Abstract
The tensile strength of dissimilar friction welds between 6061 aluminum alloy and S45C carbon steel at high rates of loading is evaluated using a tensile version of the split Hopkinson bar. Round tension specimens are machined from 30 mm diameter friction welded butt joints. Friction welding is carried out using a brake type friction welding machine under fixed welding conditions. All quasi-static and impact tests on the as-welded tension specimens having the weld interface in the middle of the gage length are conducted at room temperature. The test results indicate that the joint tensile strength decreases considerably with increasing loading rate. Macroscopic observations of the fracture surfaces of broken tension specimens reveal that the static fracture takes place in the 6061 aluminum alloy region close to the weld interface, while the impact fracture occurs at the weld interface. The microindentation hardness tests are performed across the weld interface in an attempt to investigate the extent of the heat-affected zone (HAZ) due to friction welding. The microstructure and the distributions of aluminum and iron at the weld interface region are examined with the help of a scanning electron microscope and an electron probe micro-analyzer. The decrease in joint tensile strength with increasing loading rate may be attributed to the presence of very thin brittle intermetallic compounds formed at the weld interface during the friction welding operation.
