Elastic moduli of cast Ti–Au, Ti–Ag, and Ti–Cu alloys

Summary 

Objectives

This study investigated the effect of alloying titanium with gold, silver, or copper on the elastic properties of the alloys.

Methods

A series of binary titanium alloys was made with four concentrations of gold, silver, or copper (5, 10, 20, and 30mass%) in an argon-arc melting furnace. The Young's moduli and Poisson's ratios of the alloy castings were determined with an ultrasonic-pulse method. The density of each alloy was previously measured by the Archimedes' principle. Results were analyzed using one-way ANOVA and the Scheffé's test.

Results

The densities of Ti–Au, Ti–Ag, and Ti–Cu alloys monotonically increased as the concentration of alloying elements increased. As the concentration of gold or silver increased to 20%, the Young's modulus significantly decreased, followed by a subsequent increase in value. As the concentration of copper increased, the Young's modulus monotonically increased. The Young's moduli of all the Ti–Cu alloys were significantly higher than that of the titanium.

Significance

The density of all the experimental alloys was virtually independent of the alloy phases, while the Young's moduli and Poisson's ratios of the alloys were dependent. The addition of gold or silver slightly reduced the Young's modulus of the titanium when the alloy phase was single α. The increase in the Young's modulus of the Ti–Cu alloys is probably due to the precipitation of intermetallic compound Ti₂Cu. Copper turned out to be a moderate stiffener that gains a Young's modulus of titanium up to 20% at the copper concentration of 30mass%.

Keywords: Titanium alloy, Casting, Young's modulus, Poisson's ratio, Density