The effect of small tool pin profiles on the microstructures and mechanical properties of 6061 aluminum alloy joints using friction stir welding （FSW） technique was investigated. Three different tool pin profiles： ...The effect of small tool pin profiles on the microstructures and mechanical properties of 6061 aluminum alloy joints using friction stir welding （FSW） technique was investigated. Three different tool pin profiles： threaded tapered cylindrical （T1）, triangular （T2） and square （T3） were used to produce the joints. The results indicate that the weld joints are notably affected by joining with different tool pin profiles. The triangular tool pin profile produces thebest metallurgicaland mechanical weld properties compared with other tool pin profiles. Besides, the lowest tensile strength and microhardness are obtained for the joint friction stir welded with square tool pin profile. It is observed that the smaller tool pin profile and shoulder diameter lead to narrow region of heat affected zone （HAZ） and a desired level of softening. The fracture surface examination shows that the joints are also affected when welding with different types of tool pin profiles. The fracture surface shows that the triangular specimen fails with a ductile fracture mode during the tensile test, while the brittle fracture modes are observed in the joints fabricated with other tool pin profiles （T1 and T3）.展开更多
Ca3Co4O9 is a p-type semiconducting material that is well-known for its thermoelectric(TE),magnetic,electronic,and electro-optic properties.In this study,sol–gel autoignition was used to prepare Ca3Co4O9 at different...Ca3Co4O9 is a p-type semiconducting material that is well-known for its thermoelectric(TE),magnetic,electronic,and electro-optic properties.In this study,sol–gel autoignition was used to prepare Ca3Co4O9 at different calcination temperatures(773,873,973,and 1073 K)and time(4,6,8,10,12,and 14 h)using starch as a fuel.The phase and microstructure of the prepared Ca3Co4O9 powder were investigated.Thermogravimetry–differential thermal analysis(TGA)confirms that the final weight loss occurred at 1073 K to form Ca3Co4O9 stable powder.The variable-pressure scanning electron microscopy(VP-SEM)images show that the size of powder particles increases from 1.15 to 1.47μm as calcination time increases from 4 to 12 h,and the size remains almost constant thereafter.A similar pattern is also observed on the increment of the crystallite size and percentage of crystallinity with X-ray diffraction(XRD)analysis.The highest crystallinity is found about 92.9%when the powder was calcinated at 1073 K for 12 and 14 h with 458 and 460Åcrystallite size,respectively.Energy dispersive X-ray spectroscopy(EDS)analysis demonstrates that the calcinated powder has a high intensity of Ca,Co,and O with uniform distribution.High-resolution transmission electron microscopy(HRTEM)images prove that there is no distinct lattice distortion defect on the crystal structure.展开更多
基金supported by the grant No.900100338 of the Universiti Malaysia Perlis (Uni MAP)the outstanding support provided by the staff in the School of Materials Engineering in Uni MAP+1 种基金the Centre for Low Carbon Transport and Institute for Vehicle System Engineering in Universiti Teknologi Malaysia (UTM)the School of Materials Engineering and Mineral Resources in Universiti Sains Malaysia (USM)
文摘The effect of small tool pin profiles on the microstructures and mechanical properties of 6061 aluminum alloy joints using friction stir welding （FSW） technique was investigated. Three different tool pin profiles： threaded tapered cylindrical （T1）, triangular （T2） and square （T3） were used to produce the joints. The results indicate that the weld joints are notably affected by joining with different tool pin profiles. The triangular tool pin profile produces thebest metallurgicaland mechanical weld properties compared with other tool pin profiles. Besides, the lowest tensile strength and microhardness are obtained for the joint friction stir welded with square tool pin profile. It is observed that the smaller tool pin profile and shoulder diameter lead to narrow region of heat affected zone （HAZ） and a desired level of softening. The fracture surface examination shows that the joints are also affected when welding with different types of tool pin profiles. The fracture surface shows that the triangular specimen fails with a ductile fracture mode during the tensile test, while the brittle fracture modes are observed in the joints fabricated with other tool pin profiles （T1 and T3）.
基金This research study was supported by the Ministry of Education Malaysia(MOE)for the FRGS Grant(R.J130000.7824.4F723)Universiti Teknologi Malaysia(UTM)research grant(Q.J130000.2524.17H83).
文摘Ca3Co4O9 is a p-type semiconducting material that is well-known for its thermoelectric(TE),magnetic,electronic,and electro-optic properties.In this study,sol–gel autoignition was used to prepare Ca3Co4O9 at different calcination temperatures(773,873,973,and 1073 K)and time(4,6,8,10,12,and 14 h)using starch as a fuel.The phase and microstructure of the prepared Ca3Co4O9 powder were investigated.Thermogravimetry–differential thermal analysis(TGA)confirms that the final weight loss occurred at 1073 K to form Ca3Co4O9 stable powder.The variable-pressure scanning electron microscopy(VP-SEM)images show that the size of powder particles increases from 1.15 to 1.47μm as calcination time increases from 4 to 12 h,and the size remains almost constant thereafter.A similar pattern is also observed on the increment of the crystallite size and percentage of crystallinity with X-ray diffraction(XRD)analysis.The highest crystallinity is found about 92.9%when the powder was calcinated at 1073 K for 12 and 14 h with 458 and 460Åcrystallite size,respectively.Energy dispersive X-ray spectroscopy(EDS)analysis demonstrates that the calcinated powder has a high intensity of Ca,Co,and O with uniform distribution.High-resolution transmission electron microscopy(HRTEM)images prove that there is no distinct lattice distortion defect on the crystal structure.
