Study on Low-Temperature Sintering Behavior of 90W-7Ni-3Fe Alloys: The Influence of Sn Addition
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JMEPEG https://doi.org/10.1007/s11665-020-05055-7
Study on Low-Temperature Sintering Behavior of 90W-7Ni-3Fe Alloys: The Influence of Sn Addition Wentan Zhu, Yunzhu Ma
, Wensheng Liu, Qingshan Cai, Yufeng Huang, and Zhongliu Wen
(Submitted March 29, 2020; in revised form July 9, 2020) In this work, we investigate low-temperature sintering behavior of the 90W-7Ni-3Fe alloy by introducing Sn. The 90W-7Ni-3Fe alloy with different Sn contents (0, 0.5, 1.0 and 1.5 wt.%) was fabricated via vacuum sintering at 1300 °C for 90 min. When 1 wt.% Sn was added, the liquidus temperature of the 90W-7Ni-3Fe alloy decreased from 1477 to 1265 °C, resulting in rapid densification (relative density increased from 77.77 to 98.59%) and an homogeneous liquid-phase sintered microstructure. Electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) observations revealed that, apart from W and the c(Ni, Fe) phase, a new Ni3Sn2 phase appeared in the matrix phase. Furthermore, we discuss in detail the formation of the Ni3Sn2 phase based on element selection theory, which can be associated with the larger atomic radius of Sn and with the negative enthalpy of mixing Sn and Ni. Excessive Sn content (1.5 wt.%) led to the increase in Ni3Sn2 phase, and this deteriorated the relative density and tensile strength of the alloy. The 90W-7Ni-3Fe alloy with the addition of 1 wt.% Sn exhibited a maximum tensile strength value (710 MPa), which was much higher than that of the 90W-7Ni-3Fe alloy that was obtained at 1300 °C. Our findings shed light on further research directions and developed a 90W-6.3Ni-2.1Fe-1Sn alloy for lowtemperature sintering. Keywords
intermetallic compound, low-temperature sintering behavior, mechanical properties, tin addition, tungsten heavy alloy
1. Introduction Tungsten heavy alloys (WHAs) are typical two-phase composites that include a near-spherical BCC-structured W phase dispersed in a ductile FCC Ni-Fe-W or Ni-Cu-W solidsolution matrix phase (Ref 1). Because of the outstanding combination of the properties (which include high mechanical properties, good wear resistance and good corrosion resistance), WHAs are widely used in national defense industries and civil industries (Ref 2). Conventional WHAs are usually fabricated via liquid-phase sintering (LPS) within the temperature range of 1450–1550 C, and the obtained W grain size is generally about 40–50 lm (Ref 3, 4). In recent years, low-temperature sintered WHAs have attracted continuous interests (Ref 5-8). On the one hand, low-temperature sintering restrains grain growth, and thus, refined microstructure and attractive mechanical properties can be obtained (Ref 5, 6). On the other hand, compared with conventional sintered WHAs, low-temperature sintered WHAs have the advantages of lower sintering casting, lower energy consumption and special applications (Ref 7). Wentan Zhu, Yunzhu Ma, Wensheng Liu, Qingshan Cai, and Yufeng Huang, National Key Laboratory of Science and Technology for National Defence on High–Strength Structural Materials, Central South
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