激光表面重熔对双态组织TC4合金力学性能和摩擦学性能的影响

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

摘要:

TC4合金是应用最广泛的航空材料之一，激光表面重熔（laser surface remelting, LSR）技术可有效提升材料力学性能，但是LSR对于双态组织TC4合金力学性能的增强机理尚不明确。本文在TC4试样的正面和背面进行LSR处理，随后进行力学性能和磨损性能测试，利用TEM、EBSD、SEM等仪器进行系统表征，讨论了层状异构和双相结构起到的增强协同作用机制。结果表明：重熔层由粗大板条马氏体（coarse lath martensite, CLM）和杂乱无章的细小板条马氏体（fine lath martensite, FLM），以及部分平行分布的压缩孪晶组成。在发生塑性形变时，位错在CLM中产生、缠绕和塞积，FLM和孪晶包裹在CLM周围，限制了CLM中位错滑移的传递，最终使双态组织TC4钛合金的屈服强度显著增加到(879±6) MPa，抗拉强度显著增加到(1035±11) MPa，磨损时的疲劳裂纹数量显著减少。

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.