Wear resistance and high-temperature compression strength of Fcc CuCoNiCrAl 0.5 Fe alloy with boron addition
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25/3/04
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Wear Resistance and High-Temperature Compression Strength of Fcc CuCoNiCrAl0.5Fe Alloy with Boron Addition CHIN-YOU HSU, JIEN-WEI YEH, SWE-KAI CHEN, and TAO-TSUNG SHUN This study discusses the wear resistance and high-temperature compression strength of CuCoNiCrAl0.5Fe alloy with various amounts of boron addition. Experiments show that within the atomic ratio of boron addition from x 0 to x 1.0 in CuCoNiCrAl0.5FeBx (referred to as B-0 to B-1.0 alloys), the alloys are of fcc structure with boride precipitation. The volume fraction of borides increases with increasing boron addition. The corresponding hardness increases from HV 232 to HV 736. Wear resistance and high-temperature compression strength are significantly enhanced by the formation of boride. The alloys with boride are less tough. The superior wear resistance of B-1.0 alloy, which is even better than SUJ2 wear-resistant steel, indicates that the CuCoNiCrAl0.5FeBx alloys have potential applications as ambient- and high-temperature mold, tool, and structural materials.
I. INTRODUCTION
CONVENTIONALLY, alloys have been designed to have a major element as their main component and other minor element(s) as their modified alloying component(s), such as in the cases of ferrous, aluminum, copper, titanium, and magnesium alloys. In an attempt to escape the conventional realm of alloy designing, a new alloy system was proposed in 1996 by the Alloy Research Group, National Tsing Hua University (Hsinchu, Taiwan).[1] This alloy system (also called “high-entropy alloy”[1]) contains alloys with more than five components. Each chemical constituent in the alloy system is higher than 5 at. pct and less than 35 at. pct. The overarching design idea makes each of the alloys in the system have many major components in a single alloy in order to increase the degrees of freedom. According to previous studies,[1–6] these multimajor component alloys possess the following properties: (1) ease of amorphization and nanoprecipitation in the alloy, (2) thermal stability, (3) high hardness, and (4) superior corrosion resistance. Among those previous studies, Reference 5 pointed out that fcc CuCoNiCrAl0.5Fe is ductile, work hardenable, and strong at high temperature up to 800 °C, indicating that this alloy has potential applications in high-temperature structures and working tools. Therefore, the purpose of this study is to modify this alloy to further improve its hightemperature properties. The effects of boron addition in this alloy on the wear resistance and high-temperature strength are also introduced in this study.
Fe-18.2 wt pct B master alloy was used for boron addition in the alloy. An induction furnace was used to melt the alloy in air. The compositions of the alloys are listed in Table I. The size of the ingots was 8 7 14 (cm). Specimens were cut to desired dimensions by electric arc line cutting. JEOL-5410 scanning electron microscopy (SEM) with JEOL-JXA-8800 M electron-probe microanalysis (EPMA) were used to analyze the microstructure and
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