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A new experimental phase diagram investigation of Cu-Sb.

Fürtauer S, Flandorfer H - Monatsh. Chem. (2012)

Bottom Line: Generally, the structural descriptions of the various binary phases given in the literature were verified.The range of homogeneity of the ε phase (Cu3Ti type) was found to be higher on the Sb-rich side.Most of the reaction temperatures were verified, but a few had to be revised, such as the eutectoid reaction [Formula: see text] at 440 °C (found to occur at 427 °C in this work) and the eutectoid reaction [Formula: see text] at 400 °C (found to occur at 440 °C in this work).

View Article: PubMed Central - PubMed

Affiliation: Department of Inorganic Chemistry/Materials Chemistry, University of Vienna, Währingerstraße 42, 1090 Vienna, Austria.

ABSTRACT

Abstract: The binary system Cu-Sb is a constituent system that is studied in investigations of technically important ternary and quaternary alloy systems (e.g., casting alloys and lead-free solders). Although this binary system has been thoroughly investigated over the last century, there are still some uncertainties regarding its high-temperature phases. Thus, parts of its phase diagram have been drawn with dashed lines in reviews published in the literature. The aim of this work was to resolve these uncertainties in the current phase diagram of Cu-Sb by performing XRD, SEM-EDX, EPMA, and DTA. The results from thermal analysis agreed well with those given in the literature, although some modifications due to the invariant reaction temperatures were necessary. In particular, reactions located on the Cu-rich side of the nonquenchable high-temperature β phase (BiF3-type) left considerable scope for interpretation. Generally, the structural descriptions of the various binary phases given in the literature were verified. The range of homogeneity of the ε phase (Cu3Ti type) was found to be higher on the Sb-rich side. Most of the reaction temperatures were verified, but a few had to be revised, such as the eutectoid reaction [Formula: see text] at 440 °C (found to occur at 427 °C in this work) and the eutectoid reaction [Formula: see text] at 400 °C (found to occur at 440 °C in this work). Further phase transformations that had previously only been estimated were confirmed, and their characteristic temperatures were determined.

No MeSH data available.


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DTA curves of samples with 10–40 at% Sb
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Fig2: DTA curves of samples with 10–40 at% Sb

Mentions: The samples used for DTA measurements were annealed for four weeks at 340 °C or six months at 170 °C and quenched in cold water. The temperature program included two heating and cooling loops, starting from the annealing temperature and ending 50–100 °C above the estimated liquidus temperature. The heating rate was 5 K/min, the measured temperatures are summarized in Table 3, the DTA curves can be found in Fig. 2, and the corresponding invariant reactions are listed in Table 4. In addition, we generally performed measurements with heating rates of 10 K/min in order to observe the influence of the heating rate on the characteristic temperatures. There was no significant change in the transition temperatures when the heating rate was increased. The temperatures of the maxima of the melting peaks of all samples are consistent with the liquidus temperatures given in [3]. The solidus of the β phase, which was established by performing DTA measurements of five samples with 21–28 at% Sb, was also in agreement with the literature [3]. The reaction temperature as well as the liquidus concentration of 19 at% Sb for the eutectic reaction located at 645 °C () were confirmed based on three of our samples; see Table 3. However, samples at 10, 17.5, and 19.5 at% Sb showed some discrepancies from the data in the literature at temperatures below 645 °C [3]. Strong effects were observed in all three samples at temperatures of 467 and 484 °C. We allocated the effect at 467 °C to the reaction , which is described in the literature as occurring at 462 °C [3], and the effect at 484 °C to (which takes place at 488 °C according to the literature [3]). However, according to the phase relations [3], the effect at 467 °C should not be observable in the sample with 10 at% Sb in the first heating run. Surprisingly, this effect was even stronger in the second heating run. In order to clarify this discrepancy, we annealed this sample at 470 and 480 °C for 28 days. Both temperatures resulted in large amounts of (Cu) and γ, but also traces of the β phase (see Tables 5, 6). It is worth noting at this point that the β phase cannot be quenched; it mainly decomposes to the low-temperature phases δ and ε. Thus, we instead assume that (Cu) is in equilibrium with γ at both temperatures. Although the effect is clearly present at 467 °C in the sample with 10 at% Sb, we have decided not to change the previously accepted phase diagram given in the literature [3]. XRD analysis of Cu90Sb10 annealed at 435 °C and Cu82.5Sb17.5 annealed at 430 °C showed (Cu) and δ as equilibrium phases (see Fig. 3). According to the literature, these samples should both contain the γ phase [3]. Supported by an invariant reaction observed at 440 °C during DTA of Cu82.5Sb17.5, we fixed the eutectoid reaction at this temperature. This is additionally supported by the fact that the original source of the reaction temperature of 400 °C given in [3] could not be found and thus appears to be estimated. The peritectoid reaction was corroborated by DTA of samples with 21 and 22.5 at% Sb. However, the corresponding temperature (440 °C) differs slightly from the literature value (445 °C [3]). DTA of these samples should also show invariant reactions according to (390 °C) and (360 °C), and we did indeed find the reaction at 360 °C in Cu87.5Sb22.5 as a weak effect in the second heating run. However, we could not locate the peritectoid reaction at 390 °C. Thermal analysis of the samples with 24 and 26 at% Sb agreed well with the previously reported phase diagram [3] above 350 °C. On the other hand, DTA of samples annealed at 170 °C did not indicate the invariant reaction at 260 °C . Instead, we found two further signals at different temperatures that are possibly related to this reaction (24 at% Sb 323 °C, 26 at% Sb 302 °C; see also Table 3). Because XRD data for the samples with 21, 22.5, 24, and 26 at% Sb are consistent with the literature data [3], we kept the previously reported phase relations and reaction temperatures. Using the samples with 28 and 30 at% Sb, we were able to determine the temperature of the eutectoid reaction as 427 °C, which had previously been estimated as 440 °C ([3]: dashed lines, see Fig. 1). The liquidus and solidus curves allowed us to estimate the congruent melting point of the β phase at 690 °C and 29 at% Sb ([3], 683 °C). Finally, we also verified the eutectic reaction at 526 °C () and the peritectic reaction at 586 °C ().


A new experimental phase diagram investigation of Cu-Sb.

Fürtauer S, Flandorfer H - Monatsh. Chem. (2012)

DTA curves of samples with 10–40 at% Sb
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4495028&req=5

Fig2: DTA curves of samples with 10–40 at% Sb
Mentions: The samples used for DTA measurements were annealed for four weeks at 340 °C or six months at 170 °C and quenched in cold water. The temperature program included two heating and cooling loops, starting from the annealing temperature and ending 50–100 °C above the estimated liquidus temperature. The heating rate was 5 K/min, the measured temperatures are summarized in Table 3, the DTA curves can be found in Fig. 2, and the corresponding invariant reactions are listed in Table 4. In addition, we generally performed measurements with heating rates of 10 K/min in order to observe the influence of the heating rate on the characteristic temperatures. There was no significant change in the transition temperatures when the heating rate was increased. The temperatures of the maxima of the melting peaks of all samples are consistent with the liquidus temperatures given in [3]. The solidus of the β phase, which was established by performing DTA measurements of five samples with 21–28 at% Sb, was also in agreement with the literature [3]. The reaction temperature as well as the liquidus concentration of 19 at% Sb for the eutectic reaction located at 645 °C () were confirmed based on three of our samples; see Table 3. However, samples at 10, 17.5, and 19.5 at% Sb showed some discrepancies from the data in the literature at temperatures below 645 °C [3]. Strong effects were observed in all three samples at temperatures of 467 and 484 °C. We allocated the effect at 467 °C to the reaction , which is described in the literature as occurring at 462 °C [3], and the effect at 484 °C to (which takes place at 488 °C according to the literature [3]). However, according to the phase relations [3], the effect at 467 °C should not be observable in the sample with 10 at% Sb in the first heating run. Surprisingly, this effect was even stronger in the second heating run. In order to clarify this discrepancy, we annealed this sample at 470 and 480 °C for 28 days. Both temperatures resulted in large amounts of (Cu) and γ, but also traces of the β phase (see Tables 5, 6). It is worth noting at this point that the β phase cannot be quenched; it mainly decomposes to the low-temperature phases δ and ε. Thus, we instead assume that (Cu) is in equilibrium with γ at both temperatures. Although the effect is clearly present at 467 °C in the sample with 10 at% Sb, we have decided not to change the previously accepted phase diagram given in the literature [3]. XRD analysis of Cu90Sb10 annealed at 435 °C and Cu82.5Sb17.5 annealed at 430 °C showed (Cu) and δ as equilibrium phases (see Fig. 3). According to the literature, these samples should both contain the γ phase [3]. Supported by an invariant reaction observed at 440 °C during DTA of Cu82.5Sb17.5, we fixed the eutectoid reaction at this temperature. This is additionally supported by the fact that the original source of the reaction temperature of 400 °C given in [3] could not be found and thus appears to be estimated. The peritectoid reaction was corroborated by DTA of samples with 21 and 22.5 at% Sb. However, the corresponding temperature (440 °C) differs slightly from the literature value (445 °C [3]). DTA of these samples should also show invariant reactions according to (390 °C) and (360 °C), and we did indeed find the reaction at 360 °C in Cu87.5Sb22.5 as a weak effect in the second heating run. However, we could not locate the peritectoid reaction at 390 °C. Thermal analysis of the samples with 24 and 26 at% Sb agreed well with the previously reported phase diagram [3] above 350 °C. On the other hand, DTA of samples annealed at 170 °C did not indicate the invariant reaction at 260 °C . Instead, we found two further signals at different temperatures that are possibly related to this reaction (24 at% Sb 323 °C, 26 at% Sb 302 °C; see also Table 3). Because XRD data for the samples with 21, 22.5, 24, and 26 at% Sb are consistent with the literature data [3], we kept the previously reported phase relations and reaction temperatures. Using the samples with 28 and 30 at% Sb, we were able to determine the temperature of the eutectoid reaction as 427 °C, which had previously been estimated as 440 °C ([3]: dashed lines, see Fig. 1). The liquidus and solidus curves allowed us to estimate the congruent melting point of the β phase at 690 °C and 29 at% Sb ([3], 683 °C). Finally, we also verified the eutectic reaction at 526 °C () and the peritectic reaction at 586 °C ().

Bottom Line: Generally, the structural descriptions of the various binary phases given in the literature were verified.The range of homogeneity of the ε phase (Cu3Ti type) was found to be higher on the Sb-rich side.Most of the reaction temperatures were verified, but a few had to be revised, such as the eutectoid reaction [Formula: see text] at 440 °C (found to occur at 427 °C in this work) and the eutectoid reaction [Formula: see text] at 400 °C (found to occur at 440 °C in this work).

View Article: PubMed Central - PubMed

Affiliation: Department of Inorganic Chemistry/Materials Chemistry, University of Vienna, Währingerstraße 42, 1090 Vienna, Austria.

ABSTRACT

Abstract: The binary system Cu-Sb is a constituent system that is studied in investigations of technically important ternary and quaternary alloy systems (e.g., casting alloys and lead-free solders). Although this binary system has been thoroughly investigated over the last century, there are still some uncertainties regarding its high-temperature phases. Thus, parts of its phase diagram have been drawn with dashed lines in reviews published in the literature. The aim of this work was to resolve these uncertainties in the current phase diagram of Cu-Sb by performing XRD, SEM-EDX, EPMA, and DTA. The results from thermal analysis agreed well with those given in the literature, although some modifications due to the invariant reaction temperatures were necessary. In particular, reactions located on the Cu-rich side of the nonquenchable high-temperature β phase (BiF3-type) left considerable scope for interpretation. Generally, the structural descriptions of the various binary phases given in the literature were verified. The range of homogeneity of the ε phase (Cu3Ti type) was found to be higher on the Sb-rich side. Most of the reaction temperatures were verified, but a few had to be revised, such as the eutectoid reaction [Formula: see text] at 440 °C (found to occur at 427 °C in this work) and the eutectoid reaction [Formula: see text] at 400 °C (found to occur at 440 °C in this work). Further phase transformations that had previously only been estimated were confirmed, and their characteristic temperatures were determined.

No MeSH data available.


Related in: MedlinePlus