Calorimetric Measurements of Liquid Al-Zn Alloys
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INTRODUCTION
THE Zn-containing aluminum alloys have a good castability and a low casting shrinkage. Furthermore, the addition of zinc increases the mechanical properties as well as improves the weldability and the corrosion resistance. Therefore, these alloys are used in the automotive industry, among others, on panels or fans. The Al-Zn alloys are interesting extensively for the aerospace industry because of their abilities to withstand high pressure and stress during flights at high altitude and considerable speeds.[1–4] At present, the Al-Znbased alloys are of great interest because of their good damping properties as well as a considerably lower density as compared to the conventional cast iron. The Al-Zn system has been investigated extensively by many researchers. The solidus and liquidus curves were studied by References 5 through 17 with the use of the thermal analysis. The activity of Al in the Al-Zn liquid alloys was measured with the use of the EMF method by Batalin and Beloborodova[18] at 960 K (687 C), Predel and Schallner[19] at 1000 K and 1100 K (727 C and 827 C), and Sebkova and Beranek[20] at 973 K and 1073 K (700 C and 800 C). Their results agree fairly well with each other. The activity of Zn in the Al-Zn liquid alloys was determined by means of the isopiestic method by Bolsaitis and Sullivan[21] at 1076 K (803 C), with the use of the dew point method by Lutz and Voigt[22] at 950 K and 1050 K (677 C and 777 C) and Yazawa and Lee[23] at 1073 K (800 C), with the use of the EMF method by Eremenko[24] at 960 K (687 C) and 1120 K ADAM DE ˛ BSKI, Assistant Professor, and WŁADYSŁAW GA ˛ SIOR, Professor, are with the Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 30-059 Krako´w, 25, Reymonta Street, Poland. Contact e-mail: [email protected] KATARZYNA SZMIT, Student, is with AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Krako´w, Poland. Manuscript submitted May 7, 2015. Article published online July 20, 2016 METALLURGICAL AND MATERIALS TRANSACTIONS A
(847 C), and with the use of the X-ray method by Schneider and Stoll[25] at 923 K and 1073 K (650 C and 800 C). The mixing enthalpy of the liquid Al-Zn alloys was performed calorimetrically by Wittig and Keil[26] at 953 K and 973 K (680 C and 700 C). Connell and Downie[27] determined the enthalpies of formation of the fcc alloys at 599 K, 637 K, and 648 K (326 C, 364 C, and 375 C). In 1987, Shaarbaf et al.[28] used differential scanning calorimetry (DSC) to measure the enthalpy change associated with the dissociation of a 29.5 at.pct Zn alloy into Al (fcc) and Zn (hcp) phases. Their results agree with the research of Wittig and Scho¨ffl[29] and the data of Lyashenko,[30] but there is a significant discrepancy between them as well as the results of several EMF studies[31–36] of solid alloys. In 2014, Balanovic´ et al.,[37] on the basis of the Olsen calorimetric method, determined the thermodynamic properties (activities, activity coefficients, partial, and integral excess Gibbs energy and mixing ener
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