Fatigue strength,crack initiation and propagation behavior of rolled AZ31B magnesium alloy plate were investigated. Axial tension-compression fatigue tests were carried out with cylindrical smooth specimens.Two types ...Fatigue strength,crack initiation and propagation behavior of rolled AZ31B magnesium alloy plate were investigated. Axial tension-compression fatigue tests were carried out with cylindrical smooth specimens.Two types of specimens were machined with the loading axis parallel(L-specimen)and perpendicular(T-specimen)to rolling direction.Monotonic compressive 0.2%proof stress,tensile strength and tensile elongation were similar for both specimens.On the other hand,monotonic tensile 0.2%proof stress of the L-specimen was slightly higher than that of the T-specimen.Moreover,monotonic compressive 0.2%proof stresses were lower than tensile ones for both specimens.The fatigue strengths of 107cycles of the L-and T-specimens were 95 and 85 MPa,respectively. Compared with the monotonic compressive 0.2%proof stresses,the fatigue strengths were higher for both specimens.In other words, the fatigue crack did not initiate and propagate even though deformation twins were formed in compressive stress under the cyclic tension-compression loading.The fatigue crack initiated at early stage of the fatigue life in low cycle regime regardless of specimen direction.The crack growth rate of the L-specimen was slightly lower than of the T-specimen.Consequently,the fatigue lives of the L-specimen were longer than those of the T-specimen in low cycle regime.展开更多
In this work, we study how an epitaxial laser-like(or superluminescent diode-like) structure is modified by intentional changes of the substrate misorientation in the range of 0.5°–2.6°. The 40 μm × ...In this work, we study how an epitaxial laser-like(or superluminescent diode-like) structure is modified by intentional changes of the substrate misorientation in the range of 0.5°–2.6°. The 40 μm × 40 μm test structure with misorientation profiling was fabricated using multilevel photolithography and dry-etching. The local structural parameters were measured by synchrotron radiation microbeam X-ray diffraction, with the sampling area of below 1 μm × 1 μm. We directly obtained the relation between the misorientation and indium content in the quantum well, changing from 9% to 18%, with a high resolution(small misorientation step). We also show a good agreement of local photoluminescence emission wavelength with simulation of transition energy based on synchrotron radiation microbeam X-ray diffraction(SR-XRD) data and estimated Stokes shift. We observe that the substrate misorientation influences also the In Ga N waveguide and Al Ga N cladding composition. Still, we showed through simulation of the optical confinement factor of a full laser diode structure that good light guiding properties should be preserved in the whole misorientation range studied here. This proves the usefulness of misorientation modification in applications like broadband superluminescent diodes or multicolor laser arrays.展开更多
文摘Fatigue strength,crack initiation and propagation behavior of rolled AZ31B magnesium alloy plate were investigated. Axial tension-compression fatigue tests were carried out with cylindrical smooth specimens.Two types of specimens were machined with the loading axis parallel(L-specimen)and perpendicular(T-specimen)to rolling direction.Monotonic compressive 0.2%proof stress,tensile strength and tensile elongation were similar for both specimens.On the other hand,monotonic tensile 0.2%proof stress of the L-specimen was slightly higher than that of the T-specimen.Moreover,monotonic compressive 0.2%proof stresses were lower than tensile ones for both specimens.The fatigue strengths of 107cycles of the L-and T-specimens were 95 and 85 MPa,respectively. Compared with the monotonic compressive 0.2%proof stresses,the fatigue strengths were higher for both specimens.In other words, the fatigue crack did not initiate and propagate even though deformation twins were formed in compressive stress under the cyclic tension-compression loading.The fatigue crack initiated at early stage of the fatigue life in low cycle regime regardless of specimen direction.The crack growth rate of the L-specimen was slightly lower than of the T-specimen.Consequently,the fatigue lives of the L-specimen were longer than those of the T-specimen in low cycle regime.
基金Japan Society for the Promotion of Science(JP15H05732, JP16H02332, JP16H06426)Fundacja na rzecz Nauki Polskiej (TEAM TECH/2017-4/24)。
文摘In this work, we study how an epitaxial laser-like(or superluminescent diode-like) structure is modified by intentional changes of the substrate misorientation in the range of 0.5°–2.6°. The 40 μm × 40 μm test structure with misorientation profiling was fabricated using multilevel photolithography and dry-etching. The local structural parameters were measured by synchrotron radiation microbeam X-ray diffraction, with the sampling area of below 1 μm × 1 μm. We directly obtained the relation between the misorientation and indium content in the quantum well, changing from 9% to 18%, with a high resolution(small misorientation step). We also show a good agreement of local photoluminescence emission wavelength with simulation of transition energy based on synchrotron radiation microbeam X-ray diffraction(SR-XRD) data and estimated Stokes shift. We observe that the substrate misorientation influences also the In Ga N waveguide and Al Ga N cladding composition. Still, we showed through simulation of the optical confinement factor of a full laser diode structure that good light guiding properties should be preserved in the whole misorientation range studied here. This proves the usefulness of misorientation modification in applications like broadband superluminescent diodes or multicolor laser arrays.
