Dependence of Mechanical Properties of Platinum-Rhodium Binary Alloys on Valence Electron Parameters

Dependence of mechanical properties of binary Pt-Rh alloys on valence electron ratio (VER), number valence electrons (ev), and average atomic number of the alloys (Z) are investigated. The alloys have high number of valence electrons (9 ≤ ev ≤ 10) and a wide range of the average atomic number (Z = 45–78). Clear correlations between VER of the alloys and their mechanical properties are found. By increasing the VER of the alloy from 0.13 to 0.20 following the increase of Rh content in the composition, the hardness, elastic modulus, and ultimate tensile strength of the alloy increases. Creep rates of the selected alloys clearly decrease with increasing VER at high temperatures (1500-1700 ℃C), whilst stress rupture time at different temperatures consistently increases because of higher Rh content in the alloy solid solution chemistry. Dependence of mechanical properties on valence electron parameters is discussed with reference to the atomic bonding.