Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardnes...Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardness profiles, microstructural features and residual stress distribution of aluminium alloy joints were reported. The use of pulsed current technique is found to improve the tensile properties of the weld compared with continuous current welding due to grain refinement occurring in the fusion zone.展开更多
Empirical relationship was developed to predict the fatigue life of gas metal arc welded （GMAW） cruciform joints failing from root region. High strength, age hardenable aluminium alloy of AA7075-T6 grade was used as...Empirical relationship was developed to predict the fatigue life of gas metal arc welded （GMAW） cruciform joints failing from root region. High strength, age hardenable aluminium alloy of AA7075-T6 grade was used as the base material. The design of experiments concept was used to optimize the required number of fatigue testing experiments. Fatigue experiment was conducted in a servo hydraulic controlled fatigue testing machine under constant amplitude loading. The empirical relationship was developed. By using the developed empirical relationship, the fatigue life of GMAW cruciform joints failing from root region was predicted at 95% confidence level. The effect of cruciform joint dimensions on fatigue life was discussed in detail.展开更多
Double-V butt TIG welding process was performed on two plates of AA6061-T6 using ER5356 filler. The microstructure,mechanical and nanomechanical properties of the joint were evaluated in as-welded and after post weld ...Double-V butt TIG welding process was performed on two plates of AA6061-T6 using ER5356 filler. The microstructure,mechanical and nanomechanical properties of the joint were evaluated in as-welded and after post weld heat treatment (PWHT) usingXRD, FESEM, EBSD, nanoindentation and tensile tests. The results show that PWHT led to microstructural recovery of the heataffected zone (HAZ) in addition to the appearance of β-phase (Al3Mg2) at the grain boundaries of weld zone. The hardness (Hnano) inall zones increased after PWHT while the elastic modulus (Enano) was improved from 69.93 GPa to 81 GPa in weld area. All resultsindicate that PWHT has created a homogenous microstructure in the weld zone in addition to outstanding improvement inmechanical properties for the weld zone which surpass the base metal.展开更多
AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding （GTAW）, electron beam welding （EBW） and friction stir welding （FSW） processes. The effects o...AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding （GTAW）, electron beam welding （EBW） and friction stir welding （FSW） processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.展开更多
The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding （TIG） and metal inert gas weldi...The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding （TIG） and metal inert gas welding （MIG） processes. The effect of welding processes was analysed based on optical microscopy image, tensile testing, and Vickers micro-hardness measurements. The results showed that the tensile strengths of the TIG-welded joints were better than those of the MIG-welded joints, due to the contribution of fine equiaxed grains formation with narrower spacing arms. In terms of joint efficiency, the TIG process produced more reliable strength, which was about 25% higher compared to the MIG-joint. A significant decay of hardness was recorded in the adjacent of the weld bead zone, shown in both joints, related to phase transformation, induced by high temperatures experienced by material. A very low hardness, which was about 1.08 GPa, was recorded in the MIG-weldcd specimens. The extent of the heat-affected-zone （HAZ） in the MIG-welded joints was slightly wider than those of the TIG-welded specimens, which corresponded with a higher heat input per unit length.展开更多
Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas(TIG)welded joint were analyzed in detail.In weld zone(WZ),α+θeutectic structure f...Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas(TIG)welded joint were analyzed in detail.In weld zone(WZ),α+θeutectic structure formed at grain boundaries with no precipitates inside the grains.In partially melted zone(PMZ),symbiotic eutectic or divorced eutectic formed at grain boundaries and needle-likeθ′phases appeared in the secondary heated zone.In over aged zone(OAZ),the coarsening and dissolution ofθ′phases occurred and mostθ′phases transformed intoθphases.In general heat affected zone(HAZ),θ′phases coarsened.Factors such as the strengthening phases,the grain size,the Cu content in matrix and the dislocation density can affect the mechanical properties in different regions of the joint.Moreover,a model describing the relationship between mechanical properties of the material and the volume fraction of precipitates,the average diameter of precipitates and the concentration of soluble elements was proposed.展开更多
The plasma-MIG welding torch was developed.5A06 aluminum alloys with V-grooves were welded in a single pass in the plasma-MIG welding process and the joints were examined by X-ray diffractometry analysis and mechanica...The plasma-MIG welding torch was developed.5A06 aluminum alloys with V-grooves were welded in a single pass in the plasma-MIG welding process and the joints were examined by X-ray diffractometry analysis and mechanical tests.The orthogonal experimental design was used to study the influence of plasma-MIG welding parameters on the aluminum weld porosity.The mixed orthogonal matrix L16(4 4×2 3) and analysis of variance (ANOVA)technique were employed to optimize the welding parameters.The experimental results indicate that the effect of plasma gas flow rate is dominant,the secondary factors are MIG welding voltage,welding speed,wire feed rate and plasma current in turn.Confirmation experiments were conducted under optimum conditions and there was almost no porosity in the welded joints,thus good mechanical performance joints were obtained.展开更多
An experimental and computational fluid dynamics (CFD) numerical study of the sintering of an Al?7Zn?2.5Mg?1Cu alloy in flowing nitrogen was presented. Three rectangular bars with dimensions of 56 mm × 10 mm ...An experimental and computational fluid dynamics (CFD) numerical study of the sintering of an Al?7Zn?2.5Mg?1Cu alloy in flowing nitrogen was presented. Three rectangular bars with dimensions of 56 mm × 10 mm × 4.5 mm each, equally spaced 2 or 10 mm apart, were sintered in one batch at 620 °C for 40 min in a tube furnace. The pore distribution in the selected cross section of sintered samples was found to be dependent on the sample separation distance and the distance from the cross section examined to the sample end. A three-dimensional (3D) CFD model was developed to investigate the nitrogen gas behavior near each sintering surface of the three samples during isothermal sintering. The variation in porosity in the cross section of each sintered sample along sample length was found to be closely related to the nitrogen gas flow field near the sintering surfaces.展开更多
文摘Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardness profiles, microstructural features and residual stress distribution of aluminium alloy joints were reported. The use of pulsed current technique is found to improve the tensile properties of the weld compared with continuous current welding due to grain refinement occurring in the fusion zone.
文摘Empirical relationship was developed to predict the fatigue life of gas metal arc welded （GMAW） cruciform joints failing from root region. High strength, age hardenable aluminium alloy of AA7075-T6 grade was used as the base material. The design of experiments concept was used to optimize the required number of fatigue testing experiments. Fatigue experiment was conducted in a servo hydraulic controlled fatigue testing machine under constant amplitude loading. The empirical relationship was developed. By using the developed empirical relationship, the fatigue life of GMAW cruciform joints failing from root region was predicted at 95% confidence level. The effect of cruciform joint dimensions on fatigue life was discussed in detail.
基金the financial support for this study from the Malaysian Ministry of Higher Education(MOHE) through the Fundamental Research Grant Scheme and Exploratory Research Grant Scheme
文摘Double-V butt TIG welding process was performed on two plates of AA6061-T6 using ER5356 filler. The microstructure,mechanical and nanomechanical properties of the joint were evaluated in as-welded and after post weld heat treatment (PWHT) usingXRD, FESEM, EBSD, nanoindentation and tensile tests. The results show that PWHT led to microstructural recovery of the heataffected zone (HAZ) in addition to the appearance of β-phase (Al3Mg2) at the grain boundaries of weld zone. The hardness (Hnano) inall zones increased after PWHT while the elastic modulus (Enano) was improved from 69.93 GPa to 81 GPa in weld area. All resultsindicate that PWHT has created a homogenous microstructure in the weld zone in addition to outstanding improvement inmechanical properties for the weld zone which surpass the base metal.
基金Project DRAO/08/1061356/M1 supported by Aeronautical Research & Development Board (ARDB),New Delhi,India
文摘AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding （GTAW）, electron beam welding （EBW） and friction stir welding （FSW） processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.
基金University Science Malaysia (USM) and Malaysia Ministry of Education (MoE) for their technical and financial support
文摘The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding （TIG） and metal inert gas welding （MIG） processes. The effect of welding processes was analysed based on optical microscopy image, tensile testing, and Vickers micro-hardness measurements. The results showed that the tensile strengths of the TIG-welded joints were better than those of the MIG-welded joints, due to the contribution of fine equiaxed grains formation with narrower spacing arms. In terms of joint efficiency, the TIG process produced more reliable strength, which was about 25% higher compared to the MIG-joint. A significant decay of hardness was recorded in the adjacent of the weld bead zone, shown in both joints, related to phase transformation, induced by high temperatures experienced by material. A very low hardness, which was about 1.08 GPa, was recorded in the MIG-weldcd specimens. The extent of the heat-affected-zone （HAZ） in the MIG-welded joints was slightly wider than those of the TIG-welded specimens, which corresponded with a higher heat input per unit length.
基金Project(U1637601)supported by the Joint Funds of the National Natural Science Foundation of China。
文摘Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas(TIG)welded joint were analyzed in detail.In weld zone(WZ),α+θeutectic structure formed at grain boundaries with no precipitates inside the grains.In partially melted zone(PMZ),symbiotic eutectic or divorced eutectic formed at grain boundaries and needle-likeθ′phases appeared in the secondary heated zone.In over aged zone(OAZ),the coarsening and dissolution ofθ′phases occurred and mostθ′phases transformed intoθphases.In general heat affected zone(HAZ),θ′phases coarsened.Factors such as the strengthening phases,the grain size,the Cu content in matrix and the dislocation density can affect the mechanical properties in different regions of the joint.Moreover,a model describing the relationship between mechanical properties of the material and the volume fraction of precipitates,the average diameter of precipitates and the concentration of soluble elements was proposed.
文摘The plasma-MIG welding torch was developed.5A06 aluminum alloys with V-grooves were welded in a single pass in the plasma-MIG welding process and the joints were examined by X-ray diffractometry analysis and mechanical tests.The orthogonal experimental design was used to study the influence of plasma-MIG welding parameters on the aluminum weld porosity.The mixed orthogonal matrix L16(4 4×2 3) and analysis of variance (ANOVA)technique were employed to optimize the welding parameters.The experimental results indicate that the effect of plasma gas flow rate is dominant,the secondary factors are MIG welding voltage,welding speed,wire feed rate and plasma current in turn.Confirmation experiments were conducted under optimum conditions and there was almost no porosity in the welded joints,thus good mechanical performance joints were obtained.
基金supported by Ampal Inc., a member of the United States Metal Powders Group, through the CAST CRC, a Cooperative Research Centre established by the Australian Commonwealth Government
文摘An experimental and computational fluid dynamics (CFD) numerical study of the sintering of an Al?7Zn?2.5Mg?1Cu alloy in flowing nitrogen was presented. Three rectangular bars with dimensions of 56 mm × 10 mm × 4.5 mm each, equally spaced 2 or 10 mm apart, were sintered in one batch at 620 °C for 40 min in a tube furnace. The pore distribution in the selected cross section of sintered samples was found to be dependent on the sample separation distance and the distance from the cross section examined to the sample end. A three-dimensional (3D) CFD model was developed to investigate the nitrogen gas behavior near each sintering surface of the three samples during isothermal sintering. The variation in porosity in the cross section of each sintered sample along sample length was found to be closely related to the nitrogen gas flow field near the sintering surfaces.
