Engineering and Technology Journal

The purpose of this study is to study the ultrasonic peening influence upon the mechanical properties of the welded joints of 3 mm AA 7075-T73. Friction stir welding (FSW) was carried out by using milling machine and cylindrical tool with tapered pin. The used welding parameters were 710 rpm , 35 mm min for rotational and travel speed , respectively .Tensile tests results showed that the welding efficiency was about 60% for welded samples , and this value increased by using one and two lines ultrasonic peening treatment to 74% , and 71% , respectively , this improvement is due to generating compressive stresses along the surface of welded joints. The microhardness of the welded samples showed that there were fluctuations across the welded centerline and minimum hardness occur in the heat affected zone (HAZ).

Friction stir processing (FSP) is an innovative technique of varying the metallic features by intense, local plastic deforming. Accordingly, materials are stirred with no altering the phase via melting or otherwise to produce a microstructure with equiaxed and fine grains. This method enhances the microstructural features of metals. In This study the microstructure and the mechanical features including (tensile strength and microhardness), and radiographic inspection results are studied. All specimens of pure copper use in the (FSW) and (FSP) have variable rotating speed (900, 1200, and 1600 rpm) with constant feed speed (40 mm/min). The most remarkable results, the ultimate tensile strength for FSW and FSP at (1200 RPM and 40 mm/min) with the values of 250.4 MPa for FSW and 261..2 MPa for FSP and the efficiency reached 92.7% and 96.3% for FSP and FSW, respectively. The high hardness in the same sample was 118 HV for FSW and 135 HV for FSP. The microstructure at welding zones, specially nugget zone, is improved by the friction stir processing. Radiographic examination showed incomplete fusion of welding joint without defect.

The aim of present study is to investigate the effect of precipitation hardening heat treatment at different aging conditions on the mechanical properties and microstructure of similar friction stir welding (FSW) joints ofAA 2024-T3 and AA 7075-T73 aluminum alloys. Friction stir welding was carried out using milling machine with best welding parameters (tool rotation speed 898 rpm, welding speed 45 mm ̸ min and threaded cylindrical pin geometry). Tensile test, microhardness test,microstructure examination,and X-ray radiographic inspection of FSW joints were made.The results indicated that the best aging conditions for similar welded joints of Al2024 and Al 7075 were in sample (natural aging for two week) and sample
(artificial ageing at 120°C for 24 h) respectively. ‏Microhardness in the as-welded samples showed fluctuations across the weld zone and minimum hardnessoccurs in the heat affected zone(HAZ) in both alloys while the hardness after heat treatment at best aging conditions was improved across the whole weldment and increased in stir zone,

Friction stir welding is a relatively new joining process, which involves the joining of metals without fusion or filler materials. In this study, the effect of tool pin profile on the mechanical properties of aluminum alloys AA2024-T351 joints produced by FSW was investigated. Four different tool pin profiles were developed, (straight cylindrical, taper cylindrical, triangular, and square) to weld the joints. All the welds were produced perpendicularly to the rolling direction for aluminum alloys. Tensile and bending tests were performed to evaluate the mechanical properties by using computerized universal testing machine. Among the four tools, square pin profile gives better tensile strength (265 MPa), elongation (4.9), maximum bending force (1450 N), and maximum welding efficiency (61%) in terms of tensile strength.

The aim of the present work is to investigate the fatigue behavior of friction stir welded joints for dissimilar aluminum alloys (2024 -T3 and 7020-T6). Friction stir welding (FSW) had been done for 6.6 mm thick plate by using NC milling machine with R18 tool steel of 18mm with shoulder diameter and 6mm pin diameter with different tool designs; threaded cone with double bevel, threaded cylinder with concave shoulder of 4°, and beveled cone with concave shoulder of 4°. FSW were carried out under various welding parameters, travel speed of 40, 50, 75 mm/min, rotation speed range (275-1250) rpm and tilt angle of (Ɵ = 3°) with counterclockwise revolution.
Many non- destructive inspections and mechanical tests were performed to evaluate welded joints to determine the best welding parameters. Fatigue test has been done at constant stress amplitude cantilever with stress ratio of (R= -1). The results showed that maximum tensile strength and joint efficiency were 360MPa and 86% respectively for dissimilar joints which were welded at 40mm/min travel speed and 550 rpm rotation speed by using threaded cone with double bevels.

In this study two different welding processes have been considered, a
conventional tungsten inert gas (TIG) and a relatively new solid state welding
known as friction stir welding (FSW). TIG welding process has been performed on
Al 6061-T6 of thickness 4mm by using filler metal of Al-Mg alloy type (ER5356)
according to AWS classification metal with tungsten electrode (EWth-2) and arc
voltage of (12V). Various welding currents of (125, 160, 200, 225) Amp were used
under argon as shielding gas of flow rate of (15-20 cf / hour) and welding speed of
280 mm/min.
Friction stir welding is carried out using automatic milling machine with five
different welding or bed speeds of (25-50-80-100-125 mm/min) and five different
tool rotation speeds of (630-800-1000-1250-1600 rpm). Tool steel of type R18
consists of a shoulder with diameter of (20 mm) and pin of diameter (5.5 mm). Xray
radiographic inspection, tensile test and microhardness test of FSW and TIG
joints at optimum welding conditions were made.
The results indicate that the best tensile strength of FSW joints is 289 MPa and
joint efficiency is 79% which were welded with welding parameters of (1250 rpm,
800 rpm and 50 mm/min, 125 mm/min) respectively. While in case of TIG joint the
best tensile strength is 210 MPa and joint efficiency is 57%.
It was found that the microhardness hardness values in the TIG welded joints
are lower than that of the FSW joints. The formation of fine equiaxed grains and
very fine strengthening precipitates (Mg₂Si) in the stir or weld region are the
reasons for higher tensile strength and hardness of FSW joints compared to TIG
joints.

The present work is aimed to study the friction stir welding and process for the
aluminum alloy 2024-T3, a threaded pin with a diameter of 6 mm and a concaved
shoulder of 18 mm welding tool was used. The single pass friction stir welding
(FSW) process was performed with clockwise tool rotation at different speeds and
variable feeding speeds. The specimens were tested to determine the best ultimate
tensile strength ( ult) and compared with the as received metal. In addition to friction
stir welding (FSW), another phase of welding named friction stir process (FSP) was
used. The best condition out of the FSW variables was selected in order to examine
the double pass welding processes. It was found that the best result is in forward
welding travel and counterclockwise tool rotation. The maximum tensile strength
achieved at friction stir welding process was 72% of the base metal and didn’t
improve in the FSP process. On the other hand, the fatigue endurance limit was
improved for FS weld ment when followed by FSP, where the reduction in fatigue
endurance limit for FSW specimen was 36% while for FSP specimen was 15% of the
base metal.