Influence of Al contents on tensile properties and bendability of quenching and partitioning (Q&P) processed steel

Abstract

Quenching and partitioning (Q&P) process is one of the most promising processes for manufacturing AHSS that utilizes retained austenite. After evolution of primary martensite in the quenching process, the remaining austenite is chemically stabilized by carbon enrichment through carbon migration from the 'P in the partitioning process. Securing retained austenite in the Q&P steel is important for achieving excellent mechanical properties but it is often hindered by the precipitation of cementite during the partitioning process. Therefore, it is general practice to add Si or Al to suppress cementite precipitation. Unlike Si, Al does not significantly degrade weldability and galvanability, leading to various studies exploring the substitution of Si with Al in several AHSS. While there have been many studies to understand the influence of Al on the tensile properties in the Q&P processed steels, the effect of Al on the bendability, a representative parameter related to various forming processes, has not been sufficiently investigated so far. Therefore, the present study attempted to examine the influence of Al addition on the bendability as well as tensile properties in the Q&P processed medium carbon steel. Correlation between ductility and bendability was observed, and Al addition improved these properties above specific quenching temperature. Detailed analysis results will be discussed in terms of the relationship between microstructure, tensile properties, and bendability.