Ductile Fracture Limits of the CuZn40Pb2 Brass Alloy Deformed at Elevated Temperature

The effectiveness of predicting the fracture occurrence in forging process chains strongly depends on the correct choice and calibration of damage and fracture laws under specific stress and strain conditions. The objective of the paper is to evaluate the fracture limits of a brass alloy deformed at elevated temperature under a wide range of stress states typical of hot forging process chains. A combined use of experimental and numerical techniques allowed determining the material fracture limits. Tensile and torsion tests at elevated temperature were conducted to investigate the influence that the stress triaxiality and the deviatoric parameters may have on the material formability. Numerical simulations of the above cited tests were carried out to calculate the values of the stress triaxiality factor of the tests and to correlate them with the experimentally determined strain at fracture. The CuZn40Pb2 brass alloy was taken as the reference material, being characterized by a restrict forgeability window in current hot forging processes. The obtained results state that the material deformation at fracture is greatly influenced not only by the forging temperature (allowing the determination of the lower temperature limit of the forgeability window), but also by the stress triaxiality and deviatoric parameters, meaning that a general fracture law should be dependent on these stress parameters, besides on the temperature.