A four stage modelling process has been presented which can beused to accurately represent the thermal and mechanical aspectsof the inertia friction welding process through the use of loadand displacement controlled phases. Thermal results from the firstphase of the model for two different weld parameters have showna significant difference in heating rate between the two weldsand approximately 100◦C difference in interface temperature. Thethermal profile and deformed weld shape at the end of the weld-ing process has been used to predict the residual stresses in the remaining two phases of the model which simulate the post-weldcooling and machining of the finished component. Results fromthe phase volume fields show that the higher weld pressure ofWeld 2 results in a narrower HAZ region which is confirmed bythe predictions and measurement of the residual stress where thecomparison shows that the peak values are well predicted by themodel and in the case of Weld 1, where thermal data is availableto allow calibration of the model, the HAZ width is well pre-dicted. The HAZ width was reduced in the model when a higherpressure was used for the welding, which is consistent with theshifting of the peak in the experimental hole drilling results, how-ever the model overestimated the HAZ width in this case by lessthan 1 mm.