Two kinds of Al-Ti-Zr alloys were prepared to investigate the coarsening of the spherical L1(2)-structured Al-3(Ti,Zr) precipitates aging at 425 C for various periods of time. The results indicated that the increasing of Zr-content would result in increasing the coarsening rate of the precipitates. The coarsening coefficients of L1(2)-structured Al-3(Ti0.25Zr0.75) and Al-3(Ti0.25Zr0.25) precipitates in these Al-5 vol.% Al-3(Ti,Zr) alloys are 3.94 x 10(-28) and 1.61 x 10(-28) m(3) h(-1), respectively. In addition, the higher Zr-content Al-3(Ti0.25Zr0.75) precipitates became unstable and formed a kind of complex precipitates after aging for a long period of time. The hardness data shows that the peakaging of both two alloys were aging at 425degreesC for 100h, and the peakaging hardness of Al-0.65Ti-3.22Zr and Al-1.74Ti-1.14Zr alloys were HV 75 and HV 78, respectively. The hardness of Al-0.65Ti-3.22Zr alloy was slightly lower than that of Al-1.74Ti-1.14Zr alloy due to the faster coarsening rate of the Al-3(Ti0.27Zr0.75) precipitates. (C) 2002 Elsevier Science B.V. All rights reserved.