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X Cao - One of the best experts on this subject based on the ideXlab platform.
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Residual Stresses and Tensile Properties of Friction Stir Welded AZ31B-H24 Magnesium Alloy in Lap Configuration
Metallurgical and Materials Transactions B, 2015Co-Authors: B S Naik, X Cao, Jacob Friedman, Priti Wanjara, D L ChenAbstract:AZ31B-H24 Mg alloy sheets with a thickness of 2 mm were friction stir welded in lap configuration using two tool Rotational Rates of 1000 and 1500 rpm and two welding speeds of 10 and 20 mm/s. The residual stresses in the longitudinal and transverse directions of the weldments were determined using X-ray diffraction. The shear tensile behavior of the lap joints was evaluated at low [233 K (−40 °C)], room [298 K (25 °C)], and elevated [453 K (180 °C)] temperatures. The failure load was highest for the lower heat input condition that was obtained at a tool Rotational Rate of 1000 rpm and a welding speed of 20 mm/s for all the test temperatures, due to the smaller hooking height, larger effective sheet thickness, and lower tensile residual stresses, as compared to the other two welding conditions that were conducted at a higher tool Rotational Rate or lower welding speed. The lap joints usually fractured on the advancing side of the top sheet near the interface between the thermo-mechanically affected zone and the stir zone. Elevated temperature testing of the weld assembled at a tool Rotational Rate of 1000 rpm and a welding speed of 20 mm/s led to the failure along the sheet interface in shear fracture mode due to the high integrity of the joint that exhibited large plastic deformation and higher total energy absorption.
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Texture Development in a Friction Stir Lap-Welded AZ31B Magnesium Alloy
Metallurgical and Materials Transactions A, 2014Co-Authors: B S Naik, X Cao, D L Chen, Priti WanjaraAbstract:The present study was aimed at characterizing the microstructure, texture, hardness, and tensile properties of an AZ31B-H24 Mg alloy that was friction stir lap welded (FSLWed) at varying tool Rotational Rates and welding speeds. Friction stir lap welding (FSLW) resulted in the presence of recrystallized grains and an associated hardness drop in the stir zone (SZ). Microstructural investigation showed that both the AZ31B-H24 Mg base metal (BM) and SZ contained β-Mg17Al12 and Al8Mn5 second phase particles. The AZ31B-H24 BM contained a type of basal texture (0001)〈11$$ \overline{2} $$2¯0〉 with the (0001) plane nearly parallel to the rolled sheet surface and 〈11$$ \overline{2} $$2¯0〉 directions aligned in the rolling direction. FSLW resulted in the formation of another type of basal texture (0001)〈10$$ \overline{1} $$1¯0〉 in the SZ, where the basal planes (0001) became slightly tilted toward the transverse direction, and the prismatic planes (10$$ \overline{1} $$1¯0) and pyramidal planes (10$$ \overline{1} $$1¯1) exhibited a 30 deg + (n − 1) × 60 deg rotation (n = 1, 2, 3, …) with respect to the rolled sheet normal direction, due to the shear plastic flow near the pin surface that occurred from the intense local stirring. With increasing tool Rotational Rate and decreasing welding speed, the maximum intensity of the basal poles (0001) in the SZ decreased due to a higher degree of dynamic recrystallization that led to a weaker or more random texture. The tool Rotational Rate and welding speed had a strong effect on the failure load of FSLWed joints. A combination of relatively high welding speed (20 mm/s) and low tool Rotational Rate (1000 rpm) was observed to be capable of achieving a high failure load. This was attributed to the relatively small recrystallized grains and high intensity of the basal poles in the SZ arising from the low heat input as well as the presence of a small hooking defect.
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Microstructure and Fatigue Properties of a Friction Stir Lap Welded Magnesium Alloy
Metallurgical and Materials Transactions A, 2013Co-Authors: B S Naik, X Cao, D L Chen, Priti WanjaraAbstract:Friction stir welding (FSW), being an enabling solid-state joining technology, can be suitably applied for the assembly of lightweight magnesium (Mg) alloys. In this investigation, friction stir lap welded (FSLWed) joints of AZ31B-H24 Mg alloy were characterized in terms of the welding defects, microstructure, hardness, and fatigue properties at various combinations of tool Rotational Rates and welding speeds. It was observed that the hardness decreased from the base metal (BM) to the stir zone (SZ) across the heat-affected zone (HAZ) and thermomechanically affected zone (TMAZ). The lowest value of hardness appeared in the SZ. With increasing tool Rotational Rate or decreasing welding speed, the average hardness in the SZ decreased owing to increasing grain size, and a Hall–Petch-type relationship was established. Fatigue fracture of the lap welds always occurred at the interface between the SZ and TMAZ on the advancing side where a larger hooking defect was present (in comparison with the retreating side). The welding parameters had a significant influence on the hook height and the subsequent fatigue life. A relatively “cold” weld, conducted at a Rotational Rate of 1000 rpm and welding speed of 20 mm/s, gave rise to almost complete elimination of the hooking defect, thus considerably (over two orders of magnitude) improving the fatigue life. Fatigue crack propagation was basically characterized by the formation of fatigue striations concomitantly with secondary cracks.
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Friction Stir Welded AZ31 Magnesium Alloy: Microstructure, Texture, and Tensile Properties
Metallurgical and Materials Transactions A, 2013Co-Authors: S. H. Chowdhury, X Cao, D L Chen, S D Bhole, Priti WanjaraAbstract:This study was aimed at characterizing the microstructure, texture and tensile properties of a friction stir welded AZ31B-H24 Mg alloy with varying tool Rotational Rates and welding speeds. Friction stir welding (FSW) resulted in the presence of recrystallized grains and the relevant drop in hardness in the stir zone (SZ). The base alloy contained a strong crystallographic texture with basal planes (0002) largely parallel to the rolling sheet surface and $$ \langle {11\bar{2}0} \rangle $$ directions aligned in the rolling direction (RD). After FSW the basal planes in the SZ were slightly tilted toward the TD determined from the sheet normal direction (or top surface) and also slightly inclined toward the RD determined from the transverse direction (or cross section) due to the intense shear plastic flow near the pin surface. The prismatic planes $$ (10\bar{1}0) $$ and pyramidal planes $$ (10\bar{1}1) $$ formed fiber textures. After FSW both the strength and ductility of the AZ31B-H24 Mg alloy decreased with a joint efficiency in-between about 75 and 82 pct due to the changes in both grain structure and texture, which also weakened the strain Rate dependence of tensile properties. The welding speed and Rotational Rate exhibited a stronger effect on the YS than the UTS. Despite the lower ductility, strain-hardening exponent and hardening capacity, a higher YS was obtained at a higher welding speed and lower Rotational Rate mainly due to the smaller recrystallized grains in the SZ arising from the lower heat input.
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tensile properties of a friction stir welded magnesium alloy effect of pin tool thread orientation and weld pitch
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: S M Chowdhury, D L Chen, S D Bhole, X CaoAbstract:Abstract Microstructures, tensile properties and strain hardening behavior of a friction stir welded (FSWed) AZ31B-H24 magnesium alloy were studied at varying welding speeds, Rotational Rates and pin tool thread orientations. After friction stir welding (FSW) both yield strength (YS) and ultimate tensile strength (UTS) were observed to be lower but strain hardening exponent became much higher due to the presence of recrystallized grains in the stirred zone (SZ) and thermomechanically affected zone (TMAZ). The left-hand thread pin tool rotating clockwise geneRated good FSWed joints and mechanical properties due to the downward material flow close to the pin surface, while the right-hand thread pin tool turning clockwise caused an upward material flow and resulted in inferior joints. The YS and UTS increased and strain hardening exponent decreased with increasing welding speed. The YS as a function of grain sizes obeyed the Hall-Petch relationship well, and it also increased with decreasing Rotational Rate. Both YS and UTS were observed to increase linearly with increasing weld pitch (a ratio of welding speed to Rotational Rate). A significantly higher YS of ∼170 MPa was achieved at a high weld pitch of 1.2 mm/rev, in comparison with that (∼110 MPa) using a weld pitch ranging from 0.0039 to 0.24 mm/rev. All the FSWed AZ31B-H24 joints failed in-between the SZ and TMAZ. Dimple-like ductile fracture characteristics appeared in the base metal, while some cleavage-like flat facets together with dimples and river marking were observed in the FSWed samples.
D L Chen - One of the best experts on this subject based on the ideXlab platform.
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Residual Stresses and Tensile Properties of Friction Stir Welded AZ31B-H24 Magnesium Alloy in Lap Configuration
Metallurgical and Materials Transactions B, 2015Co-Authors: B S Naik, X Cao, Jacob Friedman, Priti Wanjara, D L ChenAbstract:AZ31B-H24 Mg alloy sheets with a thickness of 2 mm were friction stir welded in lap configuration using two tool Rotational Rates of 1000 and 1500 rpm and two welding speeds of 10 and 20 mm/s. The residual stresses in the longitudinal and transverse directions of the weldments were determined using X-ray diffraction. The shear tensile behavior of the lap joints was evaluated at low [233 K (−40 °C)], room [298 K (25 °C)], and elevated [453 K (180 °C)] temperatures. The failure load was highest for the lower heat input condition that was obtained at a tool Rotational Rate of 1000 rpm and a welding speed of 20 mm/s for all the test temperatures, due to the smaller hooking height, larger effective sheet thickness, and lower tensile residual stresses, as compared to the other two welding conditions that were conducted at a higher tool Rotational Rate or lower welding speed. The lap joints usually fractured on the advancing side of the top sheet near the interface between the thermo-mechanically affected zone and the stir zone. Elevated temperature testing of the weld assembled at a tool Rotational Rate of 1000 rpm and a welding speed of 20 mm/s led to the failure along the sheet interface in shear fracture mode due to the high integrity of the joint that exhibited large plastic deformation and higher total energy absorption.
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Texture Development in a Friction Stir Lap-Welded AZ31B Magnesium Alloy
Metallurgical and Materials Transactions A, 2014Co-Authors: B S Naik, X Cao, D L Chen, Priti WanjaraAbstract:The present study was aimed at characterizing the microstructure, texture, hardness, and tensile properties of an AZ31B-H24 Mg alloy that was friction stir lap welded (FSLWed) at varying tool Rotational Rates and welding speeds. Friction stir lap welding (FSLW) resulted in the presence of recrystallized grains and an associated hardness drop in the stir zone (SZ). Microstructural investigation showed that both the AZ31B-H24 Mg base metal (BM) and SZ contained β-Mg17Al12 and Al8Mn5 second phase particles. The AZ31B-H24 BM contained a type of basal texture (0001)〈11$$ \overline{2} $$2¯0〉 with the (0001) plane nearly parallel to the rolled sheet surface and 〈11$$ \overline{2} $$2¯0〉 directions aligned in the rolling direction. FSLW resulted in the formation of another type of basal texture (0001)〈10$$ \overline{1} $$1¯0〉 in the SZ, where the basal planes (0001) became slightly tilted toward the transverse direction, and the prismatic planes (10$$ \overline{1} $$1¯0) and pyramidal planes (10$$ \overline{1} $$1¯1) exhibited a 30 deg + (n − 1) × 60 deg rotation (n = 1, 2, 3, …) with respect to the rolled sheet normal direction, due to the shear plastic flow near the pin surface that occurred from the intense local stirring. With increasing tool Rotational Rate and decreasing welding speed, the maximum intensity of the basal poles (0001) in the SZ decreased due to a higher degree of dynamic recrystallization that led to a weaker or more random texture. The tool Rotational Rate and welding speed had a strong effect on the failure load of FSLWed joints. A combination of relatively high welding speed (20 mm/s) and low tool Rotational Rate (1000 rpm) was observed to be capable of achieving a high failure load. This was attributed to the relatively small recrystallized grains and high intensity of the basal poles in the SZ arising from the low heat input as well as the presence of a small hooking defect.
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microstructure and strain hardening of a friction stir welded high strength al zn mg alloy
Acta Metallurgica Sinica (english Letters), 2014Co-Authors: D L Chen, A H Feng, Z Y, W Y, R J SongAbstract:Microstructural evolution and strain hardening behavior of a friction stir welded (FSWed) high-strength 7075Al-T651 alloy were evaluated. The nugget zone was observed to consist of fine and equiaxed recrystallized grains with a low dislocation density and free of original precipitates, but containing uniformly distributed dispersoids. The strength, joint efficiency, and ductility of the FSWed joints increased with increasing welding speed. A joint efficiency of ~91% was achieved at a welding speed of 400 mm/min and Rotational Rate of 800 r/min, while the ductility remained basically the same as that of the base metal. There was no obvious strain Rate sensitivity observed in both base metal and welded joints. While both the base metal and FSWed joints exhibited stage III and IV hardening characteristics, the hardening capacity, strain hardening exponent, and strain hardening Rate all increased after friction stir welding.
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low cycle fatigue of a friction stir welded 2219 t62 aluminum alloy at different welding parameters and cooling conditions
The International Journal of Advanced Manufacturing Technology, 2014Co-Authors: Junting Liu, D L Chen, G H LuanAbstract:Strain-controlled low-cycle fatigue tests and microstructural evaluation were performed on a friction stir welded 2219-T62 aluminum alloy with varying welding parameters and cooling conditions. Cyclic hardening of friction stir welded joints was appreciably stronger than that of the base material. The cyclic stress amplitude increased, and plastic strain amplitude and fatigue lifetime slightly decreased with increasing welding speed from 60 to 200 mm/min but were only weakly dependent of the Rotational Rate between 300 and 1,000 rpm with air cooling. Friction stir welded joints with water cooling had higher stress amplitude and fatigue life than that with air cooling. Fatigue failure of the joint occurred in the HAZ where the soft zone was present, with crack initiation from the specimen surface or near-surface defect and crack propagation characterized by typical fatigue striations.
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Microstructure and Fatigue Properties of a Friction Stir Lap Welded Magnesium Alloy
Metallurgical and Materials Transactions A, 2013Co-Authors: B S Naik, X Cao, D L Chen, Priti WanjaraAbstract:Friction stir welding (FSW), being an enabling solid-state joining technology, can be suitably applied for the assembly of lightweight magnesium (Mg) alloys. In this investigation, friction stir lap welded (FSLWed) joints of AZ31B-H24 Mg alloy were characterized in terms of the welding defects, microstructure, hardness, and fatigue properties at various combinations of tool Rotational Rates and welding speeds. It was observed that the hardness decreased from the base metal (BM) to the stir zone (SZ) across the heat-affected zone (HAZ) and thermomechanically affected zone (TMAZ). The lowest value of hardness appeared in the SZ. With increasing tool Rotational Rate or decreasing welding speed, the average hardness in the SZ decreased owing to increasing grain size, and a Hall–Petch-type relationship was established. Fatigue fracture of the lap welds always occurred at the interface between the SZ and TMAZ on the advancing side where a larger hooking defect was present (in comparison with the retreating side). The welding parameters had a significant influence on the hook height and the subsequent fatigue life. A relatively “cold” weld, conducted at a Rotational Rate of 1000 rpm and welding speed of 20 mm/s, gave rise to almost complete elimination of the hooking defect, thus considerably (over two orders of magnitude) improving the fatigue life. Fatigue crack propagation was basically characterized by the formation of fatigue striations concomitantly with secondary cracks.
M Ghosh - One of the best experts on this subject based on the ideXlab platform.
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Friction Stir Welding of Steel: Heat Input, Microstructure, and Mechanical Property Co-relation
Journal of Materials Engineering and Performance, 2015Co-Authors: M. Husain, R. Sarkar, Tapan Kumar Pal, N. Prabhu, M GhoshAbstract:Friction stir welding was performed to join carbon steel plates at tool Rotational Rate of 800-1400 rpm. Microstructure and microhardness of welded specimens were evaluated across weld centerline. Torque base index, peak temperature, cooling Rate, strain, strain Rate, volumetric material flow Rate, and width of extruded zone at weld nugget were calculated. Peak temperature at weld nugget was ~1300-1360 K. At this temperature, ferrite transformed to austenite during welding. Austenite was decomposed in to ferrite and bainite at cooling Rate of ~4-7.5 K/s. The presence of bainite was endorsed by increment in microhardness with respect to base material. Ferrite grain size at weld nugget was finer in comparison to as-received alloy. With the increment in tool Rotational Rate strain, strain Rate, total heat input, and peak temperature at weld nugget were increased. High temperature at weld nugget promoted increment in ferrite grain size and reduction in area fraction of bainite. Heat-affected zone also experienced phase transformation and exhibited enhancement in ferrite grain size in comparison to base alloy at all welding parameters with marginal drop in microhardness. Maximum joint strength was obtained at the tool Rotational Rate of 1000 rpm. Increment in tool rational Rate reduced the joint efficiency owing to increment in ferrite grain size and reduction in pearlite area fraction at heat-affected zone.
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Friction Stir-Welded Dissimilar Aluminum Alloys: Microstructure, Mechanical Properties, and Physical State
Journal of Materials Engineering and Performance, 2013Co-Authors: M Ghosh, M. Husain, K Kumar, Satish V. KailasAbstract:A356 and 6061 aluminum alloys were joined by friction stir welding at constant tool Rotational Rate with different tool-traversing speeds. Thermomechanical data of welding showed that increment in tool speed reduced the pseudo heat index and temperature at weld nugget (WN). On the other hand, volume of material within extrusion zone, strain Rate, and Zenner Hollomon parameter were reduced with decrease in tool speed. Optical microstructure of WN exhibited nearly uniform dispersion of Si-rich particles, fine grain size of 6061 Al alloy, and disappearance of second phase within 6061 Al alloy. With enhancement in welding speed, matrix grain size became finer, yet size of Si-rich particles did not reduce incessantly. Size of Si-rich particles was governed by interaction time between tool and substRate. Mechanical property of WN was evaluated. It has been found that the maximum joint efficiency of 116% with respect to that of 6061 alloy was obtained at an intermediate tool-traversing speed, where matrix grain size was significantly fine and those of Si-rich particles were substantially small.
Jan B Talbot - One of the best experts on this subject based on the ideXlab platform.
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electrodeposition of iron group metals and binary alloys from sulfate baths ii modeling
Journal of The Electrochemical Society, 2000Co-Authors: Keith Y Sasaki, Jan B TalbotAbstract:A mechanism of iron‐group elemental metal and binary alloy electrodeposition is proposed. The one‐dimensional diffusion model of Grande and Talbot is used to determine near‐surface concentrations of the ionic species deemed important for electrodeposition; the current model expands upon the surface kinetics by including the effects of competitive adsorption, site blockage by hydrogen atoms, and a variance in the number of adsorption sites. Fitting of the model kinetic parameters to the elemental electrodeposition data was found to simulate the partial current densities extremely well. The proposed model was found to be extensible to the iron‐group binary alloys. Use of the elemental electrodeposition parameters in alloy codeposition was found to effectively characterize the experimental results, e.g., partial current densities, weight fractions, and the effect of electrode Rotational Rate. © 2000 The Electrochemical Society. All rights reserved.
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electrodeposition of iron group metals and binary alloys from sulfate baths i experimental study
Journal of The Electrochemical Society, 1998Co-Authors: Keith Y Sasaki, Jan B TalbotAbstract:Thin films of the iron‐group elemental metals (Ni, Co, and Fe, group VIIIB) and binary alloys (NiCo, CoFe, and NiFe) were galvanostatically electroplated onto a platinum rotating disk electrode from simple sulfate baths. In all cases, the increasing electrode Rotational Rate was found to decrease the partial current densities at a given cathodic potential. Experimental results indicate that for electrodeposition: two distinct Rate‐determining steps exist, partial current densities for metal deposition are not linearly related to bulk metallic concentration, and the partial current densities for hydrogen evolution are found to reach a plateau for each metal sulfate bath and Rotational Rate studied. For the conditions studied, comparison of the partial current densities for elemental and alloy deposition shows that the more noble metal deposition is unchanged or inhibited in alloy codeposition, while that for the less noble metal is promoted.
Priti Wanjara - One of the best experts on this subject based on the ideXlab platform.
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Residual Stresses and Tensile Properties of Friction Stir Welded AZ31B-H24 Magnesium Alloy in Lap Configuration
Metallurgical and Materials Transactions B, 2015Co-Authors: B S Naik, X Cao, Jacob Friedman, Priti Wanjara, D L ChenAbstract:AZ31B-H24 Mg alloy sheets with a thickness of 2 mm were friction stir welded in lap configuration using two tool Rotational Rates of 1000 and 1500 rpm and two welding speeds of 10 and 20 mm/s. The residual stresses in the longitudinal and transverse directions of the weldments were determined using X-ray diffraction. The shear tensile behavior of the lap joints was evaluated at low [233 K (−40 °C)], room [298 K (25 °C)], and elevated [453 K (180 °C)] temperatures. The failure load was highest for the lower heat input condition that was obtained at a tool Rotational Rate of 1000 rpm and a welding speed of 20 mm/s for all the test temperatures, due to the smaller hooking height, larger effective sheet thickness, and lower tensile residual stresses, as compared to the other two welding conditions that were conducted at a higher tool Rotational Rate or lower welding speed. The lap joints usually fractured on the advancing side of the top sheet near the interface between the thermo-mechanically affected zone and the stir zone. Elevated temperature testing of the weld assembled at a tool Rotational Rate of 1000 rpm and a welding speed of 20 mm/s led to the failure along the sheet interface in shear fracture mode due to the high integrity of the joint that exhibited large plastic deformation and higher total energy absorption.
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Texture Development in a Friction Stir Lap-Welded AZ31B Magnesium Alloy
Metallurgical and Materials Transactions A, 2014Co-Authors: B S Naik, X Cao, D L Chen, Priti WanjaraAbstract:The present study was aimed at characterizing the microstructure, texture, hardness, and tensile properties of an AZ31B-H24 Mg alloy that was friction stir lap welded (FSLWed) at varying tool Rotational Rates and welding speeds. Friction stir lap welding (FSLW) resulted in the presence of recrystallized grains and an associated hardness drop in the stir zone (SZ). Microstructural investigation showed that both the AZ31B-H24 Mg base metal (BM) and SZ contained β-Mg17Al12 and Al8Mn5 second phase particles. The AZ31B-H24 BM contained a type of basal texture (0001)〈11$$ \overline{2} $$2¯0〉 with the (0001) plane nearly parallel to the rolled sheet surface and 〈11$$ \overline{2} $$2¯0〉 directions aligned in the rolling direction. FSLW resulted in the formation of another type of basal texture (0001)〈10$$ \overline{1} $$1¯0〉 in the SZ, where the basal planes (0001) became slightly tilted toward the transverse direction, and the prismatic planes (10$$ \overline{1} $$1¯0) and pyramidal planes (10$$ \overline{1} $$1¯1) exhibited a 30 deg + (n − 1) × 60 deg rotation (n = 1, 2, 3, …) with respect to the rolled sheet normal direction, due to the shear plastic flow near the pin surface that occurred from the intense local stirring. With increasing tool Rotational Rate and decreasing welding speed, the maximum intensity of the basal poles (0001) in the SZ decreased due to a higher degree of dynamic recrystallization that led to a weaker or more random texture. The tool Rotational Rate and welding speed had a strong effect on the failure load of FSLWed joints. A combination of relatively high welding speed (20 mm/s) and low tool Rotational Rate (1000 rpm) was observed to be capable of achieving a high failure load. This was attributed to the relatively small recrystallized grains and high intensity of the basal poles in the SZ arising from the low heat input as well as the presence of a small hooking defect.
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Microstructure and Fatigue Properties of a Friction Stir Lap Welded Magnesium Alloy
Metallurgical and Materials Transactions A, 2013Co-Authors: B S Naik, X Cao, D L Chen, Priti WanjaraAbstract:Friction stir welding (FSW), being an enabling solid-state joining technology, can be suitably applied for the assembly of lightweight magnesium (Mg) alloys. In this investigation, friction stir lap welded (FSLWed) joints of AZ31B-H24 Mg alloy were characterized in terms of the welding defects, microstructure, hardness, and fatigue properties at various combinations of tool Rotational Rates and welding speeds. It was observed that the hardness decreased from the base metal (BM) to the stir zone (SZ) across the heat-affected zone (HAZ) and thermomechanically affected zone (TMAZ). The lowest value of hardness appeared in the SZ. With increasing tool Rotational Rate or decreasing welding speed, the average hardness in the SZ decreased owing to increasing grain size, and a Hall–Petch-type relationship was established. Fatigue fracture of the lap welds always occurred at the interface between the SZ and TMAZ on the advancing side where a larger hooking defect was present (in comparison with the retreating side). The welding parameters had a significant influence on the hook height and the subsequent fatigue life. A relatively “cold” weld, conducted at a Rotational Rate of 1000 rpm and welding speed of 20 mm/s, gave rise to almost complete elimination of the hooking defect, thus considerably (over two orders of magnitude) improving the fatigue life. Fatigue crack propagation was basically characterized by the formation of fatigue striations concomitantly with secondary cracks.
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Friction Stir Welded AZ31 Magnesium Alloy: Microstructure, Texture, and Tensile Properties
Metallurgical and Materials Transactions A, 2013Co-Authors: S. H. Chowdhury, X Cao, D L Chen, S D Bhole, Priti WanjaraAbstract:This study was aimed at characterizing the microstructure, texture and tensile properties of a friction stir welded AZ31B-H24 Mg alloy with varying tool Rotational Rates and welding speeds. Friction stir welding (FSW) resulted in the presence of recrystallized grains and the relevant drop in hardness in the stir zone (SZ). The base alloy contained a strong crystallographic texture with basal planes (0002) largely parallel to the rolling sheet surface and $$ \langle {11\bar{2}0} \rangle $$ directions aligned in the rolling direction (RD). After FSW the basal planes in the SZ were slightly tilted toward the TD determined from the sheet normal direction (or top surface) and also slightly inclined toward the RD determined from the transverse direction (or cross section) due to the intense shear plastic flow near the pin surface. The prismatic planes $$ (10\bar{1}0) $$ and pyramidal planes $$ (10\bar{1}1) $$ formed fiber textures. After FSW both the strength and ductility of the AZ31B-H24 Mg alloy decreased with a joint efficiency in-between about 75 and 82 pct due to the changes in both grain structure and texture, which also weakened the strain Rate dependence of tensile properties. The welding speed and Rotational Rate exhibited a stronger effect on the YS than the UTS. Despite the lower ductility, strain-hardening exponent and hardening capacity, a higher YS was obtained at a higher welding speed and lower Rotational Rate mainly due to the smaller recrystallized grains in the SZ arising from the lower heat input.
