Enhancing the Mechanical Performance of Dual-Phase Steel Through Multi-Axis Compression and Inter-Critical Annealing

TL;DR

This paper shows how processing steel with multi-axis compression and inter-critical annealing improves its strength and wear resistance, making it suitable for automotive use.

Contribution

The novel contribution is demonstrating how MAC and inter-critical annealing refine steel microstructure to enhance mechanical performance.

Findings

Multi-axis compression reduced grain size from 66 μm to 18 μm after nine passes.

Hardness and tensile strength increased significantly due to grain refinement and strain hardening.

DP steel showed better wear resistance than annealed steel, though DP9 had slightly lower resistance than DP0.

Abstract

This study examines the microstructural evolution, mechanical properties, and wear behavior of medium-carbon dual-phase steel (AISI 1040) processed via Multi-Axis Compression (MAC). The DP steel was produced through inter-critical annealing at 745 °C, followed by MAC at 500 °C, resulting in a refined grain microstructure. Optical micrographs confirmed the presence of ferrite and martensite phases after annealing, with significant grain refinement observed following MAC. The average grain size decreased from 66 ± 4 μm to 18 ± 1 μm after nine MAC passes. Mechanical testing revealed substantial improvements in hardness (from 145 ± 9 HV to 298 ± 18 HV) and ultimate tensile strength (from 557 ± 33 MPa to 738 ± 44 MPa), attributed to strain hardening and the Hall–Petch effect. Fractographic analysis revealed a ductile failure mode in the annealed sample, while DP0 and DP9 exhibited a mixed fracture mode. Both DP0 and DP9 samples demonstrated superior wear resistance compared to the annealed sample. However, the DP9 sample exhibited slightly lower wear resistance than DP0, likely due to the fragmentation of martensite induced by high accumulated strain, which could act as crack initiation sites during sliding wear. Furthermore, wear resistance was significantly enhanced due to the combined effects of the DP structure and Severe Plastic Deformation (SPD). These findings highlight the potential of MAC processing for developing high-performance steels suitable for lightweight automotive applications.

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