an ultrafine grained dual phase (ufg dp) steel containing niobium was produced by a new routeutilizing simple cold-rolling and subsequent intercritical annealing of ferrite/martensite duplex startingstructures. the effects of intercritical holding time on the microstructural evolutions and mechanicalproperties were studied. the results showed that increasing intercritical holding time enhnaced ...

A dual-phase steel chemistry has been processed with varying intercritical annealing temperatures and the properties investigated. It was found that increasing temperature in region led to an increase volume fraction (52%–65%) grain size (1.8–3.3 µm) of martensite whilst ferrite decreased. The highest tensile strengths were at low temperatures, achieving 935 MPa elongation values 21% achieved t...

Abstract In this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed quenching. Decreasing the IHT temperature from to leads to: (i) a decrease in volume fraction of austenite (martensite after quenching) 0.68 0.36; (ii) ~ 100 martensite start (Ms), mainly due higher carbon content its smaller gr...

The TA1 welded joints with different heat inputs were obtained by a fiber laser and their microstructure, mechanical properties corrosion resistance in simulated saliva solution studied. results show that the microstructure fusion zone (FZ) is needle-like ?? martensite lath-shape martensite, of heat-affected (HAZ) zigzag ? phase. With increase input, volume fraction decrease coarsened FZ, but t...

A finite element model coupled with a thermokinetic model is developed to predict the phase transformation of the laser deposition of AISI 4140 on a substrate with the same material. Four different deposition patterns, long-bead, short-bead, spiral-in, and spiral-out, are used to cover a similar area. Using a finite element model, the temperature history of the laser powder deposition (LPD) pro...

The effects of partial replacement Si by Al on the microstructure, tensile properties, and Charpy impact toughness were investigated using 0.2%C-Si/Al-Mn-Cr-B TRIP-aided martensitic steels to promote application galvanized third-generation ultrahigh- high-strength steels. was related microstructural mechanical properties. decreased volume fraction retained austenite increased stability, accompa...

We present a mathematical model for the laser surface hardening of steel. It consists of a nonlinear heat equation coupled with a system of ve ordinary diierential equations to describe the volume fractions of the occuring phases. Existence, regularity and stability results are discussed. Since the resulting hardness can be estimated by the volume fraction of martens-ite, we formulate the probl...