Effect of Laser Surface Remelting on Mechanical and Tribological Properties of TC4 Alloy with Bimodal Microstructure

Abstract:

TC4 alloy is one of the most widely used aviation materials. Laser surface remelting (LSR) technique can effectively improve the mechanical properties of TC4 alloy, but the strengthening mechanism of LSR on the mechanical properties of TC4 alloy with bimodal microstructure is still unclear. In this study, LSR treatment was conducted on the front and back of TC4 samples, and then the mechanical properties and tribological properties were tested. Systematic characterization was performed by TEM, EBSD, SEM, and other instruments. The synergistic strengthening mechanism between layered heterogeneous structure and bimodal microstructure was discussed. The results show that the remelted layer is composed of coarse lath martensite (CLM), fine lath martensite (FLM) with scattered orientations, and partially parallel compression twins. When the remelted layer undergoes plastic deformation, dislocations are activated, tangled, and piled-up in CLM. FLM and twins wrapped around CLM hinder the transfer of dislocation slip at the interface, resulting in a significant increase in the yield strength of TC4 alloy with bimodal microstructure to (879±6) MPa, an increase in tensile strength to (1035±11) MPa, and a reduction in number of the fatigue cracks during wear testing.