Parameters controlling the performance of AA319-type alloys Part II. Impact properties and fractography

摘要: Abstract The Charpy impact energy of Al–Si–Cu AA319-type alloys was measured in terms the total absorbed energy. specimens were machined from end-chilled castings to incorporate effect cooling rate on properties. Unnotched used increase accuracy measurements, and emphasize microstructure. influence microconstituents strength investigated by adding various alloying elements (i.e. Sr, Fe, P) AA319 base alloy, applying two different heat treatments (T5, T6). results show that strontium-modification enhances properties, so Sr-modified alloy exhibits highest properties compared base, other at any given dendrite arm spacing (DAS). increases with rate, while iron, phosphorus additions have a detrimental due, respectively, formation β-Al5FeSi, oxide particles during solidification. T6 treatment assists even distribution, dissolution (including block-like CuAl2 particles) into aluminum matrix. With more Cu available for strengthening aging, toughness is greatly enhanced. In unmodified crack initiation, propagation occur mainly through Si-particle fracture, mechanism void coalescence. Sr-modified, 1.2% Fe-containing 319 alloys, however, initiation takes place fragmentation Si, or Cu2FeAl7 particles. Crack occurs cleavage β-Fe platelets, fracture Cu-intermetallics, brittle Si Such samples exhibit very low energies.