Bulk nanocrystalline matrix alloys and composites may have potential for applications involving high strength at ambient and elevated temperatures. Lightweight Al-base alloys with nanocrystalline dispersed phase of intermetallics and oxides within a solid solution matrix have been synthesized in this study. By varying the composition of the alloys containing primarily Al, Si and Y, either an Al-rich or Si-rich matrix having different microstructures and mechanical properties can be produced. Mechanical milling method has been used to disperse the phases and oxides in the nanometer scale. Evolution of crystalline phases during consolidation processing was monitored by XRD and DSC. Typical room temperature strength of these alloys are in the range of 1200 - 1300 MPa, with excellent high temperature strength.