Reducing the Uncertainty in Flow Forming of Metastable Austenites

<jats:p>Flow forming of metastable austenites is an innovative, incremental metal forming process with special capabilities due to the TRIP effect. However, the TRIP effect during flow forming is significantly affected by disturbances and especially batch fluctuations leading to process uncertainty. This aspect is further analyzed and quantified in this paper to give insights on how to minimize the impact of uncertainty. For this purpose, semifinished parts and resulting flow forming workpieces are systemically characterized concerning their properties and the property uncertainty supported by mathematical methods like correlation analysis and error propagation. A result is that the most influencing impact factor on the strain induced α’-martensite volume fraction as a material property are batch fluctuations, specifically the variations of the chemical composition. Those especially appear from batch to batch, but also within a batch accompanied by e.g. temperature effects. To counter this challenge, different methods from control theory like closed-loop property control and adaptive control can be applied to flow forming. Thus, uncertainty will be reduced to increase process robustness and to enable industrial exploitation of the TRIP effect in flow forming of metastable austenitic steels.</jats:p>