| METALS AND METAL MATRIX COMPOSITES |
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| Effect of Chemical Composition and Aging Treatment on Properties of Ni-Cr-Al-Fe Precise Resistance Alloy |
| WANG Yong1, YANG Xianjun2, YU Wenxin2, HUANG Shudong1, XU Yonghong2, WU Da2, QIAO Liying1
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1 College of Materials Science & Engineering, Chongqing University, Chongqing 400045
2 Chongqing Chuanyi Metallic Functional Materials Co., Ltd., Chongqing 400702 |
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Abstract Nickel-chromium based precise resistance alloys, including primarily Ni-Cr-Al-Fe and Ni-Cr-Al-Cu alloys, are developed from the electrothermal alloy Ni80Cr20 by adding some other alloy elements. Because of their excellent electrical properties, such as high resistivity, low temperature coefficient of resistivity (TCR) and copper thermoelectric potential, these alloys are the key of high-performance resistance elements and attract much attention. However, fundamental researches on the precise resistance alloys are seldom reported, restricting the development of the manufacturing technology of these alloys.
In this paper, a series of alloys with different compositions were designed and manufactured so as to investigate the effects of the concentration of Al and Fe, which were the main alloying elements in Ni-Cr-Al-Fe precise resistance alloy on the mechanical and electrical properties. Also, solid solution and aging treatment processes were conducted in order to explore the influence of heat treatment on the properties because the preci-sion resistance alloys were usually used after aging treatment. Grain sizes, hardness and tensile properties of different alloys were measured. The electrical properties of alloy were tested by using resistance tester, TCR tester and thermocouple calibration furnace respectively. It was found that the grain size decreased with the increase of Al but it was not sensitive to the content of Fe, in the concentration range of this work. As for the mechanical properties, the strength and hardness of the alloy increased with the increase of Al and Fe content, and the plasticity decreased correspondingly. But the effect of Fe was much less than Al. After aging treatment, the strength and hardness increased simultaneously, but the plasticity almost had no change. In terms of electrical properties, as the Al and Fe content increased, the resistivity increased too. These two elements affected the TCR conversely, i. e., the TCR declined with the increase of Al but rose with the increase of Fe. Furthermore, negative TCR values were attained under some conditions. Hence, it was expectable to get TCR values close to zero by adjusting the ratio of Al and Fe properly. With the increase of Al content, the copper thermoelectric potential decreased first and then increased, and the minimum appeared at 3.2wt%—3.7wt% Al. However, it was not sensitive to Fe content. Aging treatment affected the electric properties favorably, that is, it increased the resistivity but decreased TCR and copper thermoelectric potential. Generally, the content of Al affected the electrical and mechanical properties obviously, while the primary effect of Fe content was on TCR.
In this paper, the mechanism of the evolution of mechanical and electrical properties of precise resistance alloys with composition and heat treatment was discussed from the aspect of grain size, microstructure variation during heat treatment and extranuclear electron distribution of different elements. These results was hopeful to provide some practical references for the optimization of the composition, process and performance of Ni-Cr-Al-Fe precise resistance alloy.
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Published: 28 October 2019
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| Fund:This work was financially supported by the National Key R & D Program of China ( 2016YFB0402603). |
| About author:: Yong Wang, born in February 1968, Ph.D., postdoctoral fellow, is an associate professor at the School of Materials Science and Engineering, Chongqing University, and a member of the National Electrotechnical Alloy Standardization Technical Committee. He has long been engaged in teaching and research work in electrical alloys, biomedical metal materials, phase change theory and powder metallurgy. He has participated in the research of various vertical research projects and various horizontal scientific research projects of the Ministry of Scie-nce and Technology, the Natural Science Foundation, and the Chongqing Science and Technology Bureau. He is currently undertaking the “13th and 5th” National Key R&D Program (2016YFB0402600) and the Research Work of the City’s Technical Innovation and Application Demonstration Special Industry Key Research and Development Project of Chongqing (cstc2018jszx-cyzdX0090). He won 2 provincial and ministerial science and technology second prizes, 1 third prize, more than 70 academic papers, and more than 10 invention patents. |
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2019, Vol. 33 
