Temperature-Induced Enhancement of Tensile Strength of Perforated Ti-6al-4v Sheet Revealed Through Mechanical-Thermal Coupling Quasi-Static Tension

In order to investigate the effect of temperature on the tensile strength of perforated Ti–6Al–4V (TC4) alloy, the tensile mechanical properties of TC4 alloy with various micro-hole array distributions were obtained at a temperature in a range from 20 °C to 500 °C by using a novel mechanical-thermal coupling tensile test instrument developed by ourselves. The experimental results showed that the tensile strength of all types of TC4 alloy specimens decreased with the increase in temperature, and the elastic modulus of most types of TC4 alloy specimens decreased with the increase in temperature. The tensile strength of the perforated specimen iii was 14.8% lower than that of the solid specimen and the elastic modulus of perforated specimen ii was 5.5% lower than that of the solid specimen at room temperature (RT), and all types of the perforated specimens continued to exhibit relatively lower tensile strengths and elastic modulus at 180 °C and 340 °C. Abnormally, the tensile strength of the perforated specimen iii was 2.1% higher than that of the solid specimen and the elastic modulus of perforated specimen ii was 23% higher than that of the solid specimen at 500 °C. With the increase of temperature from 20 °C to 500 °C, the fracture mode of the solid specimen gradually changed from equiaxed dimple to shear dimple. Regarding the perforated specimens, the cracks and dimples adjacent to the holes gradually decreased as a function of temperature. The existence of prefabricated holes in the specimens dissipated part of the thermal stress, maintained the integrity of the micro-hole structure, and made the nearby section relatively flat, which induced a relatively higher tensile strength and structural stiffness at an elevated temperature. The relatively lower stress in the gauge section of the perforated specimens obtained through finite element analysis also indicated the temperature-induced enhancement of tensile strength.