Landolt-Bornstein (via Portico)
Includes 10-volume series: Phase Equilibria, Crystallographic and Thermodynamic Data of Binary Alloys. You can browse the volumes in Portico, then the table of contents for your alloy.
The volumes are sorted by the book subtitle, which is the range of alloys covered. The first volume (Ac-Au – Au-Zr) is in the A's. The other volumes: B-Ba – C-Zr, Ca-Cd – Co-Zr, Cr-Cs – Cu-Zr, Dy-Er – Fr-Mo, Ga-Gd – Hf-Zr, Li-Mg – Nd-Zr, Ni-Np – Pt-Zr, and Pu-Re – Zn-Zr. If there are 2 copies, the later one is probably a supplement. They're sorted in the contents by the first element so Li-Mg – Nd-Zr will be in the L's under "Li." There's also one volume for ternary alloys - Phase Diagrams and Physical Properties of Nonequilibrium Alloys · Nonequilibrium Phase Diagrams of Ternary Amorphous Alloys (filed under the N's).