Using electrical resistivity measurements, optical microscopy and scanning electron microscopy (SEM) with energy dispersive x-ray analysis (EDX), the Al-rich corner of the Al-Zr-Hf phase diagram was studied. In the investigation the combined solubility of Zr and Hf in solid Al at 600, 500, and 400 A degrees C was determined. Zr and Hf significantly decrease the solubility of each other in solid Al with significant contraction of the Al single phase field with decreasing temperature. Investigation established only two solid phases in equilibrium with Al solid solution, ZrAl(3) and HfAl(3), with no apparent solubility of either Zr in HfAl(3) or Hf in ZrAl(3). Taking into account the established extension of the Al single phase field and compositions of the ZrAl(3) and HfAl(3) compounds in equilibrium with Al solid solution, the partial isothermal sections of the Al-Zr-Hf phase diagram at 600, 500, and 400 A degrees C were constructed.