Laser beam welding of aluminum alloys is expected to offer good mechanical properties of welded joints. In this experimental work reported, CO2 laser beam autogenoas welding and wire feed welding are conducted on 4 mm...Laser beam welding of aluminum alloys is expected to offer good mechanical properties of welded joints. In this experimental work reported, CO2 laser beam autogenoas welding and wire feed welding are conducted on 4 mm thick 5083- H321 aluminum alloy sheets at different welding variables. The mechanical properties and microstructure characteristics of the welds are evaluated through tensile tests, micro-hardness tests, optical microscopy and scanning electron microscopy （SEM）. Experimental results indicate that both the tensile strength and hardness of laser beam welds are affected by the constitution of filler material, except the yield strength. The soften region of laser beam welds is not in the heat-affected zone （ HAZ ）. The tensile fracture of laser beam welded specimens takes place in the weld zone and close to the weld boundary because of different filler materials. Some pores are found on the fracture face, including hydrogen porosities and blow holes, but these pores have no influence on the tensile strength of laser beam welds. Tensile strength values of laser beam welds with filler wire are up to 345.57 MPa, 93% of base material values, and yield strengths of laser beam welds are equivalent to those of base metal （264. 50 MPa）.展开更多
This paper reports that La-doped BiFeO3 （Bil-xLaxFeO3, x = 0, 0.1, 0.2, 0.3, 0.6, 0.8 and 1.0） were studied by using micro-Raman spectroscopy and x-ray diffraction （XRD）. The XRD patterns indicate that the structu...This paper reports that La-doped BiFeO3 （Bil-xLaxFeO3, x = 0, 0.1, 0.2, 0.3, 0.6, 0.8 and 1.0） were studied by using micro-Raman spectroscopy and x-ray diffraction （XRD）. The XRD patterns indicate that the structure of Bi1-xLaxFeO3 changes from rhombohedral BiFeO3 to orthorhombic LaFeO3. The results of Raman spectroscopy show good agreement with the XRD results. Strikingly, the phonon peak at around 610 cm^-1 and the two-phonon peaks in the high frequency range exist in all compounds and enhance with increasing La substitution. The increasing intensity of the 610 cm-1 peak is attributed to the changes in the FeO6 octahedron during the rhombohedral-orthorhombic phase transition. The enhancements of the two-phonon peaks are associated with the breakdown of the cycloid spin configuration with the appearance of the orthorhombic structure. These results indicate the existence of strong spin phonon coupling in Bi1-xLaxFeO3, which may provide useful information for understanding the effects of La content on the structural and magnetic properties of Bi1 -xLaxFeO3.展开更多
We investigate a high-energy good-beam-quality krypton-lamp-pumped pulsed Nd： YA G solid-state laser with one pump cavity. The symmetrical resonator laser is developed and is rated at 80 J with beam parameter product...We investigate a high-energy good-beam-quality krypton-lamp-pumped pulsed Nd： YA G solid-state laser with one pump cavity. The symmetrical resonator laser is developed and is rated at 80 J with beam parameter product 12mm mrad. The total system electro-optics efficiency of the lamp-pumped YAG laser is as high as 3.3% and the stability of output energy is ±2% with pulse width tunable between 0.1 ms and 10ms. The experimental results are consistent with the theoretical analysis and simulation.展开更多
Ultrashort pulses were generated in passively mode-locked Nd：YAC and Nd：CdVO4 lasers pumped by a pulsed laser diode with 10-Hz repetition rate. Stable mode-locked pulse trains were produced with the pulse width of 1...Ultrashort pulses were generated in passively mode-locked Nd：YAC and Nd：CdVO4 lasers pumped by a pulsed laser diode with 10-Hz repetition rate. Stable mode-locked pulse trains were produced with the pulse width of 10 ps. The evolution of the mode-locked pulse was observed in the experiment and was discussed in detail. Comparing the pulse evolutions of Nd：YAG and Nd：GdVO4 lasers, we found that the buildup time of the steady-state mode-locking with semiconductor saturable absorber mirrors （SESAMs） was relevant to the upper-state lifetime and the emission cross-section of the gain medium.展开更多
Stable continuous-wave passive mode-locking of diode-end-pumped Nd:GdVO4 and Nd:YAG lasers with semiconductor saturable absorber mirrors (SESAMs) are reported. The comparative study shows that the Nd:GdVO4 crystal is ...Stable continuous-wave passive mode-locking of diode-end-pumped Nd:GdVO4 and Nd:YAG lasers with semiconductor saturable absorber mirrors (SESAMs) are reported. The comparative study shows that the Nd:GdVO4 crystal is efficient to decrease the Q-switched mode-locking tendency, and easier to continuous-wave (CW) mode lock than Nd:YAG.展开更多
CO2 laser is employed to join a piece of powder metallurgical material （PMM） to a stainless steel in butt joint welding mode. The powder Ni35, as a filler powder, is used. The weld metal comes from three parts of st...CO2 laser is employed to join a piece of powder metallurgical material （PMM） to a stainless steel in butt joint welding mode. The powder Ni35, as a filler powder, is used. The weld metal comes from three parts of stainless steel, powder Ni35, and Cu in W-Cu PMM. It is indicated that some parts of the W-Cu base metal are heated by laser and the metal Cu at the width of 0.06--0.12 mm from the edge is melted into the melting pool in the laser welding process. The formation of firm weld joint is just because that the melting liquid metal could fill the position occupied by metal Cu and surround the metal W granules fully. The analysis results indicate that the mechanism of the laser welding for stainless steel and W-Cu alloy is a special mode of fusion-brazing welding.展开更多
We present a compact and high output power diode end-pumped Nd:YAG laser which operates at the wavelength of 1123 nm. Continuous wave (CW) laser output of 2.6 W was achieved at the incident pump power of 15.9 W, indic...We present a compact and high output power diode end-pumped Nd:YAG laser which operates at the wavelength of 1123 nm. Continuous wave (CW) laser output of 2.6 W was achieved at the incident pump power of 15.9 W, indicating an overall optical-optical conversion efficiency of 16.4%, and the slope efficiency was 18%.展开更多
The robust phase locking of a linear diode array consisting of 49 broad-area emitters was demonstrated. The single lobe in the far field with output power of 0.83 W was observed. The far-field divergence was reduced t...The robust phase locking of a linear diode array consisting of 49 broad-area emitters was demonstrated. The single lobe in the far field with output power of 0.83 W was observed. The far-field divergence was reduced to 2.0 mrad. The spectral bandwidth was reduced from 1.7 to 0.13 nm.展开更多
A flash-lamp-pumped Nd：YAG regenerative amplifier has been developed at 1.06 μm, seeded with 10- ps pulses from a diode-end-pumped and mode-locked Nd：YAG oscillator with homemade semiconductor saturable absorber mi...A flash-lamp-pumped Nd：YAG regenerative amplifier has been developed at 1.06 μm, seeded with 10- ps pulses from a diode-end-pumped and mode-locked Nd：YAG oscillator with homemade semiconductor saturable absorber mirror （SESAM）. The pulse energy was amplified to 2 mJ by the regenerative amplifier at 10-Hz repetition rate. In two-stages amplifier the regenerative amplified pulse energy was amplified to 100 m J, and 35-mJ double frequency at 532 nm was obtained by extra-cavity double frequency with a KTP crystal.展开更多
基金This research was supported by Major Subject Foundation of Beijing University of Technology
文摘Laser beam welding of aluminum alloys is expected to offer good mechanical properties of welded joints. In this experimental work reported, CO2 laser beam autogenoas welding and wire feed welding are conducted on 4 mm thick 5083- H321 aluminum alloy sheets at different welding variables. The mechanical properties and microstructure characteristics of the welds are evaluated through tensile tests, micro-hardness tests, optical microscopy and scanning electron microscopy （SEM）. Experimental results indicate that both the tensile strength and hardness of laser beam welds are affected by the constitution of filler material, except the yield strength. The soften region of laser beam welds is not in the heat-affected zone （ HAZ ）. The tensile fracture of laser beam welded specimens takes place in the weld zone and close to the weld boundary because of different filler materials. Some pores are found on the fracture face, including hydrogen porosities and blow holes, but these pores have no influence on the tensile strength of laser beam welds. Tensile strength values of laser beam welds with filler wire are up to 345.57 MPa, 93% of base material values, and yield strengths of laser beam welds are equivalent to those of base metal （264. 50 MPa）.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10674171 and 10874236)
文摘This paper reports that La-doped BiFeO3 （Bil-xLaxFeO3, x = 0, 0.1, 0.2, 0.3, 0.6, 0.8 and 1.0） were studied by using micro-Raman spectroscopy and x-ray diffraction （XRD）. The XRD patterns indicate that the structure of Bi1-xLaxFeO3 changes from rhombohedral BiFeO3 to orthorhombic LaFeO3. The results of Raman spectroscopy show good agreement with the XRD results. Strikingly, the phonon peak at around 610 cm^-1 and the two-phonon peaks in the high frequency range exist in all compounds and enhance with increasing La substitution. The increasing intensity of the 610 cm-1 peak is attributed to the changes in the FeO6 octahedron during the rhombohedral-orthorhombic phase transition. The enhancements of the two-phonon peaks are associated with the breakdown of the cycloid spin configuration with the appearance of the orthorhombic structure. These results indicate the existence of strong spin phonon coupling in Bi1-xLaxFeO3, which may provide useful information for understanding the effects of La content on the structural and magnetic properties of Bi1 -xLaxFeO3.
基金Supported by the National Natural Science Foundation of China under Grant No 604070090, and the Beijing Key Project for Technology under Grant No 954810900.
文摘We investigate a high-energy good-beam-quality krypton-lamp-pumped pulsed Nd： YA G solid-state laser with one pump cavity. The symmetrical resonator laser is developed and is rated at 80 J with beam parameter product 12mm mrad. The total system electro-optics efficiency of the lamp-pumped YAG laser is as high as 3.3% and the stability of output energy is ±2% with pulse width tunable between 0.1 ms and 10ms. The experimental results are consistent with the theoretical analysis and simulation.
基金This work was supported by the National Nature Science Foundation of Beijing under Grant No. 3021001 and the foundation of Liaocheng University.
文摘Ultrashort pulses were generated in passively mode-locked Nd：YAC and Nd：CdVO4 lasers pumped by a pulsed laser diode with 10-Hz repetition rate. Stable mode-locked pulse trains were produced with the pulse width of 10 ps. The evolution of the mode-locked pulse was observed in the experiment and was discussed in detail. Comparing the pulse evolutions of Nd：YAG and Nd：GdVO4 lasers, we found that the buildup time of the steady-state mode-locking with semiconductor saturable absorber mirrors （SESAMs） was relevant to the upper-state lifetime and the emission cross-section of the gain medium.
基金This work was supported by the National Natural Sci-ence Foundation of China under Grant No.3021001.
文摘Stable continuous-wave passive mode-locking of diode-end-pumped Nd:GdVO4 and Nd:YAG lasers with semiconductor saturable absorber mirrors (SESAMs) are reported. The comparative study shows that the Nd:GdVO4 crystal is efficient to decrease the Q-switched mode-locking tendency, and easier to continuous-wave (CW) mode lock than Nd:YAG.
基金This work was supported by the Nature Science Fund of Beijing.
文摘CO2 laser is employed to join a piece of powder metallurgical material （PMM） to a stainless steel in butt joint welding mode. The powder Ni35, as a filler powder, is used. The weld metal comes from three parts of stainless steel, powder Ni35, and Cu in W-Cu PMM. It is indicated that some parts of the W-Cu base metal are heated by laser and the metal Cu at the width of 0.06--0.12 mm from the edge is melted into the melting pool in the laser welding process. The formation of firm weld joint is just because that the melting liquid metal could fill the position occupied by metal Cu and surround the metal W granules fully. The analysis results indicate that the mechanism of the laser welding for stainless steel and W-Cu alloy is a special mode of fusion-brazing welding.
文摘We present a compact and high output power diode end-pumped Nd:YAG laser which operates at the wavelength of 1123 nm. Continuous wave (CW) laser output of 2.6 W was achieved at the incident pump power of 15.9 W, indicating an overall optical-optical conversion efficiency of 16.4%, and the slope efficiency was 18%.
基金This work was supported by the National Natural Science Foundation of China (No. 10276003) the Nat ural Science Foundation of Beijing (No. 4051001).
文摘The robust phase locking of a linear diode array consisting of 49 broad-area emitters was demonstrated. The single lobe in the far field with output power of 0.83 W was observed. The far-field divergence was reduced to 2.0 mrad. The spectral bandwidth was reduced from 1.7 to 0.13 nm.
基金This work was supported by Ministry of Science and Technology of China (No. JG-2000-05) the Natural Science Foundation of Beijing (No. 3021001)the foundation of Liaochens University.
文摘A flash-lamp-pumped Nd：YAG regenerative amplifier has been developed at 1.06 μm, seeded with 10- ps pulses from a diode-end-pumped and mode-locked Nd：YAG oscillator with homemade semiconductor saturable absorber mirror （SESAM）. The pulse energy was amplified to 2 mJ by the regenerative amplifier at 10-Hz repetition rate. In two-stages amplifier the regenerative amplified pulse energy was amplified to 100 m J, and 35-mJ double frequency at 532 nm was obtained by extra-cavity double frequency with a KTP crystal.
