Browsing by Author "Hwang, RY"

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Corrosion behaviour of weld heat affected zone of aluminium alloy 7075
(1997)
Hwang, RY
;
Chou, CP
;
機械工程學系
;
Department of Mechanical Engineering
The microstructure of the weld heat affected zone (HAZ) of alloy 7075 was simulated using a Gleeble system. The corrosion behaviour of several locations in the weld HAZ was investigated by means of differential scanning calorimetry, electrochemical measurement in 3.5 wt-%NaCl solution, and exfoliation corrosion tests. Different exfoliation corrosion morphologies for the base metal and weld HAZ were also observed. The corrosion morphology of the weld HAZ was mainly related to the degree of precipitation of eta' phase in the matrix. The HAZ in the region of the peak temperature 377 degrees C contained the most precipitation of eta phase, but no effect on corrosion morphology as a result of T6 post-weld heat treatment was observed. (C) 1997 The Institute of Materials.
Hot ductility behaviour of Al-Li alloy AA2091-T3
(1997)
Hwang, RY
;
Chou, CP
;
機械工程學系
;
Department of Mechanical Engineering
The hot ductility behaviour of the AE-Li alloy 2091-T3 was investigated using hot ductility testing of the simulated heat affected zone (HAZ) using a Gleeble 1500 machine. Alloy 2091 displayed lower ductility, greater susceptibility to HAZ cracking, and poor ductility recovery on cooling from the nil strength temperature, compared with alloy 2219. Optical metallography and electron microscopy revealed that the ductility loss was accompanied by fracture transition front ductile transgranular mode to brittle intel granular mode. It was found that the HAZ intergranular liquation cracking was caused by non-equilibrium eutectic melting of T-2 phase precipitated at grain boundaries. (C) 1997 The Institute of Materials.
Microstructure and corrosion properties of AA2091-T3 in weld heat affected zone
(1999)
Chen, MH
;
Hwang, RY
;
Chou, CP
;
機械工程學系
;
Department of Mechanical Engineering
The microstructure and corrosion behaviour of at? AA2091-T3 alloy weld hear affected zone (HAZ) were investigated using differential scanning calorimetry and electrochemical measurements iii 3.5%NaCl solution. The delta' phase was precipitated during the welding cooling process. The ai amount of delta' precipitates depends on the peak temperature of the,veld thermal cycle. The quantity of Guinier-Preston (GP) zones,vas related to the duration of natural aging. Variation of pitting potential of the weld HAZ was due to the lithium content in the matrix. The increasing dissolution Of GP zones and delta' phase was accompanied by increasing lithium contents in the matrix and caused a negative shifting of pitting potential. The legion containing the lowest quantity of GP zones and delta' phase had the lowest pitting potential. The higher the peak temperature of rite weld thermal cycles the mole precipitation of T-2 phase on gl ain boundaries occurs. These T-2 phases can cause severe intergranular exfoliation corrosion.
The study on microstructural and mechanical properties of weld heat affected zone of 7075-T651 aluminum alloy
(1997-12-22)
Hwang, RY
;
Chou, CP
;
機械工程學系
;
Department of Mechanical Engineering