Study of hot-workability of titanium alloys through hot-torsion testing and its application to the optimization of forging and extrusion processes

ABSTRACT In the development of hot metal forming, the metallic products must comply with the requirements imposed by current standards. In some cases, the required microstructure can only be obtained through thermomechanical processing. With titanium and its alloys, small ranges of good workability are an additional difficulty. In this work the hot-workability of aeronautical quality titanium alloys was studied through hot torsion and compression testing. The results were used to define the m teri l’s pl stic behaviour seeking to optimize forging and extrusion operating parameters, such as temperature, strain rate, area reduction, etc. Additionally, different processing routes were simulated through hot-torsion testing and the resulting microstructures were analysed and successfully compared to the current standards. At the same time, the minimum amount of area reduction required to obtain such microstructure was determined. The results of hot-workability testing plus the information registered in full-scale Grade 2 Ti extrusion tests were used to simulate different extrusion processes with FEA. To calibrate the FE model it was also necess ry to ev lu te the illet’s temper ture evolution through the press’s feeding system nd the behaviour of the available lubricants. The FE model proved to be accurate to predict the required extrusion force for the tested geometries. This way, the feasibility of extruding different sections was determined and the operating parameters were optimized to maintain the extrusion pressure within operative limits as well as to obtain the m teri l’s properties nd microstructures required in current st nd rds.