1. Objectives: Optimal design of industrial Q&P processing parameters and suitable alloy composition to achieve the best possible combination of strength and toughness for 3 rd Generation Advanced High Strength Steels (AHSS) Q&P: What and Why? Stuart Keeler and Pete Ulintz X. Sun, PNNL, Richland, WA QUENCH AND PARTITION STEELS

2. Final cooling Partitioning time Partitioning temperature Heating rate (QT to PT) Quenching temperature Solution treatment (IA or FA) time Alloy composition Processing Austenite 1. Austenite Stability i.Carbon content ii.Particle size 2. Austenite volume fraction Martensite 1.Volume fraction 2.Different generations (and distribution 3.Nature of martensite (plate or lath) 4.Dislocation substructure in martensite Bainite and others Bainite (mixed structure of martensite /bainite/retained austenite) Precipitation of carbides Dislocations Structure Strength Toughness Elongation Hole expansion Cost Properties Performance SYSTEMS DESIGN CHART

3. DESIGN FLOWCHART Design parameters: Alloy composition and processing conditions Austenizing temp., Quench, Partition temperature/time, Heating rate ThermoCalc C γ at PT DICTRA Time at PT Olson-Cohen model Ms σ from Cγ Microstructural characterization: γ size, comp, phase fractions Instruments: SEM, TEM, 3D Atom Probe, XRD and Dilatometer Mechanical behavior: Yield stress, elongation and Ms σ temp. Tensile testing, Bolling-Richman test for Ms σ New Design Cγ from required Ms σ

4. 10  m SEM micrographs MICROSTRUCTURAL CHARACTERIZATION

5. Bolling-Richman single specimen technique Ms σ =150 o C, too high for optimum ductility Cγ (XRD) = 0.99 wt% Olson G.B., Cohen M., J. Less-Common Metals, 28 (1972) MECHANICAL BEHAVIOR

6. 0.043 C in austenite Time = 1, 15, 75, 175, 500 secs Martensite Austenite 75s 15s 1s α'α' γ 0.4µm 0.2µm THERMODYNAMIC MODELING