Materials Science Forum, Vol.449-4, 809-812, 2004
Thermal stability and mechanical properties of nanocrystalline L1(2) Al3Hf and (Al+12.5 at.%Zn)(3)Hf prepared by MA and SPS
Thermal stability and mechanical properties of L1(2) Al3Hf and (Al+12.5 at.%Zn)(3)Hf synthesized by mechanical alloying(MA) and spark plasma sintering(SPS) were investigated. Nanocrystalline L1(2) phase was produced after MA for 8 and 10 hrs in Al3Hf and (Al+12.5 at.%Zn)(3)Hf powders, respectively. The grain sizes were reduced to about 10 nm in both systems after MA for 20 hrs. After SPS, L1(2) phase was maintained only in Zn added system. In (Al+12.5 at.%Zn)3Hf, L 12 to D0(23) phase transformation was started at about 850degreesC and finished at about 1150degreesC. Microhardness was decreased with increasing the annealing temperature while fracture toughness was increased due to the grain growth. Fracture toughness of (Al+12.5 at.%Zn)3Hf was greater than that of Al3Hf in all annealing temperatures. Fracture toughness of (Al+12.5 at.%Zn)3Hf after annealing at 1200 degreesC was 12 about 5.38 MPam(1/2).
Keywords:nanocrystalline intermetallics;Hafnium trialuminide;mechanical alloying;spark plasma sintering