# Effect of Austenitizing on the Microstructure and Mechanical Properties of Gray Cast Iron
## 1 Introduction
As a result, the tensile strength increased by 17%. [PERSON] et al. [20] conducted an isothermal quenching heat treatment on gray cast iron at 360 \({}^{\circ}\)C for 3 h. After the heat treatment, the matrix structure consisted of acicular ferrite, high-carbon austenite, and a small amount of pearlite, and the wear weight loss was reduced by 40%. [PERSON] et al. [21] investigated the performance changes in gray cast iron under different isothermal quenching temperatures (260 \({}^{\circ}\)C-385 \({}^{\circ}\)C) and a fixed time (1 h). As the isothermal quenching temperature increased, the plasticity increased. This was because at a higher isothermal quenching temperature, the austenite content in the ausferrite structure was relatively high, which led to its coarsening. [PERSON] et al. [22] studied the influence of isothermal quenching on the microstructure and hardness of copper-containing gray cast iron. After the cast iron was subjected to an austenitizing treatment at 900 \({}^{\circ}\)C for 1 h and an isothermal quenching process at 300 \({}^{\circ}\)C for 2 h, the ausferrite morphology was acicular, the retained austenite content was 23%, and the plane-strain fracture toughness was increased by 112% compared with that of the as-cast state. [PERSON] et al. [23] studied the performance of gray cast iron under different isothermal quenching temperatures. When the quenching temperature was 400 \({}^{\circ}\)C, the comprehensive performance of the specimen reached its best, with a low wear rate and a moderate hardness. [PERSON] et al. [24] investigated the influence of different holding times on the mechanical properties of gray cast iron. The austenite content reached its maximum when the holding time increased to 90 min, and the tensile strength was increased by 10 MPa compared with that when the holding time was 30 min. Afterwards, [PERSON] et al. [25] conducted an isothermal quenching heat treatment on gray cast iron at 360 \({}^{\circ}\)C for 180 min. After the treatment, the auserrite morphology was feather-like, the tensile strength was increased by 24%, and the friction coefficient was also increased. Research by [PERSON] et al. [26] showed that when the isothermal quenching temperature was 316 \({}^{\circ}\)C and the isothermal quenching time was 60 min, the performance of gray cast iron was the best. Compared with the as-cast state, the tensile strength was doubled. Based on the aforementioned research, it is evident that alloying elements enhance the properties of gray cast iron to a certain extent by refining its microstructure. The austempering heat treatment process improves the mechanical properties of gray cast iron through the formation of an auserrite structure, which consists of aicular ferrite and high-carbon austenite. This process not only enables the material to achieve higher strength and hardness but also offers broader flexibility in property regulation. Current research on austempering heat treatment primarily focuses on adjusting the austempering temperature and duration, with limited attention being paid to the austenitizing temperature. Theoretically, regulating the austenitizing temperature can modify the auserrite content in gray cast iron, thereby affecting its strength-plasticity balance. In this study, the method of controlling the austenitizing temperature was adopted to conduct austempering treatment on gray cast iron. The influence of the austenitizing temperature on the material's microstructure was investigated, and the correlation between microstructural evolution and wear resistance was established. Moreover, the simultaneous enhancement of wear resistance and toughness was successfully achieved.