xi'an Key Laboratory of High-Performance Titanium Alloy(Grant No.NIN-HTL-2022-02)financial support from the Frontier and Key Projects of the Chinese Academy of Sciences(Grant No.QYZDJ-SSW-JSC031-01)financial support from Xi’an Science and Technology Plan Project(Grant No.2020YZ0028).
文摘A thermally induced hexagonal close-packed(HCP)to face-centered cubic(FCC)phase transition was investigated in anα-type Ti35 alloy with twinned structure by in situ heating transmission electron microscopy(TEM)and ab initio calculations.TEM observations indicated that the HCP to FCC phase transition occurred both within matrix/twin and at the twin boundaries in the thinner region of the TEM film,and the FCC-Ti precipitated as plates within the matrix/twin,while as equiaxed cells at twin boundaries.The crystallographic orientation relationship between HCP-Ti and FCC-Ti can be described as:{111}FCC//{0002}HCP and<110>FCC//<1210>HCP.The HCP to FCC phase transition was accomplished by forming an intermediate state with a BB stacking sequence through the slip of partial dislocations.The formation of such FCC-Ti may be related to the thermal stress and temperature.Ab initio calculations showed that the formation of FCC-Ti may also be related to the contamination of interstitial atoms such as oxygen.
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.
