Hidetoshi FUJII
,
Yosuke SUMI
,
Manabu TANAKA
,
Kiyoshi NOGI
材料科学技术（英）
Gas tungsten arc (GTA) welding was performed both in a microgravity environment and in a terrestrial environment, and the arc shapes in both environments were compared. A microgravity condition was obtained using the free fall system at the Japan Microgravity Center. The system can maintain a 10 s microgravity of less than 10-5 g. A water-cooled Cu plate was used to simplify the arc phenomenon. The electric arc current was between 15 and 80 A, and the shielding and atmospheric gas was 99.9995% Ar and its flowing rate was 10 l/min. The polarity was a direct current electrode negative (DCEN). The arc gap was 3 mm and careful attention was also paid to the arc gap in both the terrestrial and microgravity environments being the same. As a result, it was found that no effect of gravity on the arc shape is observed under general welding conditions (over 60 A). When the electric arc current is lower than 25 A, the arc shape is determined by the initial position of the arc root and is constant with time. Accordingly, it can not be judged whether or not the arc shape is affected by gravity for this range. When the electric arc current is between 25 A and 60 A, it is estimated that the arc shape is not affected by gravity though it is occasionally affected by other minor effects.
关键词:
Microgravity
,
null
,
null
,
null
Huijie LIU
,
Hidetoshi FUJII
,
Masakatsu MAEDA
,
Kiyoshi NOGI
材料科学技术（英）
The tensile fracture location characterizations of the friction stir welded joints of the AA1050-H24 and AA6061-T6 Al alloys were evaluated in this study. The experimental results show that the fracture locations of the joints are different for the different Al alloys, and they are affected by the FSW parameters. When the joints are free of welding defects, the AA1050-H24 joints are fractured in the HAZ and TMAZ on the AS and the fracture parts undergo a large amount of plastic deformation, while the AA6061-T6 joints are fractured in the HAZ on the RS and the fracture surfaces are inclined a certain degree to the bottom surfaces of the joints. When some welding defects exist in the joints, the AA1050-H24 joints are fractured on the RS or AS, the AA6061-T6 joints are fractured on the RS, and all the fracture locations are near to the weld center. The fracture locations of the joints are dependent on the internal structures of the joints and can be explained by the microhardness profiles and defect morphologies of the joints.
关键词:
Friction stir welding
,
null
,
null
Feng XIAO
,
Liang FANG
,
Kiyoshi NOGI
材料科学技术（英）
Surface tension of molten Ni and Ni-Co (5 and 10 mass fraction) alloys was measured at the temperature range of 1773~1873 K using an improved sessile drop method with an alumina substrate in an Ar+3%H2 atmosphere. The error of the data obtained was analyzed. The surface tension of molten Ni and Ni-Co (5 and 10 mass fraction) alloys decreases with increasing temperature. The influence of Co on the surface tension of Ni-Co alloys is little in the studied Co concentration range.
关键词:
Nickel
,
null
,
null
,
null
