Investigating the Evolution of Mechanical Properties in Aluminum Alloy after Thermal Degradation with Laser Ultrasonic Technology

Abstract

To overcome the limitation that thin-walled aluminum alloy can't monitor many mechanical parameters in real time during service and it is difficult to understand the deformation mechanism, the acoustic characteristics of 6061-T6 aluminum alloy under different heat treatment conditions are analyzed in detail by using nondestructive laser ultrasonic technology (LUT). By comparing the key acoustic indexes obtained in time-frequency domain analysis with the results of traditional tensile test and hardness test, we deeply discuss the mechanical properties of materials. Using the microstructure changes observed by optical microscope, we revealed the root of the variation of mechanical properties under different heat treatment conditions. It is found that there is a significant correlation between wave velocity parameters and elastic modulus, strength and hardness of 6061-T6 aluminum alloy. In addition, according to the peak values of acoustic indexes such as amplitude change rate, weighted peak frequency, power and bandwidth at 200 ℃, we divide the deformation process of aluminum alloy into two stages: (25-200 ℃) and (200-400 ℃), in which 200 ℃ marks the key turning point of dynamic recrystallization of aluminum alloy. This study confirmed that through the key acoustic indexes extracted by LUT technology, we can deeply understand the performance evolution and internal working mechanism of aluminum alloy under different heat treatment conditions.

Keywords: Laser ultrasonic technology, Mechanical properties, Deformation mechanism, Aluminum alloy, Heat treatment