Materials Science & Engineering A 793 (2020) 139751 Available online 28 June 2020 0921-5093/© 2020 Elsevier B.V. All rights reserved. Texture development during austempering process of an AISI 4130 steel O. Heidary a , O. Mirzaee a, * , A. Honarbakhsh Raouf a , E. Borhani b, ** a Faculty of Materials and Metallurgical Engineering, Semnan University, Semnan, 19111-35131, Iran b Dep. of Nanotechnology, Faculty of New Science and Technologies, Semnan University, Semnan, Iran A R T I C L E INFO Keywords: Texture development Pole fgure Austempering Steel Heat treatment Mechanical properties ABSTRACT In this investigation, microstructural development and mechanical properties of an automotive grade AISI 4130 steel were explored through various heat treatment routes. In that regard, frst of all the effect of austenitization temperature and time on the mechanical properties were assessed. Then, an optimum austenitization tempera- ture was obtained for austempering at 400 � C and for the duration of 20, 40 and 60 min. Finally, under the optimum austenitization condition, austempering temperatures from 300 � C to 500 � C, with 50 � C interval, was evaluated in terms of mechanical properties changes and microstructural development. Optical microscope (OM) and Field Emission Scanning Electron Microscope (FE-SEM) equipped with Electron backscattered diffraction (EBSD) detector were employed for microstructural studies. Tensile tests, hardness measurements and Charpy impact tests were done to defne the mechanical properties of the steels. Results show that austenitization at 900 � C for 15 min gives the highest hardness value. This was related to the development of bainite microstructure at the expense of martensite. Also, under different austenitization temperatures, austempering time of 20 min at 400 � C provides the highest strength level. As well, austempering temperature of 400 � C was determined as the best temperature to obtain optimum amount of bainite while strength and ductility levels are acceptable. {100} pole fgures for some of the austempering steps were gauged and showed a random texture for the initial steel. However, after austempering process at different temperatures and times, textured structures with the main components of Cube ({100}<001>), Copper({112}<111>), S ({123}<634>), and Brass ({110}<112>)were obtained. Texture components were substantially changed with changing the austempering temperature and time. Out of these texture components, non-cube textures were developed for the best combination of aus- tempering temperature and time. This latest fnding could explain satisfactory levels of mechanical properties under the optimum condition of heat treatment. 1. Introduction Low carbon low alloy steels used in automotive applications have undergone signifcant development over the past few decades. The main driving force for such changes was the ever tightening market re- quirements for the development of steels with superior mechanical properties specially in terms of strength and toughness [1]. Of the most important family of automotive steels used in a variety of applications such as shafts, and gear is a simple ferritic-pearlitic type of steel [2]. Process wise, most of the low alloy steels for automotive applications go through normalization and tempering processes. However, there is an increasing demand to perform quenching and tempering process as well [3]. This latest development if mainly geared towards obtaining steels with bainitic microstructure. Bainitic microstructure was initially observed by Davenport and Bain in 1920 which while investigating isothermal transformation of austenite at temperatures higher than martensite start temperature (M s ). They named the structure Martensite-Troostite since they thought that this structure forms in the same way as martensite [4]. Nevertheless, it was later identifed that such a structure is totally different than that of the martensitic microstructure and was called “Bainite”. Usually, the bainitic transformation in steels occurs in the range of temperature be- tween the end of the formation of pearlite and the M s [5]. Therefore, the kinetic of bainite transformation is a mix of diffusional pearlite as well as non-diffusional martensite [6]. Like pearlite, the transformation prod- ucts of bainite is commonly made of cementite carbides and ferrite phases [7]. Usually to achieve bainitic structure an austempering process is * Corresponding author. ** Corresponding author. E-mail addresses: o_mirzaee@semnan.ac.ir (O. Mirzaee), e.borhani@semnan.ac.ir (E. Borhani). Contents lists available at ScienceDirect Materials Science & Engineering A journal homepage: http://www.elsevier.com/locate/msea https://doi.org/10.1016/j.msea.2020.139751 Received 27 May 2020; Received in revised form 11 June 2020; Accepted 11 June 2020