Spiral defect formation and the factors affecting the mechanical properties of friction welded aluminum Alloy 6061 T6 and 6061/Al 2 O 3 (W6A.10A-T6) composite base materials were investigated. Spiral defects are flow-induced defects formed when material and reinforcing particles transfer to and are trapped in spiral arm regions located near the stationary boundary of friction welded joints. In MMC/MMC joints the spiral defects are Mg-rica and are associated with the segregation of small-diameter Al 2 O 3 particles. When high pressure is applied during 6061/6061 friction welding, the tensile strength properties are improved because of the formation of narrower softened regions on either side of the joint interface. The ratio of the width of the softened region and the tensile-specimen diameter are used to monitor the effect of soitened regions on weld tensile-strength properties. Using this approach, the calculated and experimentally measured joirt tensile-strength properties of 6061/6061 joints are in excellent agreement The improved strengths of MMC/ MMC joints produced using high friction pressures resulted from a combination of factors, namely, 1) decreased numbers of spiral defects in completed joints, 2) material strengthening caused by increased numbers of reinforcing particles in material close to the weld interface and 3) the formation of narrower softened zones adjacent to the weld interface. The tensile strengths of MMC/MMC joints produced using a low friction pressure (60 MPa) were not improved following the application of a T6 solution plus aging postweld heat treatment. In direct contrast, the tensile strengths of postweld heat-treated MMC/MMC joints produced using a friction pressure of 280 MPa were significantly stronger than as-received MMC base material. It is suggested that the different effects produced during postweld heat treatment result from spiral defects acting as sites for preferential failure during notch tensile testing of joints made using low friction pressures.
[1]
T. North,et al.
Mechanical and metallurgical properties of MMC friction welds
,
1997
.
[2]
T. North,et al.
Particle fracture in metal-matrix composite friction joints
,
1997
.
[3]
T. North,et al.
Microstructural features of friction welded MA 956 superalloy material
,
1996
.
[4]
T. North,et al.
Modelling of Viscosity and Fluid Dynamics in Similar Friction Joints
,
1996
.
[5]
Thomas H. North,et al.
Mechanical Properties of Particulate MMC/AISI 304 Friction Joints
,
1995
.
[6]
W. Baeslack,et al.
Inertia-friction welding of particulate-reinforced aluminum matrix composites
,
1994
.
[7]
O. Midling,et al.
A process model for friction welding of AlMgSi alloys and AlSiC metal matrix composites—I. Haz temperature and strain rate distribution
,
1994
.
[8]
K. Kato,et al.
Friction welding of magnesium alloys
,
1994
.
[9]
I. A. Chernenko.
Friction welding AD1 aluminium to 12Kh18N10T steel
,
1989
.
[10]
Kenichi Nakamura,et al.
On Friction Welding
,
1966
.