Thermomechanical cyclic quenching and tempering (TMCT) can strengthen steels through a grain size reduction mechanism. The effect of TMCT on microstructure, mechanical, and electrochemical properties of AISI 1345 steel was investigated. Steel samples heated to 1050°C, rolled, quenched to room temperature, and subjected to various cyclic quenching and tempering heat treatments were named TMCT-1, TMCT-2, and TMCT-3 samples, respectively. Microstructure analysis revealed that microstructures of all the treated samples contained packets and blocks of well-refined lath-shaped martensite and retained austenite phases with varying grain sizes (2.8–7.9 µm). Among all the tested samples, TMCT-3 sample offered an optimum combination of properties by showing an improvement of 40% in tensile strength and reduced 34% elongation compared with the non-treated sample. Nanoindentation results were in good agreement with mechanical tests as the TMCT-3 sample exhibited a 51% improvement in indentation hardness with almost identical reduced elastic modulus compared with the non-treated sample. The electrochemical properties were analyzed in 0.1 M NaHCO₃ solution by potentiodynamic polarization and electrochemical impedance spectroscopy. As a result of TMCT, the minimum corrosion rate was 0.272 mm/a, which was twenty times less than that of the non-treated sample. The impedance results showed the barrier film mechanism, which was confirmed by the polarization results as the current density decreased.

热机械循环淬火和回火（TMCT）可以通过减小晶粒尺寸的机制来强化钢。研究了TMCT对AISI 1345钢的组织，力学和电化学性能的影响。加热至1050°C，轧制，淬火至室温并经过各种循环淬火和回火热处理的钢样品分别称为TMCT-1，TMCT-2和TMCT-3样品。显微组织分析表明，所有处理过的样品的显微组织都包含细化板条形马氏体的小包和块，并保留了晶粒尺寸（2.8-7.9 µm）不同的奥氏体相。在所有测试样品中，与未处理的样品相比，TMCT-3样品的抗张强度提高了40％，伸长率降低了34％，从而提供了最佳的性能组合。纳米压痕的结果与机械测试非常吻合，因为与未处理的样品相比，TMCT-3样品的压痕硬度提高了51％，弹性模量几乎相同。在0.1 M NaHCO中分析电化学性能₃溶液通过电位动力学极化和电化学阻抗谱分析。作为TMCT的结果，最小腐蚀速率为0.272mm / a，这是未处理样品的最小腐蚀速率的二十倍。阻抗结果显示了阻挡膜的机理，这可以通过极化结果随着电流密度的降低来证实。