Qingshuang Sui: School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China. suiqingshuang@163.com.
Jun He: School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China. hejun19861102@163.com.
Xin Zhang: School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China. zhang_xin@hebut.edu.cn.
Zhonghua Sun: HBIS Group Technology Research Institute, HBIS Group, Shijiazhuang 052165, China. sunzhonghua01@hbisco.com. ORCID
Yunfei Zhang: HBIS Group Technology Research Institute, HBIS Group, Shijiazhuang 052165, China. zhangyunfei@hbisco.com.
Yingfei Wu: HBIS Group Technology Research Institute, HBIS Group, Shijiazhuang 052165, China. wuyingfei@126.com.
Zhixiang Zhu: State Key Laboratory of Advanced Transmission Technology (Global Energy Interconnection Research Institute Co., Ltd.), Beijing 102211, China. zhuzhixiang003@163.com.
Qiang Zhang: State Key Laboratory of Advanced Transmission Technology (Global Energy Interconnection Research Institute Co., Ltd.), Beijing 102211, China. 13601210056@126.com.
Huifen Peng: School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China. peng@hebut.edu.cn.
Invar alloys with both high strength and low thermal expansion are urgently needed in fields such as overhead power transmission, aero-molds, and so on. In this paper, Cr was introduced as a cost-efficient alloying element into the Fe-36Ni binary invar alloy to increase its mechanical strength. Our results confirmed that fine CrC precipitants, together with some FeC, in the invar alloy aged at 425 °C could be obtained with a short aging time. Those precipitants then grew and aggregated at grain or sub-grain boundaries with an increase in aging time. Simultaneously, mechanical strength and coefficient of thermal expansion (CTE) parabolically varied with the increase in aging time. The sample aged at 425 °C for 7 h presented a maximum strength of 644.4 MPa, together with a minimum coefficient of thermal expansion of 3.30 × 10 K in the temperature range of 20-100 °C. This optimized result should be primarily attributed to the precipitation of the nanoscaled CrC.
