The doleritic dykes present in the Téra-Ayorou pluton crosscut the basement of the Nigerien Liptako and are part of the system of intrusive mafic dykes in the Paleoproterozoic domain of the Léo-Man ridge. In...The doleritic dykes present in the Téra-Ayorou pluton crosscut the basement of the Nigerien Liptako and are part of the system of intrusive mafic dykes in the Paleoproterozoic domain of the Léo-Man ridge. In the previous work, emphasis was placed on the petrology, geochemistry and geochronology of the Liptako doleritic dykes. This study aims to analyze the tectonic style of intrusive doleritic dykes in the Téra-Ayorou pluton. The characterization of the deformation which affected the doleritic dykes of the Téra-Ayorou pluton is important for the evaluation of their economic potential. To this end, measurements of tectonic structure planes were taken in the field, and samples were taken from the chilled margin and cores of dolerite dykes, before being processed in the laboratory. Analysis of the tectonic structures collected revealed a brittle tectonic pattern, characterizing a phase of deformation subdivided into two episodes D1 and D2. Episode D1, with its subvertically dipping normal faults and simple N70˚ - N110˚ fractures, is compatible with N-S extension. On the other hand, episode D2, which created shear corridors by reactivation of pre-existing fractures and oriented N150˚ - N170˚, is associated with a WSW-ENE extension. These results open up prospects for the exploration of gold, uranium mineralization and diamonds in the north-west of Niger.展开更多
The finite deformation structures recorded in the Essakane area, located in the northeast corner of Burkina Faso, highlight three major compressive deformation phases, successively named D1, D2, and D3. The D1 event p...The finite deformation structures recorded in the Essakane area, located in the northeast corner of Burkina Faso, highlight three major compressive deformation phases, successively named D1, D2, and D3. The D1 event phase, trending NE-SW, is characterised by P1 folds and S1 axial plane schistosity. The D2 phase trending NW-SE is characterised by folds P2, schistosity (S2) and shear (C) planes. And the D3 phase trending NNE-SSW to N-S is characterised by P3 folds, crenulation microfolds and S3 spaced schistosity. It has also been noted that gold mineralizations are mainly hosted in quartz, carbonate, pyrite, and arsenopyrite veins. Structural interpretation indicates that these veins are organized into lenticular bodies that were formed during the first two deformation phases (D1 and D2). This suggests a strong structural control typical of orogenic gold concentrations.展开更多
TiC nanoparticle-reinforced Mg−4Zn−0.5Ca matrix nanocomposites were processed by combining multidirectional forging(MDF)and extrusion(EX).The grain size of the nanocomposite after MDF+EX multi-step deformation was sig...TiC nanoparticle-reinforced Mg−4Zn−0.5Ca matrix nanocomposites were processed by combining multidirectional forging(MDF)and extrusion(EX).The grain size of the nanocomposite after MDF+EX multi-step deformation was significantly decreased compared with that processed only by MDF.The average size of the recrystallized grains gradually increased after EX with increasing the number of MDF passes at 270℃.However,the grain size significantly decreased by MDF processing at 310℃.Both fine and coarse MgZn2 phases appeared in the(MDF+EX)-processed nanocomposites,and their volume fractions gradually increased with increasing the number of MDF passes before EX.Ultrahigh tensile properties(yield strength of^404 MPa,ultimate tensile strength of^450.3 MPa and elongation of^5.2%)were obtained in the nanocomposite after three MDF passes at 310℃ followed by EX.This was attributed to the refinement of the recrystallized grains,together with the improved Orowan strengthening provided by the precipitated MgZn2 particles that were generated by MDF+EX multi-step deformation.展开更多
An austenitic stainless steel with 6 wt% Si and multiple secondary phases was produced with the aim to achieve enhanced plasticity during hot deformation.The micro structure of the steel after fracture was characteriz...An austenitic stainless steel with 6 wt% Si and multiple secondary phases was produced with the aim to achieve enhanced plasticity during hot deformation.The micro structure of the steel after fracture was characterized via electron back-scattered diffraction,transmission Kikuchi diffraction and scanning transmission electron microscopy.From the tail of the gage to the necking region,the microstructure of the material evolved from low-angle grain boundaries(LAGB s) to mixtures of LAGBs and high-angle grain boundaries(HAGBs),and fine equiaxed recrystallized grains.The elongation to failure in the tensile test exceeds 167%.During the hot deformation,continuous dynamic recrystallization of the austenitic matrix was promoted by the multiple secondary phases.The dislocations introduced by the secondary phases were rearranged and continuously transformed into HAGBs.The initially coarse grains(30.5 μm) were refined into ultra-fine equiaxed grains(1 μm),which contributed significantly the enhanced plasticity during hot deformation of the steel.In the necking area of the sample,twins were nucleated in the stress concentration regions and accommodated the local strain by discontinuous dynamic recrystallization,which was also beneficial to improving the plasticity.展开更多
On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests o...On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests of AC16 asphalt mixtures were conducted to validate this new developed model. Parameters of new developed model were obtained by a nonlinear regression analysis of test data, and then permanent strains and flow number of each mixture were calculated. The experimental results prove that the new developed model can well describe three phases permanent deformation of asphalt mixture under repeated load and it can be used for pavement mechanical analysis and rutting prediction.展开更多
文摘The doleritic dykes present in the Téra-Ayorou pluton crosscut the basement of the Nigerien Liptako and are part of the system of intrusive mafic dykes in the Paleoproterozoic domain of the Léo-Man ridge. In the previous work, emphasis was placed on the petrology, geochemistry and geochronology of the Liptako doleritic dykes. This study aims to analyze the tectonic style of intrusive doleritic dykes in the Téra-Ayorou pluton. The characterization of the deformation which affected the doleritic dykes of the Téra-Ayorou pluton is important for the evaluation of their economic potential. To this end, measurements of tectonic structure planes were taken in the field, and samples were taken from the chilled margin and cores of dolerite dykes, before being processed in the laboratory. Analysis of the tectonic structures collected revealed a brittle tectonic pattern, characterizing a phase of deformation subdivided into two episodes D1 and D2. Episode D1, with its subvertically dipping normal faults and simple N70˚ - N110˚ fractures, is compatible with N-S extension. On the other hand, episode D2, which created shear corridors by reactivation of pre-existing fractures and oriented N150˚ - N170˚, is associated with a WSW-ENE extension. These results open up prospects for the exploration of gold, uranium mineralization and diamonds in the north-west of Niger.
文摘The finite deformation structures recorded in the Essakane area, located in the northeast corner of Burkina Faso, highlight three major compressive deformation phases, successively named D1, D2, and D3. The D1 event phase, trending NE-SW, is characterised by P1 folds and S1 axial plane schistosity. The D2 phase trending NW-SE is characterised by folds P2, schistosity (S2) and shear (C) planes. And the D3 phase trending NNE-SSW to N-S is characterised by P3 folds, crenulation microfolds and S3 spaced schistosity. It has also been noted that gold mineralizations are mainly hosted in quartz, carbonate, pyrite, and arsenopyrite veins. Structural interpretation indicates that these veins are organized into lenticular bodies that were formed during the first two deformation phases (D1 and D2). This suggests a strong structural control typical of orogenic gold concentrations.
基金Projects(51771129,51401144,51771128)supported by the National Natural Science Foundation of China,Project supported by the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi,ChinaProjects(2015021067,201601D011034)supported by the Natural Science Foundation of Shanxi Province,China+1 种基金Project(201703D421039)supported by the International Cooperation in Shanxi,ChinaProject supported by the China Scholarship Council。
文摘TiC nanoparticle-reinforced Mg−4Zn−0.5Ca matrix nanocomposites were processed by combining multidirectional forging(MDF)and extrusion(EX).The grain size of the nanocomposite after MDF+EX multi-step deformation was significantly decreased compared with that processed only by MDF.The average size of the recrystallized grains gradually increased after EX with increasing the number of MDF passes at 270℃.However,the grain size significantly decreased by MDF processing at 310℃.Both fine and coarse MgZn2 phases appeared in the(MDF+EX)-processed nanocomposites,and their volume fractions gradually increased with increasing the number of MDF passes before EX.Ultrahigh tensile properties(yield strength of^404 MPa,ultimate tensile strength of^450.3 MPa and elongation of^5.2%)were obtained in the nanocomposite after three MDF passes at 310℃ followed by EX.This was attributed to the refinement of the recrystallized grains,together with the improved Orowan strengthening provided by the precipitated MgZn2 particles that were generated by MDF+EX multi-step deformation.
文摘An austenitic stainless steel with 6 wt% Si and multiple secondary phases was produced with the aim to achieve enhanced plasticity during hot deformation.The micro structure of the steel after fracture was characterized via electron back-scattered diffraction,transmission Kikuchi diffraction and scanning transmission electron microscopy.From the tail of the gage to the necking region,the microstructure of the material evolved from low-angle grain boundaries(LAGB s) to mixtures of LAGBs and high-angle grain boundaries(HAGBs),and fine equiaxed recrystallized grains.The elongation to failure in the tensile test exceeds 167%.During the hot deformation,continuous dynamic recrystallization of the austenitic matrix was promoted by the multiple secondary phases.The dislocations introduced by the secondary phases were rearranged and continuously transformed into HAGBs.The initially coarse grains(30.5 μm) were refined into ultra-fine equiaxed grains(1 μm),which contributed significantly the enhanced plasticity during hot deformation of the steel.In the necking area of the sample,twins were nucleated in the stress concentration regions and accommodated the local strain by discontinuous dynamic recrystallization,which was also beneficial to improving the plasticity.
基金Funded by the National Natural Science Foundation of China (No.50878054)
文摘On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests of AC16 asphalt mixtures were conducted to validate this new developed model. Parameters of new developed model were obtained by a nonlinear regression analysis of test data, and then permanent strains and flow number of each mixture were calculated. The experimental results prove that the new developed model can well describe three phases permanent deformation of asphalt mixture under repeated load and it can be used for pavement mechanical analysis and rutting prediction.
