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, first of all the effect of austenitization temperature and time on the mechanical properties were assessed. Then, an optimum austenitization temperature 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 define 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 figures 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 austempering temperature and time. This latest finding could explain satisfactory levels of mechanical properties under the optimum condition of heat treatment.

在这项研究中，通过各种热处理途径探索了汽车级AISI 4130钢的显微组织发展和力学性能。在这方面，首先评估了奥氏体化温度和时间对机械性能的影响。然后，获得最佳奥氏体化温度以在400°C下进行20分钟，40分钟和60分钟的回火。最后，在最佳奥氏体化条件下，从力学性能变化和微观组织发展的角度评估了从300°C到500°C（间隔50°C）的回火温度。光学显微镜（OM）和配备电子背散射衍射（EBSD）检测器的场发射扫描电子显微镜（FE-SEM）被用于微观结构研究。拉伸试验 进行了硬度测量和夏比冲击测试以定义钢的机械性能。结果表明，在900°C下奥氏体化15分钟可获得最高的硬度值。这与以马氏体为代价的贝氏体显微组织的发展有关。同样，在不同的奥氏体化温度下，在400°C下20分钟的回火时间可提供最高的强度水平。同样，将400℃的奥氏体回火温度确定为获得最佳贝氏体量的最佳温度，同时强度和延展性水平是可接受的。测量了一些奥氏体淬火步骤的{100}极图，并显示出初始钢的随机织构。但是，经过不同温度和时间的回火处理后，具有立方主要成分的纹理结构（{100} <001>），获得了铜（{112} <111>），S（{123} <634>）和黄铜（{110} <112>）。随着奥氏体化温度和时间的改变，质地成分也发生了实质性变化。在这些纹理成分中，开发了非立方体纹理以实现奥氏体温度和时间的最佳组合。这一最新发现可以解释在最佳热处理条件下令人满意的机械性能水平。