Microstructural features of a duplex-phase Zr-2.5Nb alloy were investigated in detail using electron channeling contrast （ECC） imaging and electron backscatter diffraction （EBSD） technique in an emission gun scann...Microstructural features of a duplex-phase Zr-2.5Nb alloy were investigated in detail using electron channeling contrast （ECC） imaging and electron backscatter diffraction （EBSD） technique in an emission gun scanning electron microscope （FEGSEM）. The excellent resolution provided by the FEGSEM promises the combined utilization of both techniques to be quite adequate for characterizing the duplex-phase microstructures. Results show that the microstructure of the Zr-2.5Nb alloy is composed of bulk a grains （majority） in equiaxed or plate shape and thin 13 films （minority） surrounding the bulk grains, with their average grain size and thickness measured to be 1.4 prn and 72 nm, respectively. Analyses on a-grain boundaries reveal a number of low angle boundaries, most of which belong to deformation-induced dislocation boundaries. Measurements on relative propor- tions of various Burgers boundaries suggest very weak （if any） variant selection during 13 ~ a cooling, which should be re- lated to deformation-induced higher nucleation rate of a phases. Compared to earlier attempts, more satisfactory indexing of fine β phases （down to nanoscale） is attained by the FEGSEM-based EBSD. Examples are presented to clearly reveal well-obeyed Burgers orientation relationships between adjacent α and β phases. Finally, it is deduced that continuing applica- tion of the FEGSEM-based EBSD to duplex-phase Zr alloys could help clarify controversies like the deformation priority of the two phases.展开更多
Microstructures of a duplex-phase Zr-2.5Nb alloy treated by pulsed laser were characterized by electron backscatter diffraction （EBSD） and electron channeling contrast （ECC） imaging techniques. Major attention has...Microstructures of a duplex-phase Zr-2.5Nb alloy treated by pulsed laser were characterized by electron backscatter diffraction （EBSD） and electron channeling contrast （ECC） imaging techniques. Major attention has been paid to non-equilibrium hybrid microstructure consisting of both prior a and β phases, and a plates transformed from new β phases to probe α→β transformation characteristics in the alloy. The origin of the hybrid microstructure is attributed to the specific thermodynamic conditions induced by the pulsed laser treatment. ECC observation shows that newly formed [3 phases during laser heating prefer to nucleate and grow at the expense of edges of prior α grains rather than their interiors. EBSD analyses further reveal that orientations of the new β phases are not determined by the prior a grains according to the Burgers relationship but maintain those of the prior β phases in an epitaxial growth way.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.5140104051371202+3 种基金51531005&51421001)China Postdoctoral Science Foundation(Grant No.2015M572446)Postdoctoral Science Foundation of Chongqing(Grant No.Xm2015003)Scientific and Technological Research Program of Chongqing Municipal Education Commission(Grant No.KJ1500901)
文摘Microstructural features of a duplex-phase Zr-2.5Nb alloy were investigated in detail using electron channeling contrast （ECC） imaging and electron backscatter diffraction （EBSD） technique in an emission gun scanning electron microscope （FEGSEM）. The excellent resolution provided by the FEGSEM promises the combined utilization of both techniques to be quite adequate for characterizing the duplex-phase microstructures. Results show that the microstructure of the Zr-2.5Nb alloy is composed of bulk a grains （majority） in equiaxed or plate shape and thin 13 films （minority） surrounding the bulk grains, with their average grain size and thickness measured to be 1.4 prn and 72 nm, respectively. Analyses on a-grain boundaries reveal a number of low angle boundaries, most of which belong to deformation-induced dislocation boundaries. Measurements on relative propor- tions of various Burgers boundaries suggest very weak （if any） variant selection during 13 ~ a cooling, which should be re- lated to deformation-induced higher nucleation rate of a phases. Compared to earlier attempts, more satisfactory indexing of fine β phases （down to nanoscale） is attained by the FEGSEM-based EBSD. Examples are presented to clearly reveal well-obeyed Burgers orientation relationships between adjacent α and β phases. Finally, it is deduced that continuing applica- tion of the FEGSEM-based EBSD to duplex-phase Zr alloys could help clarify controversies like the deformation priority of the two phases.
基金supported by the National Natural Science Foundation of China(Grant No.51401040)China Postdoctoral Science Foundation(Grant No.2015M572446)+1 种基金Postdoctoral Science Foundation of Chongqing(Grant No.Xm2015003)Scientific and Technological ResearchProgram of Chongqing Municipal Education Commission(Grant No.KJ1500901)
文摘Microstructures of a duplex-phase Zr-2.5Nb alloy treated by pulsed laser were characterized by electron backscatter diffraction （EBSD） and electron channeling contrast （ECC） imaging techniques. Major attention has been paid to non-equilibrium hybrid microstructure consisting of both prior a and β phases, and a plates transformed from new β phases to probe α→β transformation characteristics in the alloy. The origin of the hybrid microstructure is attributed to the specific thermodynamic conditions induced by the pulsed laser treatment. ECC observation shows that newly formed [3 phases during laser heating prefer to nucleate and grow at the expense of edges of prior α grains rather than their interiors. EBSD analyses further reveal that orientations of the new β phases are not determined by the prior a grains according to the Burgers relationship but maintain those of the prior β phases in an epitaxial growth way.
