Thin film metallic glasses for substrate fatigue property improvements
Haoling Jia (University of Tennessee), Fengxiao Liu (University of Tennessee), Zhinan An (University of Tennessee), Weidong Li (University of Tennessee), Gongyao Wang (University of Tennessee), Jinn Chu (Nat'l Taiwan Univ. of Sci.Tech), Jason Jang (National Central University), Yanfei Gao (University of Tennessee), Peter Liaw ()
Mechanics of Thin Films and Multilayered Structures
Wed 9:00 - 10:30
Salomon 203
Amorphous metallic films, a thin form of metallic glasses, have been attracting more and more attention in the last two decades. Compared with the conventional crystalline films, amorphous metallic films exhibit unique properties, such as high strength, high toughness, large elastic limits, and high-corrosion resistance, despite that some of their properties and characteristics are not as good as the metallic or ceramic films. However, the deformation mechanisms of thin film metallic glasses (TFMGs) are still far from in-depth studies. This work will focus on reviewing and discussing the fatigue behavior of some structural-material substrates coated with TFMGs. The substrate materials include a 316L stainless steel, Al-based, Ni-based, Zr-based, and Ti-based alloys. The results show that the four-point-bending fatigue life of the substrates is greatly improved by Zr- and Cu-based TFMGs, while the Fe-based TFMG, TiN, and pure-Cu films are not so helpful in the fatigue-life extension of the substrates. In comparison, the tension-tension fatigue lifetime and endurance limit of the 316L stainless steel cannot be improved by the Zr- and Cu-based TFMGs. Moreover, the annealed TFMGs can further improve the fatigue behavior than the as-deposited TFMGs. The fatigue mechanisms of the crystalline and BMG materials, together with the TFMGs, are discussed in the present work. The fatigue-damage mechanisms of the crystals and BMGs show obvious difference, by presenting 3-stage and 4-stage fatigue deformation processes, respectively. In the present work, a synergistic experimental/simulation study was conducted to investigate the micro-mechanisms of the fatigue behavior of TFMGs adhered to the substrates, as well as the film adhesion and thickness effects on fatigue behavior of the substrate. Furthermore, the shear-band initiation and propagation under bending deformation will be investigated with the Rudnicki-Rice instability and free-volume theories in finite-element modeling.