Zhao Li, Li Baichun, Tan Chaolin, Zhu Hongmei
Key Laboratory of Hunan Province of Equipment Safety Service Technology under Extreme Environment, Hengyang 421001, China.
Singapore Institute of Manufacturing Technology (SIMTech), Agency for Science, Technology and Research (A*STAR), 5 Cleantech Loop, Singapore 636732, Singapore.
Materials (Basel). 2024 Sep 21;17(18):4628. doi: 10.3390/ma17184628.
AISI 431 martensitic stainless steels (MSS) with 2.5 wt% Cu were fabricated via laser-directed energy deposition additive manufacturing followed by single-step tempering treatment. The influences of different tempering times at 600 °C on microstructure and mechanical properties of the as-deposited 431-2.5Cu MSS have been explored and analyzed. The as-deposited MSS specimen primarily consisted of lath martensite, austenite and C carbide. After the single-step tempering treatment at 600 °C, Cu-enriched (ԑ-Cu) nano-precipitates and reverse austenite can be formed and promoted by extending the tempering treatment. The microhardness, strength and elongation can be improved with increasing the tempering time up to 1.0 h, and subsequently reduced with the tempering time prolonging to 2.0 h. Compared to 431 MSS that requires a multiple-step heat treatment for excellent performance, the 431-2.5Cu MSS specimen presented superior tensile properties after single-step tempering at 600 °C for 1.0 h in the present work. The ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of one-hour tempered MSS were 1611 MPa, 1334 MPa and 16.3%, respectively. This study provides a quantitative theoretical reference and experimental basis for realizing short-process fabrication of the Cu-bearing MSS with high strength and ductility.
通过激光定向能量沉积增材制造工艺制备了含2.5 wt%铜的AISI 431马氏体不锈钢（MSS），随后进行单步回火处理。研究并分析了600℃下不同回火时间对沉积态431-2.5Cu MSS组织和力学性能的影响。沉积态MSS试样主要由板条马氏体、奥氏体和C碳化物组成。在600℃进行单步回火处理后，通过延长回火时间可形成并促进富铜（ԑ-Cu）纳米析出相和逆奥氏体。随着回火时间增加至1.0 h，显微硬度、强度和伸长率提高，随后随着回火时间延长至2.0 h而降低。与需要多步热处理才能获得优异性能的431 MSS相比，在本研究中，431-2.5Cu MSS试样在600℃单步回火1.0 h后具有优异的拉伸性能。回火1小时的MSS的抗拉强度（UTS）、屈服强度（YS）和伸长率（EL）分别为1611 MPa、1334 MPa和16.3%。本研究为实现高强度和高韧性含铜MSS的短流程制造提供了定量理论参考和实验依据。
