Papers by Author: Shui Li Gong

Abstract: Electron beam surfi-sculpt is a new metal surface processing technology, which is potentially used in many areas. In this paper, forming mechaniam of electron beam surfi-sculpt has been investigated by experiments and numerical simulation. Electron beam surfi-sculpt of Ti-6Al-4V was realized by a new control system and a innovative hexagon scanning waveform. At the same time, microstructure of protrusions was analysed. All the results of experiments and simulation show that forming mechanism is the interaction of vapour pressure and surface tension, but surface tension plays a dominant role during electron beam surfi-sculpt process.

Abstract: The distribution and appearance characteristics of porosities in laser penetrated weld of aluminum alloy were observed, and the formation mechanisms of porosities were analyzed in detail, and the influences of twin spot laser energy distribution on porosities were investigated. It showed that there are two kinds of porosities, metallurgical and technologic porosities, in laser penetrated weld of aluminum alloy. The formation of metallurgical porosities is related to the separation, congregation and incorporation of hydrogen in the weld pool, while instantaneous instability of the keyhole is an essential reason for the occurrence of technologic porosities. Twin spot laser energy distribution can enlarge diameters of the opening and the root of the keyhole, improve fluctuating conditions of the wall of the keyhole, increase stability of the keyhole, and consequently decrease technologic porosities in number, but it has no obvious influence on metallurgical porosities.

Abstract: In this paper, the keyhole of YAG laser welding 5A90 Al-Li alloy was observed and measured through the high speed camera. The characteristics of the keyhole and the effects of welding parameters were studied. The characteristics of the absorption of laser energy and the susceptivity for heat input in welding 5A90 were given. The results show that in this welding condition, the keyhole of laser welding 5A90 is nearly a taper and the highest temperature area is in the bottom. There are clear effects of heat input on the characteristics, especially the surface radius of keyhole and plasma/vapor in keyhole. Another phenomena is observed that sometime plasma/vapor could disappear in 0.3ms welding time, and this feature will be more remarkable as decrease of heat input. It shows that the absorption of energy is unsteady. It is known that when this instability reaches a certain value, an unsteady weld will be formed.

Abstract: The laser welding of Aluminum-Lithium alloy (Al-Li) alloy were conducted to investigate the weld porosity features in this paper. The results show that there are two kinds of weld porosity existing for laser welding Aluminum-Lithium alloy sheet. They are can be divided into metallurgical porosity and unstable keyhole porosity according to their different reason causing them. The mechanism of unstable keyhole porosity occurring was discussed according to the results of YAG laser welding processing. The methods how to reduce weld porosity for laser welding of Aluminum-Lithium alloy was also described.