Microstructure and Mechanical Properties of Dual‐Phase Steels by Combining Adjusted Initial Microstructures and Severe Plastic Deformation

Abstract

Herein, the effects of initial microstructure in combination with the severe plastic deformation on the developed microstructures and mechanical properties of dual‐phase (DP) steels are investigated. DP steels are produced by an intercritical annealing from the preliminarily heat‐treated samples with different initial microstructures. The constrained groove pressing (CGP) process is additionally applied before the final intercritical annealing step. It is found that the martensitic and tempered martensitic microstructures lead to DP steels with a good balance of strength and elongation because of finer and more uniformly dispersed martensitic islands. The ferrite/pearlite banded initial microstructure is not a proper choice for intercritical annealing as all mechanical properties become worse. The CGP can be employed before intercritical annealing for refining microstructure and enhancing damage tolerance of DP steels. Nevertheless, the impacts of the CGP process on the resulted strength of DP steels are obviously different depending on the initial microstructures. The amounts, sizes, and distributions of dimples and cleavage facets on the fracture surfaces of DP steels correlate well with the corresponding microstructures and tensile characteristics.

Role of Ni Content on Microstructure, Mechanical Property, and In‐Site Local Corrosion Behavior of Welded Joints Produced by Laser Welding of Dual‐Phase Steel

“…Developing lightweight automobiles is considered promising in reducing fuel consumption and CO 2 emission. [1,2] Dual-phase (DP) steel is a widely used low-alloy steel with the advantages of high strength, superior work-hardening rate, excellent formability, and low price, [3,4] allowing it to bear the tremendous amount of energy generated from impacts. The microstructure of DP steel consists of hard martensite and a soft ferrite matrix, where the martensite is inserted into the ferrite.…”