Query: 2195 laser welding

title: Effect of the laser power on the microstructure and mechanical properties of the laser MIG hybrid welding joints of the 2195 Al Li alloy
abstract: In the present study, 2195 aluminium lithium (Al Li) alloy joints were welded by laser metal inert gas (laser MIG) hybrid welding. The effect of different laser powers (700, 1000, and 1300 W) on the microstructures and mechanical properties of the weld joints was investigated. The dendritic solidification structure of the weld joint comprised the a Al, th (Al2Cu) and T (AlLiSi) phases. When the laser power increased, the grains coarsened, and the amount of the precipitated phase decreased. Consequently, the micro hardness of the weld decreased. The heat input also increased with the increase in laser power. This increased the fluidity and solidification time of the liquid metal at the bottom of the molten pool. Therefore, the deposition of the particles of the refractory metal compounds and the formation of the equiaxed grain zone (EQZ) was hindered.

title: Influence of post weld heat treatment on microstructure and mechanical properties of laser beam welded 2195 Al Li alloy
abstract: 2195 Al Li alloy is welded by using laser beam welding (LBW) Subsequently, the welded joints are treated by solution treatment at 520 degC for 1 h, then aging treatments with different procedures. The influence of post weld heat treatment (PWHT) on microstructure and mechanical properties of the welded joint is systematically investigated. Optical microscope (OM) scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) transmission electron microscope (TEM) and x ray diffractometer (XRD) are used to characterize the microstructure of joints respectively. The tensile strength and microhardness of welded joints before and after PWHT are evaluated respectively. Results show that, after post weld double aging treatment (HT3) the tensile strength of welded joint is 485.2 MPa, which is 89.03% of that of base metal. Microstructural analysis indicates that the fine equiaxed grain zone (EQZ) near fusion line disappears after HT3. The precipitation of strengthening phases such as T1(Al2CuLi) phase is promoted by PWHT both near grain boundaries and in Al matrix. Moreover, the microstructure of weldment is refined after HT3, thus the ductility of welded joint is improved to a certain extent.

title: A Fundamental Study of Laser Beam Welding Aluminum Lithium Alloy 2195 for Cryogenic Tank Applications
abstract: Based on the potential for decreasing costs of joining stiffeners to skin by laser beam welding, a fundamental researchprogram was conducted toaddresstheimpediments identifieduringan initial studyinvolvinglaserbeam welding of aluminum lithiumalloys.Initial objectivesof theprogram were the identificationf governing mechanism responsibleforprocessrelatedporositywhile establishing a multivariant relationship between process parameters and fusion zone geometry for laser beam welds of alloy 2195 (A1 4.0Cu I.0Li 0.4Mg 0.4Ag) A 14 kW CO 2 laser and the Laser Articulating Robotic System were used to produce all laser beam welds. The lap joint configuration utilized during the study entailed welding 1.25 mm (0.050 in. thick 2195 T6 to 3.12 mm (0.125 in. thick 2195 T8 and was selected to simulate stiffeners to skin for stiffened panel applications. Transmission electron microscopy was performed to characterize the 2195 T8 base material and heat affected zone. The base metal microstructure of this alloy in the peak aged temper was found to be dominated by T 1 (A12CuLi) and 0' (A12Cu) precipitates. The gradual loss of strength for positions representing the heat affected zone is believed to be attributed to dissolution of the T1 precipitate. A narrow region of the heat affected zone that is adjacent to the fusion zone interface may influence weld toughness by the presence of precipitate free zones and solute depletion. A three level fractional factorial experiment was conducted to establish quantitative relationships between primary laser beam processing parameters and critical weld attributes. Strong statistical correlation was observed for weld penetration as a function of welding velocity and stand off distance, weld width at the interface as a function of stand off distance, and porosi_ ratin, g as a function of amount removed by chemical milling and welding velocity. Parameters identified for optimal conditions were: an output power of 10 kW, a processing speed of 10.6 cm/s (250 IPM) a stand off distance of 13.3 cm (5.25 in. and chemical milling of 0.25 mm (0.010 in. per side prior to welding. These parameters were utilized during a reproducibility study to ascertain process consistency. Although process consistency appeared high for welds produced during partial completion of this study, numerous cracks on the top surface of the welds were discovered during visual inspection and necessitated additional investigations concerning weld cracking. A crack sensitivity study was performed to identify possible means of reducing or eliminating cracks within the laser beam welds of 2195. Two experiments were conducted to assess the effect of frier alloy additions on crack sensitivity: the f_t experiment was used to ascertain the effects of various frier alloys on cracking and the second experiment involved modification to process parameters for increasing filler metal dilution. Filler alloys 2319 (AI 6.3 Cu) 4043 (A1 5.3Si) 4047 (AI 12Si) 4145 (AI 10Si 4Cu) and 5356 (A1 5.0Mg) were evaluated for reducing crack susceptibility. Process parameters used during this experiment were identical to those established during the parametric study, except for the addition of filler metal. Results indicated that ftller alloys 4047 and 4145 showed promise for eliminating weld cracking; however, increased frier metal dilution was believed to be necessary for eliminating cracking. Increased dilution would requiremodificationstothe establishedprocessparameters..Process.parametc_were idcn._ed for increasingfiller metal dilutionbutmaintainingweld penctranon reqmrements, parameters mat provided theminimal amount of crackingwhile controllingpenetralaonintothe skin sheetwere 10.3kW of power, 7.9 cm/s (150 IPM) travelspeed,stand offdistanceof 1.55mm (0.062in. above focus,and a wire feedspeed of 15.8cm/s (300 IPM) Although the frequency of solidification crackswas reduced with theseparameters,solidification crackingcould not be eliminated.Parametersthatresultedinincreasedlevelsof fiUcradditionwere alsofound tobe contrarytotheparametricwindow establishedforoptimizingweld profileand pool stability. Although weld cracking was not eliminated, two panels representing laser beam lap welds were produced using 4047 filler metal and the modified process parameters for abbreviated mechanical property testing at NASA Langley Research Center.

title: A Fundamental Study of Laser Beam Welding Aluminum Lithium Alloy 2195 for Cryogenic Tank Applications
abstract: Based on the potential for decreasing costs of joining stiffeners to skin by laser beam welding, a fundamental researchprogram was conducted toaddresstheimpediments identifieduringan initial studyinvolvinglaserbeam welding of aluminum lithiumalloys.Initial objectivesof theprogram were the identificationf governing mechanism responsibleforprocessrelatedporositywhile establishing a multivariant relationship between process parameters and fusion zone geometry for laser beam welds of alloy 2195 (A1 4.0Cu I.0Li 0.4Mg 0.4Ag) A 14 kW CO 2 laser and the Laser Articulating Robotic System were used to produce all laser beam welds. The lap joint configuration utilized during the study entailed welding 1.25 mm (0.050 in. thick 2195 T6 to 3.12 mm (0.125 in. thick 2195 T8 and was selected to simulate stiffeners to skin for stiffened panel applications. Transmission electron microscopy was performed to characterize the 2195 T8 base material and heat affected zone. The base metal microstructure of this alloy in the peak aged temper was found to be dominated by T 1 (A12CuLi) and 0' (A12Cu) precipitates. The gradual loss of strength for positions representing the heat affected zone is believed to be attributed to dissolution of the T1 precipitate. A narrow region of the heat affected zone that is adjacent to the fusion zone interface may influence weld toughness by the presence of precipitate free zones and solute depletion. A three level fractional factorial experiment was conducted to establish quantitative relationships between primary laser beam processing parameters and critical weld attributes. Strong statistical correlation was observed for weld penetration as a function of welding velocity and stand off distance, weld width at the interface as a function of stand off distance, and porosi_ ratin, g as a function of amount removed by chemical milling and welding velocity. Parameters identified for optimal conditions were: an output power of 10 kW, a processing speed of 10.6 cm/s (250 IPM) a stand off distance of 13.3 cm (5.25 in. and chemical milling of 0.25 mm (0.010 in. per side prior to welding. These parameters were utilized during a reproducibility study to ascertain process consistency. Although process consistency appeared high for welds produced during partial completion of this study, numerous cracks on the top surface of the welds were discovered during visual inspection and necessitated additional investigations concerning weld cracking. A crack sensitivity study was performed to identify possible means of reducing or eliminating cracks within the laser beam welds of 2195. Two experiments were conducted to assess the effect of frier alloy additions on crack sensitivity: the f_t experiment was used to ascertain the effects of various frier alloys on cracking and the second experiment involved modification to process parameters for increasing filler metal dilution. Filler alloys 2319 (AI 6.3 Cu) 4043 (A1 5.3Si) 4047 (AI 12Si) 4145 (AI 10Si 4Cu) and 5356 (A1 5.0Mg) were evaluated for reducing crack susceptibility. Process parameters used during this experiment were identical to those established during the parametric study, except for the addition of filler metal. Results indicated that ftller alloys 4047 and 4145 showed promise for eliminating weld cracking; however, increased frier metal dilution was believed to be necessary for eliminating cracking. Increased dilution would requiremodificationstothe establishedprocessparameters..Process.parametc_were idcn._ed for increasingfiller metal dilutionbutmaintainingweld penctranon reqmrements, parameters mat provided theminimal amount of crackingwhile controllingpenetralaonintothe skin sheetwere 10.3kW of power, 7.9 cm/s (150 IPM) travelspeed,stand offdistanceof 1.55mm (0.062in. above focus,and a wire feedspeed of 15.8cm/s (300 IPM) Although the frequency of solidification crackswas reduced with theseparameters,solidification crackingcould not be eliminated.Parametersthatresultedinincreasedlevelsof fiUcradditionwere alsofound tobe contrarytotheparametricwindow establishedforoptimizingweld profileand pool stability. Although weld cracking was not eliminated, two panels representing laser beam lap welds were produced using 4047 filler metal and the modified process parameters for abbreviated mechanical property testing at NASA Langley Research Center.

title: A Fundamental Study of Laser Beam Welding Aluminum Lithium Alloy 2195 for Cryogenic Tank Applications
abstract: Based on the potential for decreasing costs of joining stiffeners to skin by laser beam welding, a fundamental researchprogram was conducted toaddresstheimpediments identifieduringan initial studyinvolvinglaserbeam welding of aluminum lithiumalloys.Initial objectivesof theprogram were the identificationf governing mechanism responsibleforprocessrelatedporositywhile establishing a multivariant relationship between process parameters and fusion zone geometry for laser beam welds of alloy 2195 (A1 4.0Cu I.0Li 0.4Mg 0.4Ag) A 14 kW CO 2 laser and the Laser Articulating Robotic System were used to produce all laser beam welds. The lap joint configuration utilized during the study entailed welding 1.25 mm (0.050 in. thick 2195 T6 to 3.12 mm (0.125 in. thick 2195 T8 and was selected to simulate stiffeners to skin for stiffened panel applications. Transmission electron microscopy was performed to characterize the 2195 T8 base material and heat affected zone. The base metal microstructure of this alloy in the peak aged temper was found to be dominated by T 1 (A12CuLi) and 0' (A12Cu) precipitates. The gradual loss of strength for positions representing the heat affected zone is believed to be attributed to dissolution of the T1 precipitate. A narrow region of the heat affected zone that is adjacent to the fusion zone interface may influence weld toughness by the presence of precipitate free zones and solute depletion. A three level fractional factorial experiment was conducted to establish quantitative relationships between primary laser beam processing parameters and critical weld attributes. Strong statistical correlation was observed for weld penetration as a function of welding velocity and stand off distance, weld width at the interface as a function of stand off distance, and porosi_ ratin, g as a function of amount removed by chemical milling and welding velocity. Parameters identified for optimal conditions were: an output power of 10 kW, a processing speed of 10.6 cm/s (250 IPM) a stand off distance of 13.3 cm (5.25 in. and chemical milling of 0.25 mm (0.010 in. per side prior to welding. These parameters were utilized during a reproducibility study to ascertain process consistency. Although process consistency appeared high for welds produced during partial completion of this study, numerous cracks on the top surface of the welds were discovered during visual inspection and necessitated additional investigations concerning weld cracking. A crack sensitivity study was performed to identify possible means of reducing or eliminating cracks within the laser beam welds of 2195. Two experiments were conducted to assess the effect of frier alloy additions on crack sensitivity: the f_t experiment was used to ascertain the effects of various frier alloys on cracking and the second experiment involved modification to process parameters for increasing filler metal dilution. Filler alloys 2319 (AI 6.3 Cu) 4043 (A1 5.3Si) 4047 (AI 12Si) 4145 (AI 10Si 4Cu) and 5356 (A1 5.0Mg) were evaluated for reducing crack susceptibility. Process parameters used during this experiment were identical to those established during the parametric study, except for the addition of filler metal. Results indicated that ftller alloys 4047 and 4145 showed promise for eliminating weld cracking; however, increased frier metal dilution was believed to be necessary for eliminating cracking. Increased dilution would requiremodificationstothe establishedprocessparameters..Process.parametc_were idcn._ed for increasingfiller metal dilutionbutmaintainingweld penctranon reqmrements, parameters mat provided theminimal amount of crackingwhile controllingpenetralaonintothe skin sheetwere 10.3kW of power, 7.9 cm/s (150 IPM) travelspeed,stand offdistanceof 1.55mm (0.062in. above focus,and a wire feedspeed of 15.8cm/s (300 IPM) Although the frequency of solidification crackswas reduced with theseparameters,solidification crackingcould not be eliminated.Parametersthatresultedinincreasedlevelsof fiUcradditionwere alsofound tobe contrarytotheparametricwindow establishedforoptimizingweld profileand pool stability. Although weld cracking was not eliminated, two panels representing laser beam lap welds were produced using 4047 filler metal and the modified process parameters for abbreviated mechanical property testing at NASA Langley Research Center.

title: A Fundamental Study of Laser Beam Welding Aluminum Lithium Alloy 2195 for Cryogenic Tank Applications
abstract: Based on the potential for decreasing costs of joining stiffeners to skin by laser beam welding, a fundamental researchprogram was conducted toaddresstheimpediments identifieduringan initial studyinvolvinglaserbeam welding of aluminum lithiumalloys.Initial objectivesof theprogram were the identificationf governing mechanism responsibleforprocessrelatedporositywhile establishing a multivariant relationship between process parameters and fusion zone geometry for laser beam welds of alloy 2195 (A1 4.0Cu I.0Li 0.4Mg 0.4Ag) A 14 kW CO 2 laser and the Laser Articulating Robotic System were used to produce all laser beam welds. The lap joint configuration utilized during the study entailed welding 1.25 mm (0.050 in. thick 2195 T6 to 3.12 mm (0.125 in. thick 2195 T8 and was selected to simulate stiffeners to skin for stiffened panel applications. Transmission electron microscopy was performed to characterize the 2195 T8 base material and heat affected zone. The base metal microstructure of this alloy in the peak aged temper was found to be dominated by T 1 (A12CuLi) and 0' (A12Cu) precipitates. The gradual loss of strength for positions representing the heat affected zone is believed to be attributed to dissolution of the T1 precipitate. A narrow region of the heat affected zone that is adjacent to the fusion zone interface may influence weld toughness by the presence of precipitate free zones and solute depletion. A three level fractional factorial experiment was conducted to establish quantitative relationships between primary laser beam processing parameters and critical weld attributes. Strong statistical correlation was observed for weld penetration as a function of welding velocity and stand off distance, weld width at the interface as a function of stand off distance, and porosi_ ratin, g as a function of amount removed by chemical milling and welding velocity. Parameters identified for optimal conditions were: an output power of 10 kW, a processing speed of 10.6 cm/s (250 IPM) a stand off distance of 13.3 cm (5.25 in. and chemical milling of 0.25 mm (0.010 in. per side prior to welding. These parameters were utilized during a reproducibility study to ascertain process consistency. Although process consistency appeared high for welds produced during partial completion of this study, numerous cracks on the top surface of the welds were discovered during visual inspection and necessitated additional investigations concerning weld cracking. A crack sensitivity study was performed to identify possible means of reducing or eliminating cracks within the laser beam welds of 2195. Two experiments were conducted to assess the effect of frier alloy additions on crack sensitivity: the f_t experiment was used to ascertain the effects of various frier alloys on cracking and the second experiment involved modification to process parameters for increasing filler metal dilution. Filler alloys 2319 (AI 6.3 Cu) 4043 (A1 5.3Si) 4047 (AI 12Si) 4145 (AI 10Si 4Cu) and 5356 (A1 5.0Mg) were evaluated for reducing crack susceptibility. Process parameters used during this experiment were identical to those established during the parametric study, except for the addition of filler metal. Results indicated that ftller alloys 4047 and 4145 showed promise for eliminating weld cracking; however, increased frier metal dilution was believed to be necessary for eliminating cracking. Increased dilution would requiremodificationstothe establishedprocessparameters..Process.parametc_were idcn._ed for increasingfiller metal dilutionbutmaintainingweld penctranon reqmrements, parameters mat provided theminimal amount of crackingwhile controllingpenetralaonintothe skin sheetwere 10.3kW of power, 7.9 cm/s (150 IPM) travelspeed,stand offdistanceof 1.55mm (0.062in. above focus,and a wire feedspeed of 15.8cm/s (300 IPM) Although the frequency of solidification crackswas reduced with theseparameters,solidification crackingcould not be eliminated.Parametersthatresultedinincreasedlevelsof fiUcradditionwere alsofound tobe contrarytotheparametricwindow establishedforoptimizingweld profileand pool stability. Although weld cracking was not eliminated, two panels representing laser beam lap welds were produced using 4047 filler metal and the modified process parameters for abbreviated mechanical property testing at NASA Langley Research Center.

title: A Fundamental Study of Laser Beam Welding Aluminum Lithium Alloy 2195 for Cryogenic Tank Applications
abstract: Based on the potential for decreasing costs of joining stiffeners to skin by laser beam welding, a fundamental researchprogram was conducted toaddresstheimpediments identifieduringan initial studyinvolvinglaserbeam welding of aluminum lithiumalloys.Initial objectivesof theprogram were the identificationf governing mechanism responsibleforprocessrelatedporositywhile establishing a multivariant relationship between process parameters and fusion zone geometry for laser beam welds of alloy 2195 (A1 4.0Cu I.0Li 0.4Mg 0.4Ag) A 14 kW CO 2 laser and the Laser Articulating Robotic System were used to produce all laser beam welds. The lap joint configuration utilized during the study entailed welding 1.25 mm (0.050 in. thick 2195 T6 to 3.12 mm (0.125 in. thick 2195 T8 and was selected to simulate stiffeners to skin for stiffened panel applications. Transmission electron microscopy was performed to characterize the 2195 T8 base material and heat affected zone. The base metal microstructure of this alloy in the peak aged temper was found to be dominated by T 1 (A12CuLi) and 0' (A12Cu) precipitates. The gradual loss of strength for positions representing the heat affected zone is believed to be attributed to dissolution of the T1 precipitate. A narrow region of the heat affected zone that is adjacent to the fusion zone interface may influence weld toughness by the presence of precipitate free zones and solute depletion. A three level fractional factorial experiment was conducted to establish quantitative relationships between primary laser beam processing parameters and critical weld attributes. Strong statistical correlation was observed for weld penetration as a function of welding velocity and stand off distance, weld width at the interface as a function of stand off distance, and porosi_ ratin, g as a function of amount removed by chemical milling and welding velocity. Parameters identified for optimal conditions were: an output power of 10 kW, a processing speed of 10.6 cm/s (250 IPM) a stand off distance of 13.3 cm (5.25 in. and chemical milling of 0.25 mm (0.010 in. per side prior to welding. These parameters were utilized during a reproducibility study to ascertain process consistency. Although process consistency appeared high for welds produced during partial completion of this study, numerous cracks on the top surface of the welds were discovered during visual inspection and necessitated additional investigations concerning weld cracking. A crack sensitivity study was performed to identify possible means of reducing or eliminating cracks within the laser beam welds of 2195. Two experiments were conducted to assess the effect of frier alloy additions on crack sensitivity: the f_t experiment was used to ascertain the effects of various frier alloys on cracking and the second experiment involved modification to process parameters for increasing filler metal dilution. Filler alloys 2319 (AI 6.3 Cu) 4043 (A1 5.3Si) 4047 (AI 12Si) 4145 (AI 10Si 4Cu) and 5356 (A1 5.0Mg) were evaluated for reducing crack susceptibility. Process parameters used during this experiment were identical to those established during the parametric study, except for the addition of filler metal. Results indicated that ftller alloys 4047 and 4145 showed promise for eliminating weld cracking; however, increased frier metal dilution was believed to be necessary for eliminating cracking. Increased dilution would requiremodificationstothe establishedprocessparameters..Process.parametc_were idcn._ed for increasingfiller metal dilutionbutmaintainingweld penctranon reqmrements, parameters mat provided theminimal amount of crackingwhile controllingpenetralaonintothe skin sheetwere 10.3kW of power, 7.9 cm/s (150 IPM) travelspeed,stand offdistanceof 1.55mm (0.062in. above focus,and a wire feedspeed of 15.8cm/s (300 IPM) Although the frequency of solidification crackswas reduced with theseparameters,solidification crackingcould not be eliminated.Parametersthatresultedinincreasedlevelsof fiUcradditionwere alsofound tobe contrarytotheparametricwindow establishedforoptimizingweld profileand pool stability. Although weld cracking was not eliminated, two panels representing laser beam lap welds were produced using 4047 filler metal and the modified process parameters for abbreviated mechanical property testing at NASA Langley Research Center.

title: A Fundamental Study of Laser Beam Welding Aluminum Lithium Alloy 2195 for Cryogenic Tank Applications
abstract: Based on the potential for decreasing costs of joining stiffeners to skin by laser beam welding, a fundamental researchprogram was conducted toaddresstheimpediments identifieduringan initial studyinvolvinglaserbeam welding of aluminum lithiumalloys.Initial objectivesof theprogram were the identificationf governing mechanism responsibleforprocessrelatedporositywhile establishing a multivariant relationship between process parameters and fusion zone geometry for laser beam welds of alloy 2195 (A1 4.0Cu I.0Li 0.4Mg 0.4Ag) A 14 kW CO 2 laser and the Laser Articulating Robotic System were used to produce all laser beam welds. The lap joint configuration utilized during the study entailed welding 1.25 mm (0.050 in. thick 2195 T6 to 3.12 mm (0.125 in. thick 2195 T8 and was selected to simulate stiffeners to skin for stiffened panel applications. Transmission electron microscopy was performed to characterize the 2195 T8 base material and heat affected zone. The base metal microstructure of this alloy in the peak aged temper was found to be dominated by T 1 (A12CuLi) and 0' (A12Cu) precipitates. The gradual loss of strength for positions representing the heat affected zone is believed to be attributed to dissolution of the T1 precipitate. A narrow region of the heat affected zone that is adjacent to the fusion zone interface may influence weld toughness by the presence of precipitate free zones and solute depletion. A three level fractional factorial experiment was conducted to establish quantitative relationships between primary laser beam processing parameters and critical weld attributes. Strong statistical correlation was observed for weld penetration as a function of welding velocity and stand off distance, weld width at the interface as a function of stand off distance, and porosi_ ratin, g as a function of amount removed by chemical milling and welding velocity. Parameters identified for optimal conditions were: an output power of 10 kW, a processing speed of 10.6 cm/s (250 IPM) a stand off distance of 13.3 cm (5.25 in. and chemical milling of 0.25 mm (0.010 in. per side prior to welding. These parameters were utilized during a reproducibility study to ascertain process consistency. Although process consistency appeared high for welds produced during partial completion of this study, numerous cracks on the top surface of the welds were discovered during visual inspection and necessitated additional investigations concerning weld cracking. A crack sensitivity study was performed to identify possible means of reducing or eliminating cracks within the laser beam welds of 2195. Two experiments were conducted to assess the effect of frier alloy additions on crack sensitivity: the f_t experiment was used to ascertain the effects of various frier alloys on cracking and the second experiment involved modification to process parameters for increasing filler metal dilution. Filler alloys 2319 (AI 6.3 Cu) 4043 (A1 5.3Si) 4047 (AI 12Si) 4145 (AI 10Si 4Cu) and 5356 (A1 5.0Mg) were evaluated for reducing crack susceptibility. Process parameters used during this experiment were identical to those established during the parametric study, except for the addition of filler metal. Results indicated that ftller alloys 4047 and 4145 showed promise for eliminating weld cracking; however, increased frier metal dilution was believed to be necessary for eliminating cracking. Increased dilution would requiremodificationstothe establishedprocessparameters..Process.parametc_were idcn._ed for increasingfiller metal dilutionbutmaintainingweld penctranon reqmrements, parameters mat provided theminimal amount of crackingwhile controllingpenetralaonintothe skin sheetwere 10.3kW of power, 7.9 cm/s (150 IPM) travelspeed,stand offdistanceof 1.55mm (0.062in. above focus,and a wire feedspeed of 15.8cm/s (300 IPM) Although the frequency of solidification crackswas reduced with theseparameters,solidification crackingcould not be eliminated.Parametersthatresultedinincreasedlevelsof fiUcradditionwere alsofound tobe contrarytotheparametricwindow establishedforoptimizingweld profileand pool stability. Although weld cracking was not eliminated, two panels representing laser beam lap welds were produced using 4047 filler metal and the modified process parameters for abbreviated mechanical property testing at NASA Langley Research Center.

title: A Fundamental Study of Laser Beam Welding Aluminum Lithium Alloy 2195 for Cryogenic Tank Applications
abstract: Based on the potential for decreasing costs of joining stiffeners to skin by laser beam welding, a fundamental researchprogram was conducted toaddresstheimpediments identifieduringan initial studyinvolvinglaserbeam welding of aluminum lithiumalloys.Initial objectivesof theprogram were the identificationf governing mechanism responsibleforprocessrelatedporositywhile establishing a multivariant relationship between process parameters and fusion zone geometry for laser beam welds of alloy 2195 (A1 4.0Cu I.0Li 0.4Mg 0.4Ag) A 14 kW CO 2 laser and the Laser Articulating Robotic System were used to produce all laser beam welds. The lap joint configuration utilized during the study entailed welding 1.25 mm (0.050 in. thick 2195 T6 to 3.12 mm (0.125 in. thick 2195 T8 and was selected to simulate stiffeners to skin for stiffened panel applications. Transmission electron microscopy was performed to characterize the 2195 T8 base material and heat affected zone. The base metal microstructure of this alloy in the peak aged temper was found to be dominated by T 1 (A12CuLi) and 0' (A12Cu) precipitates. The gradual loss of strength for positions representing the heat affected zone is believed to be attributed to dissolution of the T1 precipitate. A narrow region of the heat affected zone that is adjacent to the fusion zone interface may influence weld toughness by the presence of precipitate free zones and solute depletion. A three level fractional factorial experiment was conducted to establish quantitative relationships between primary laser beam processing parameters and critical weld attributes. Strong statistical correlation was observed for weld penetration as a function of welding velocity and stand off distance, weld width at the interface as a function of stand off distance, and porosi_ ratin, g as a function of amount removed by chemical milling and welding velocity. Parameters identified for optimal conditions were: an output power of 10 kW, a processing speed of 10.6 cm/s (250 IPM) a stand off distance of 13.3 cm (5.25 in. and chemical milling of 0.25 mm (0.010 in. per side prior to welding. These parameters were utilized during a reproducibility study to ascertain process consistency. Although process consistency appeared high for welds produced during partial completion of this study, numerous cracks on the top surface of the welds were discovered during visual inspection and necessitated additional investigations concerning weld cracking. A crack sensitivity study was performed to identify possible means of reducing or eliminating cracks within the laser beam welds of 2195. Two experiments were conducted to assess the effect of frier alloy additions on crack sensitivity: the f_t experiment was used to ascertain the effects of various frier alloys on cracking and the second experiment involved modification to process parameters for increasing filler metal dilution. Filler alloys 2319 (AI 6.3 Cu) 4043 (A1 5.3Si) 4047 (AI 12Si) 4145 (AI 10Si 4Cu) and 5356 (A1 5.0Mg) were evaluated for reducing crack susceptibility. Process parameters used during this experiment were identical to those established during the parametric study, except for the addition of filler metal. Results indicated that ftller alloys 4047 and 4145 showed promise for eliminating weld cracking; however, increased frier metal dilution was believed to be necessary for eliminating cracking. Increased dilution would requiremodificationstothe establishedprocessparameters..Process.parametc_were idcn._ed for increasingfiller metal dilutionbutmaintainingweld penctranon reqmrements, parameters mat provided theminimal amount of crackingwhile controllingpenetralaonintothe skin sheetwere 10.3kW of power, 7.9 cm/s (150 IPM) travelspeed,stand offdistanceof 1.55mm (0.062in. above focus,and a wire feedspeed of 15.8cm/s (300 IPM) Although the frequency of solidification crackswas reduced with theseparameters,solidification crackingcould not be eliminated.Parametersthatresultedinincreasedlevelsof fiUcradditionwere alsofound tobe contrarytotheparametricwindow establishedforoptimizingweld profileand pool stability. Although weld cracking was not eliminated, two panels representing laser beam lap welds were produced using 4047 filler metal and the modified process parameters for abbreviated mechanical property testing at NASA Langley Research Center.

title: A Fundamental Study of Laser Beam Welding Aluminum Lithium Alloy 2195 for Cryogenic Tank Applications
abstract: Based on the potential for decreasing costs of joining stiffeners to skin by laser beam welding, a fundamental researchprogram was conducted toaddresstheimpediments identifieduringan initial studyinvolvinglaserbeam welding of aluminum lithiumalloys.Initial objectivesof theprogram were the identificationf governing mechanism responsibleforprocessrelatedporositywhile establishing a multivariant relationship between process parameters and fusion zone geometry for laser beam welds of alloy 2195 (A1 4.0Cu I.0Li 0.4Mg 0.4Ag) A 14 kW CO 2 laser and the Laser Articulating Robotic System were used to produce all laser beam welds. The lap joint configuration utilized during the study entailed welding 1.25 mm (0.050 in. thick 2195 T6 to 3.12 mm (0.125 in. thick 2195 T8 and was selected to simulate stiffeners to skin for stiffened panel applications. Transmission electron microscopy was performed to characterize the 2195 T8 base material and heat affected zone. The base metal microstructure of this alloy in the peak aged temper was found to be dominated by T 1 (A12CuLi) and 0' (A12Cu) precipitates. The gradual loss of strength for positions representing the heat affected zone is believed to be attributed to dissolution of the T1 precipitate. A narrow region of the heat affected zone that is adjacent to the fusion zone interface may influence weld toughness by the presence of precipitate free zones and solute depletion. A three level fractional factorial experiment was conducted to establish quantitative relationships between primary laser beam processing parameters and critical weld attributes. Strong statistical correlation was observed for weld penetration as a function of welding velocity and stand off distance, weld width at the interface as a function of stand off distance, and porosi_ ratin, g as a function of amount removed by chemical milling and welding velocity. Parameters identified for optimal conditions were: an output power of 10 kW, a processing speed of 10.6 cm/s (250 IPM) a stand off distance of 13.3 cm (5.25 in. and chemical milling of 0.25 mm (0.010 in. per side prior to welding. These parameters were utilized during a reproducibility study to ascertain process consistency. Although process consistency appeared high for welds produced during partial completion of this study, numerous cracks on the top surface of the welds were discovered during visual inspection and necessitated additional investigations concerning weld cracking. A crack sensitivity study was performed to identify possible means of reducing or eliminating cracks within the laser beam welds of 2195. Two experiments were conducted to assess the effect of frier alloy additions on crack sensitivity: the f_t experiment was used to ascertain the effects of various frier alloys on cracking and the second experiment involved modification to process parameters for increasing filler metal dilution. Filler alloys 2319 (AI 6.3 Cu) 4043 (A1 5.3Si) 4047 (AI 12Si) 4145 (AI 10Si 4Cu) and 5356 (A1 5.0Mg) were evaluated for reducing crack susceptibility. Process parameters used during this experiment were identical to those established during the parametric study, except for the addition of filler metal. Results indicated that ftller alloys 4047 and 4145 showed promise for eliminating weld cracking; however, increased frier metal dilution was believed to be necessary for eliminating cracking. Increased dilution would requiremodificationstothe establishedprocessparameters..Process.parametc_were idcn._ed for increasingfiller metal dilutionbutmaintainingweld penctranon reqmrements, parameters mat provided theminimal amount of crackingwhile controllingpenetralaonintothe skin sheetwere 10.3kW of power, 7.9 cm/s (150 IPM) travelspeed,stand offdistanceof 1.55mm (0.062in. above focus,and a wire feedspeed of 15.8cm/s (300 IPM) Although the frequency of solidification crackswas reduced with theseparameters,solidification crackingcould not be eliminated.Parametersthatresultedinincreasedlevelsof fiUcradditionwere alsofound tobe contrarytotheparametricwindow establishedforoptimizingweld profileand pool stability. Although weld cracking was not eliminated, two panels representing laser beam lap welds were produced using 4047 filler metal and the modified process parameters for abbreviated mechanical property testing at NASA Langley Research Center.