FIZIKA A 8 (1999) 3 , 173-182

TEMPERATURE DEPENDENCE OF MICROSTRUCTURE IN Zn-Al ALLOYS

STANKO POPOVIĆ^a, BISERKA GRŽETA^b, BRANKO HANŽEK^c
and SNJEŽANA HAJSTER^a

^aPhysics Department, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10001 Zagreb, Croatia

^cMinistry of Education, Trg burze 6, 10000 Zagreb, Croatia

Dedicated to Professor Boran Leontić on the occasion of his 70^th birthday

Received 10 December 1999; Accepted 28 February 2000

The temperature dependence of microstructure in Zn-Al alloys, transferred to the equilibrium state by quenching from the solid solution temperature, T_SS, to room temperature (RT) and prolonged ageing at RT, was studied in situ by X-ray powder diffraction. Instead of the phase transitions expected according to the phase diagram, namely  a(M/b) + b® a' + a(M/a') ® a_SS  for the alloy with 54 at% Zn and a(M/b) + b® a'+b® a_SS  for the alloy with 62 at% Zn, the following sequence was observed for both alloys: a(M/b) + b® a' + b+ a(M/a', b) ® a'+b® a_SS. In the cooling run, a temperature hysteresis in reversal phase transitions was observed. During a repeated heating, the microstructure depended on the previous thermal treatment of the alloys.

PACS numbers: 61.50.-f, 64.70, 64.75.-p, 64.75.+g, 65.70.+y
UDC 548.73

Keywords: Zn-Al alloys, solid solution, phase transition, phase diagram, X-ray powder diffraction

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