Thermal expansion of AlSi6Cu4/graphite composite containing 12% of synthetic graphite particles
Marian Mitko Politechnika Częstochowska, Katedra Odlewnictwa, al. Armii Krajowej 19, 42-200 Częstochowa
Annals 3 No. 8, 2003 pages 375-379
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abstract The work presents the results of dilatometric examination of the AlSi6Cu4/graphite composite obtained by squeeze casting of the mixed matrix alloy and syntethic graphite particles. The composite has been subjected to double cycle of heating from ambient temperature to the temperature of 415°C and subsequent cooling. The obtained thermal expansion curves are presented in Figures 1 and 2. Initial structure of composite and the structures after thermal cycles are shown in Figure 3. Elongation of samples by 0.11÷0.14% after the first cycle of dilatometric examination confirms the exististence of a good joining between graphite and matrix. Values of instantaneous and average coefficients of thermal expansion (αT and α25−T) for the investigated composite are greater than the corresponding values for pure matrix alloy (Tables 1-3). The average value of the coefficient of thermal expansion in the range 25÷200°C is equal 24÷25 • 10−6 1/K and is by 20% greater as compared with the matrix alloy. In the case of the weak joint at the interface the influence of graphite particles on the thermal expansion would be significantly less. Key words: aluminium alloys, composites, graphite particles, thermal expansion