The microstructural changes in the matrix and equilibrium phases of Al-(Ti)-V-Zr alloys (respectively, VZ1, TVZ4 and TVZ1-3) have been investigated using XRD, SEM, EDS and TEM. The alloys were made by RSP(Rapid Solidification Process) to obtain the supersaturated solid solution. The sample preparation was conducted in the vacuum or under an inert gas condition to prevent the oxidation. The preaging was conducted at 500℃ for one hour to suppress the formation of the cellular phase which may have a bad effect on the mechanical properties, and then they were aged to observe the coarsening behavior of the metastable $L1_2$ precipitates at 425℃ for 100 hrs., 200 hrs. and 400 hrs.
Equilibrium phases are characterized to be $Al_{10}V$, $D0_{22}$ and $D0_{23}$ in the case of VZ1, and $D0_{22}$ and $D0_{23}$ in the case of TVZ4 and TVZ1-3. The coarsening rates of cubic $Al_3(V_{.676}Zr_{.324})$, $Al_3(Ti_{.156}V_{.25}Zr_{.594})$ and $Al_3(Ti_{.1}V_{.4}Zr_{.5})$ precipitates were measured by TEM DF images. Most of the spherical $Ll_2$ $Al_3M$ precipitates are observed to be coherent with the matrix and lattice mismatches of those are measured to be -0.0060, 0.0059 and -0.0061, respectively, by SAD pattern in TEM micrographs. The coarsening kinetic constants of all the alloys are in order of $10^{-29}$ which are very low values and mainly due to low lattice mismatch.
Average particle radius of $Ll_2$ phases is about 4 nm and particle size distribution obeys LSW theory. Also, in the matrix, no phase transformations from $Ll_2$ to $D0_{22}$ or $D0_{23}$ are observed. Calculated values of the $Ll_2$/matrix interfacial energy are very close to those of coherent ones. Due to the low coarsening rate and the thermal stability of $Ll_2$ phases, the Al-Ti-V-Zr system shows a promise as a basis for a high temperature Al alloys.
