چكيده لاتين :
Til rmal f atigue is a stochas tic process often showing considerable scatter e~י(יn in
controlled en ironments. Due to complexity 0/ thermal fatigue, there is no a complete analytical
solution tor p redicting the effect 0/ this property on the life 0/ various comp onents, subjected to
severe thermal fluct uations. Among these components, one can mention car cylinder; cylinder head
and piston which bear damages due to thermal fa tigue. All these components are usually produced
b י casting technique " I II order to comprehend and compare the thermal fa tigue res l: lance of cast
AI alloys 356 atu] 413, this research was designed and performed. For this pu rp ose, s veral
samples 111 the fo rm ofdisc were cast from the two alloys in sand mould. The -microstructures ofthe
cast samples were studied by light microscopy in order to choose the samp les with the least
amounts of defects f or thermal fa tigue tests. The results 0/ thermal fa tigue tests showed that the
nucleation ofmicrocracks in AI-356 alloy occurred at shorter time relative to those occurred in ..114J3
allov under tile same test conditions. In addition, the density 0/micro-crack in AI-356 alloy
W{1.יi more titan that 0/ AI- "lJ alloy, The results 0/froctography on 356 alloy indicated that the
cracks " יere generally nucleated from inter-dendritic shrinkage porosities and occasionullv [ram
rile illter {Ice 0/ silicon pa rticles with the matrix. The growth 0/ these micro cracks was along the
dendrite arms. Fro tography 0/413 alloy fracture surfaces showed that nucleation ofmicrocracks
I1יIlS often associated with silicon particles.
Thermal Fatigue, Inter-Dendritic Fracture, Silicon Particles, Al-Allov, Microcracks, Al
356, AI 413
