The surface tension of molten aluminum and Al-Si-Mg alloy under vacuum andhydrogen atmospheres

The surface tensions of pure molten aluminum, A356 alloy (Al-7 pet Si-0.3 p et Mg), and strontium-modified A356 alloy have been measured under vacuum a nd hydrogen atmospheres using the sessile drop technique. The values obtain ed for pure aluminum at 680 degrees C and for A356 alloy and modified A356 alloy at 630 degrees C are 1.007, 0.889, and 0.844 N/m, respectively, when measured under vacuum. The addition of hydrogen gas to the atmosphere of th e liquid droplet has no significant effect on the surface tension of the un modified A356 alloy, while it lowers the surface tension of the modified al loy to 0.801 N/m. This effect is possibly due to the formation of SrH2.