Joining of dissimilar aluminium-copper is an emerging area of interest for both research and industry due to its complex nature.Friction stir welding was attempted to evaluate the joint strength without offset at the ...Joining of dissimilar aluminium-copper is an emerging area of interest for both research and industry due to its complex nature.Friction stir welding was attempted to evaluate the joint strength without offset at the butt line between AA6063 to HCP copper sheet under different combination of rotational speed of 800 and 1000 r/min and travel speed of 20 and 40 mm/min.Material flow was studied in detail for different combinations of parameters with optical microscopy and elemental mapping by energy dispersive X-ray spectroscopy（EDS）.The results were correlated with the microstructural characteristics and formation of intermetallics at the bond interface using microhardness test and X-ray diffraction（XRD） technique.Material flow clearly suggests that energy input at 800 r/min and 20 mm/min is sufficient to plasticize both the materials with formation of higher amount of thermodynamically stable and hard intermetallic phases Al4Cu9 and Al Cu4（slower cooling rate of 88 K/s） than that at 800 r/min and 40 mm/min（faster cooling rate of 154 K/s）,attributed maximum joint strength（~78.6% of aluminium base metal）.展开更多
Coated Electrodes with small amounts of nickel were developed for welding ductile iron(DI) and conversion of the same into austempered ductile iron(ADI) after austempering. Among six electrodes, Trials 3 and 4 were se...Coated Electrodes with small amounts of nickel were developed for welding ductile iron(DI) and conversion of the same into austempered ductile iron(ADI) after austempering. Among six electrodes, Trials 3 and 4 were selected for establishing crack-free weld deposits via preheating and post-weld heat treatment. Austenitization was performed at 900°C for 2 h and austempering at 300 or 350°C for three different holding times to observe the results of austempering with respect to the microstructure, hardness, and austempering kinetics of the samples. The microstructures of the weld deposits showed needle-like bainitic ferrite with small amounts of retained austenite when treated at 300°C and feathery bainitic ferrite with large amounts of retainedaustenite when treated at 350°C. The electrode labeled with Trial 3 revealed greater austenite contents than that labeled with Trial 4 when treated with a 2 h holding time regardless of the austempering temperature applied. The transformation rate of the bainitic ferrite of Trial 3 was relatively higher than that of Trial 4 and showed a lower rate constant, leading to a higher diffusion rate of carbon in austenite.展开更多
Friction stir welding （FSW） of 6061 aluminium alloy butt joint was carried out at each rotation speed of 600, 800, 1000, 1200 r/min for two different travel speeds, 80 and 100 mm/min, at a constant probe depth of 1....Friction stir welding （FSW） of 6061 aluminium alloy butt joint was carried out at each rotation speed of 600, 800, 1000, 1200 r/min for two different travel speeds, 80 and 100 mm/min, at a constant probe depth of 1.85 mm. The calculated energy input based on the FSW parameters studied shows that the ultimate tensile strength （UTS） of the butt joint is obtained within a certain range of energy input of 297 kJ to 354 kJ out of total range of energy input studied from 196 kJ to 405 kJ. The fatigue behaviors of high-strength and low-strength joints performed at different stress ratios, i.e., 0.5, 0.3, 0.1, -0.3, -0.5, indicate that the fatigue behaviors of both the welds are sensitive to the microstructural features, such as stir zone （SZ）, thermo mechanically affected zone （TMAZ） and heat affected zone （HAZ）. The observed fatigue strengths were discussed in terms of the microstructure, crack path behavior and fracture surface.展开更多
The effect of heat input on martensite formation and impact properties of gas metal arc welded modified ferritic stainless steel （409M） sheets （as received） with thickness of 4 mm was described in detail in this w...The effect of heat input on martensite formation and impact properties of gas metal arc welded modified ferritic stainless steel （409M） sheets （as received） with thickness of 4 mm was described in detail in this work. The welded joints were prepared under three heat input conditions, i.e. 0.4, 0.5 and 0.6 kJ/mm using two different austenitic filler wires （308L and 316L） and shielding gas composition of Ar ＋ 5% CO2. The welded joints were evaluated by microstructure and charpy impact toughness. The dependence of weld metal microstructure on heat input and filler wires were determined by dilution calculation, Creq/Nieq ratio, stacking fault energy （SFE）, optical microscopy （OM） and transmission electron microscopy （TEM）. It was observed that the microstructure as well as impact property of weld metal was significantly affected by the heat input and filler wire. Weld metals prepared by high heat input exhibited higher amount of martensite laths and toughness compared with those prepared by medium and low heat inputs, which was true for both the filler wires. Furthermore, 308L weld metals in general provided higher amount of martensite laths and toughness than 316L weld metals.展开更多
The effect of alloy segregation and delta （δ） ferrite contents on surface cracking of three standard （i.e. AISI 304L, AISI 310S and AISI 321） and two low nickel （i.e. LNi-1 and LNi-0.3） austenitic stainless ste...The effect of alloy segregation and delta （δ） ferrite contents on surface cracking of three standard （i.e. AISI 304L, AISI 310S and AISI 321） and two low nickel （i.e. LNi-1 and LNi-0.3） austenitic stainless steels （ASS） during hot roiling was investigated using optical microscopy （OM）, automatic image analyzer, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDX） and electron probe micro analyzer （EPMA）. It was observed that the amount of 6-ferrite varied among different grades and also distributed heterogeneously across the width of the steel plates. In general, low nickel ASS showed higher amount of 6-ferrite compared to the standard ASS grades. The tendency to surface cracking during hot rolling gradually increased with increasing 6-ferrite content. Interestingly, carbon and nitrogen exerted maximum effect on 6-ferrite formation. The higher carbon and nitrogen content in the steel decreased 6-ferMte content. In addition, the segregation of Cu and Mn plays significant role in low nickel ASS and Ni-Cr in case of standard ASS has profound effect on surface cracking of the steel plates. A possible cause of surface crack formation/origination in steel plates during hot rolling was discussed.展开更多
文摘Joining of dissimilar aluminium-copper is an emerging area of interest for both research and industry due to its complex nature.Friction stir welding was attempted to evaluate the joint strength without offset at the butt line between AA6063 to HCP copper sheet under different combination of rotational speed of 800 and 1000 r/min and travel speed of 20 and 40 mm/min.Material flow was studied in detail for different combinations of parameters with optical microscopy and elemental mapping by energy dispersive X-ray spectroscopy（EDS）.The results were correlated with the microstructural characteristics and formation of intermetallics at the bond interface using microhardness test and X-ray diffraction（XRD） technique.Material flow clearly suggests that energy input at 800 r/min and 20 mm/min is sufficient to plasticize both the materials with formation of higher amount of thermodynamically stable and hard intermetallic phases Al4Cu9 and Al Cu4（slower cooling rate of 88 K/s） than that at 800 r/min and 40 mm/min（faster cooling rate of 154 K/s）,attributed maximum joint strength（~78.6% of aluminium base metal）.
基金financially supported by the Department of Science and Technology(DST),New Delhi,India(No.SR/S3/ME/0037/2012)
文摘Coated Electrodes with small amounts of nickel were developed for welding ductile iron(DI) and conversion of the same into austempered ductile iron(ADI) after austempering. Among six electrodes, Trials 3 and 4 were selected for establishing crack-free weld deposits via preheating and post-weld heat treatment. Austenitization was performed at 900°C for 2 h and austempering at 300 or 350°C for three different holding times to observe the results of austempering with respect to the microstructure, hardness, and austempering kinetics of the samples. The microstructures of the weld deposits showed needle-like bainitic ferrite with small amounts of retained austenite when treated at 300°C and feathery bainitic ferrite with large amounts of retainedaustenite when treated at 350°C. The electrode labeled with Trial 3 revealed greater austenite contents than that labeled with Trial 4 when treated with a 2 h holding time regardless of the austempering temperature applied. The transformation rate of the bainitic ferrite of Trial 3 was relatively higher than that of Trial 4 and showed a lower rate constant, leading to a higher diffusion rate of carbon in austenite.
文摘Friction stir welding （FSW） of 6061 aluminium alloy butt joint was carried out at each rotation speed of 600, 800, 1000, 1200 r/min for two different travel speeds, 80 and 100 mm/min, at a constant probe depth of 1.85 mm. The calculated energy input based on the FSW parameters studied shows that the ultimate tensile strength （UTS） of the butt joint is obtained within a certain range of energy input of 297 kJ to 354 kJ out of total range of energy input studied from 196 kJ to 405 kJ. The fatigue behaviors of high-strength and low-strength joints performed at different stress ratios, i.e., 0.5, 0.3, 0.1, -0.3, -0.5, indicate that the fatigue behaviors of both the welds are sensitive to the microstructural features, such as stir zone （SZ）, thermo mechanically affected zone （TMAZ） and heat affected zone （HAZ）. The observed fatigue strengths were discussed in terms of the microstructure, crack path behavior and fracture surface.
文摘The effect of heat input on martensite formation and impact properties of gas metal arc welded modified ferritic stainless steel （409M） sheets （as received） with thickness of 4 mm was described in detail in this work. The welded joints were prepared under three heat input conditions, i.e. 0.4, 0.5 and 0.6 kJ/mm using two different austenitic filler wires （308L and 316L） and shielding gas composition of Ar ＋ 5% CO2. The welded joints were evaluated by microstructure and charpy impact toughness. The dependence of weld metal microstructure on heat input and filler wires were determined by dilution calculation, Creq/Nieq ratio, stacking fault energy （SFE）, optical microscopy （OM） and transmission electron microscopy （TEM）. It was observed that the microstructure as well as impact property of weld metal was significantly affected by the heat input and filler wire. Weld metals prepared by high heat input exhibited higher amount of martensite laths and toughness compared with those prepared by medium and low heat inputs, which was true for both the filler wires. Furthermore, 308L weld metals in general provided higher amount of martensite laths and toughness than 316L weld metals.
文摘The effect of alloy segregation and delta （δ） ferrite contents on surface cracking of three standard （i.e. AISI 304L, AISI 310S and AISI 321） and two low nickel （i.e. LNi-1 and LNi-0.3） austenitic stainless steels （ASS） during hot roiling was investigated using optical microscopy （OM）, automatic image analyzer, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDX） and electron probe micro analyzer （EPMA）. It was observed that the amount of 6-ferrite varied among different grades and also distributed heterogeneously across the width of the steel plates. In general, low nickel ASS showed higher amount of 6-ferrite compared to the standard ASS grades. The tendency to surface cracking during hot rolling gradually increased with increasing 6-ferrite content. Interestingly, carbon and nitrogen exerted maximum effect on 6-ferrite formation. The higher carbon and nitrogen content in the steel decreased 6-ferMte content. In addition, the segregation of Cu and Mn plays significant role in low nickel ASS and Ni-Cr in case of standard ASS has profound effect on surface cracking of the steel plates. A possible cause of surface crack formation/origination in steel plates during hot rolling was discussed.
