Characterization and thermal modelling of friction welded alumina–mild steel with the use of Al 1100 interlayer

This paper reports a study of the physical and thermal behaviors of friction welded alumina–mild steel rods with the use of AL 1100 sheet as interlayer. A series of hardness tests, bending tests, macrostructure observations, SEM and EDX analyses were carried out and were combined with a finite difference thermal model to acquire material parameters. This work demonstrated the insignificant change in the hardness value of the parent alumina and the slight increase in hardness value of the parent mild steel, particularly near the interface region. The bending strength increased with the increase of friction times with the highest bending strength obtained was 186 MPa at 20 s. The fractured surface shows the strong bond at the middle of the interface. The bond was obtained through interfacial interlocking and narrow intermetallic phase formation. However, the incomplete joint observed was detrimental to the joint strength. The thermal profile predictions were compared to actual thermocouple data from welds conducted under identical conditions and were shown to be in fair agreement. Even though the FD method proposed in this study cannot replace a more accurate numerical analysis, it does provide guidance in weld parameter development and allows better understanding of the friction welding process.

Research highlights▶ In this study, continuous drive friction welding was used in which the rotational motion of the workpiece is stopped after pressure has been loaded within a very short period of time (less than 2 s). During the process, the frictional heat was generated in the interface up to a maximum joint heat where plastic deformation was reached rapidly. Then the rotation was stopped to allow the welded joint to cool down freely. In friction welding, four parameters control the character of a weld: rotational speed, relative velocity between the workpieces, frictional time and axial force. These parameters determine the amount of energy input to the weld and the rate of heat generation at the interface. ▶ The purpose of this paper is to define and analyze time–temperature profiles in bonded alumina–mild steel rods during the friction welding process. The FD method was applied in finding the numerical solution. The resulting temperature fields were compared with experimental data and the shortcomings of the method are discussed.