Prüfung der mechanischen Eigenschaften von “Quenching und Partitioning”‐Gefügen mit berührungsloser Dehnungsmessung

The “Quenching and Partitioning” (“Q&P”) concept was designed to fill the gap between the first and second generation of Advanced High Strength Steels (AHSS). It aims at a multiphase microstructure of retained austenite in a matrix of carbon depleted martensite. The martensitic components enhance the strength properties. The ductility is improved by the TRIP effect. This work investigates the “quenching and partitioning” response of a nickel and silicium alloyed TRIP steel. After “quenching and partitioning” processing the mechanical properties are evaluated by tensile testing. An adapted specimen geometry and the contact free measurement of the elongation by a laser speckle system are used. The mechanical properties of the “quenching and partitioning” microstructure are compared to the fully martensitic state and reviewed with respect to published data. Additional tests are stopped after a well defined plastic deformation. Subsequently the retained austenite fraction is measured magnetically in the test length. As a result the TRIP effect can be evaluated. The “quenching and partitioning” processing leads to tensile strengths of around 1300 MPa at elongations of more than 10 %. The martensitic microstructure exhibits a higher tensile strength and lower elongation values. The decreasing fraction of retained austenite with plastic deformation implies the TRIP effect. Comparable mechanical properties are reported in the published literature. The proposed method of annealing and adapted testing shows effective for the investigation of sophisticated heat treatment procedures.