Effect of Carbon Partitioning, Carbide Precipitation, and Grain Size on Brittle Fracture of Ultra-High-Strength, Low-Carbon Steel after Welding by a Quenching and Partitioning Process

Metals

Esa Vuorinen¹  Farnoosh Forouzan¹  Frank Mücklich²  M.Agustina Guitar² 

[1] Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-97187 Luleå, Sweden;Department of Materials Science, Functional Materials, Saarland University, D-66041 Saarbrücken, Germany;

关键词: low-carbon AHSS;    Q&;    P;    toughness;    modelling;    precipitation;    martensite packet;   

DOI  :  10.3390/met8100747

来源: DOAJ

【 摘 要 】

To improve the weld zone properties of Advanced High Strength Steel (AHSS), quenching and partitioning (Q&P) has been used immediately after laser welding of a low-carbon steel. However, the mechanical properties can be affected for several reasons: (i) The carbon content and amount of retained austenite, bainite, and fresh martensite; (ii) Precipitate size and distribution; (iii) Grain size. In this work, carbon movements during the partitioning stage and prediction of Ti (C, N), and MoC precipitation at different partitioning temperatures have been simulated by using Thermocalc, Dictra, and TC-PRISMA. Verification and comparison of the experimental results were performed by optical microscopy, X-ray diffraction (XRD), Scanning Electron Microscop (SEM), and Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive Spectroscopy (EDS) and Electron Backscatter Scanning Diffraction (EBSD) analysis were used to investigate the effect of martensitic/bainitic packet size. Results show that the increase in the number density of small precipitates in the sample partitioned at 640 °C compensates for the increase in crystallographic packets size. The strength and ductility values are kept at a high level, but the impact toughness will decrease considerably.

【 授权许可】

Unknown