Structural investigations of Al3Ti/Al/Al2O3 composite obtained by powder metallurgy method
Anna Świderska-Środa*, Krzysztof J. Kurzydłowski**, Jerzy W. Wyrzykowski** *Centrum Badań Wysokociśnieniowych PAN, ul. Sokołowska 29/37, 01-142 Warszawa **Politechnika Warszawska, Wydział Inżynierii Materiałowej, ul. Wołoska 141, 02-507 Warszawa
Annals 4 No. 11, 2004 pages
DOI:
keywords:
abstract The study was devoted to investigations of fine-grained composite with the matrix composed of Al3Ti intermetallic phase, obtained by powder metallurgy. Two-phase Al3Ti/Al alloy with chemical composition of Al-21% at. Ti and dendritic microstructure (Fig. 1) was obtained by conventional ingot metallurgy. Subsequently, the ingot was mechanically milled for 5 hours in a ball mill at 250 rpm in ethyl alcohol. Nanocrystalline powder (Fig. 2b) with specific surface 6.38 m2/g contained the Al3Ti phase and aluminium in a proportion close to that of the cast alloy. The powder was sintered by free sintering at 1100°C for 1 hour in vacuum 10−3 Pa. The high temperature process resulted in aluminium being partially oxidised to Al2O3 phase. The structure of the sinter contained fine Al3Ti grains separated from one another by metallic aluminium, and Al2O3 oxide particles (Fig. 3). Sinter exhibited attractive combination of mechanical properties; fracture toughness received using indentation method equal to 6 MPa⋅m1/2, microstrohardness (HV02) 524 and elastic modulus on the order of 200 GPa. The metallic aluminium present in the sinter functioned as a relaxation agent for the stresses induced during the plastic deformation of the intermetallic Al3Ti phase. The large aluminium oxide particles improved their fracture toughness by elongating the crack development path. Key words: Al3Ti intermetallic phase, powder metallurgy, structure of the composite