2011 Volume 52 Issue 8 Pages 1661-1666
This study attempted to investigate the high temperature tensile deformation behaviour of new Al-1%Mg-1.1%Si-0.8%CoNi heat resistant aluminium alloy. New aluminium alloy strengthened by Co-Ni based phase was manufactured by using powder ball milling and continuous casting, based on the alloy design & preliminary test. High temperature tensile tests were conducted at various temperatures from 298 K to 723 K. OM, SEM, EPMA, XRD, FIB and HR-TEM equipments were used to analyse microstructure, phases, and fracture surface. Microstructure of the new alloy mainly consisted of Al matrix and Co-Ni based phases (1∼8 μm). The Co-Ni based phase was analyzed and confirmed as (Ni, Co)3Al4 having incoherent interface with matrix. In high temperature tensile results, the new aluminium alloy didn’t show significant decrease (19.6%) of strength with increasing temperature (723 K), suggesting totally different behaviour vis-a-vis conventional A319 alloy (87.0% decrease of T.S.). Fractography observation results of new alloy represented the ductile fracture mode with dimples. Voids were mainly initiated at Co-Ni based strengthening phases. It was apparently observed that the strengthening effect of the (Ni, Co)3Al4 could be still maintained at high temperature of 723 K. The deformation mechanism of this alloy was also discussed.