1 State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metal, Lanzhou University of Technology, Lanzhou 730050, China 2 School of Materials Engineering, Lanzhou Institute of Technology, Lanzhou 730050, China
Cite this article:
Peng JIN,Ran SUI,Fuxiang LI,Weiyuan YU,Qiaoli LIN. Reactive Wetting of TC4 Titanium Alloy by Molten 6061 Al and 4043 Al Alloys. Acta Metall Sin, 2017, 53(4): 479-486.
In order to improve the inoxidizability of TC4 alloy at high temperatures, hot dip aluminizing process is an efficient and economical way for industrial application. In this process, the wetting of TC4 alloy by molten Al alloy is the main factor which determined the coating quality. In this work, wetting of TC4 alloys by two industrial grade Al alloys (i.e., 6061 Al and 4043 Al alloys) were studied by using the modified sessile drop method at 600~700 ℃ under high vacuum. The results show that Al/Ti system is a typical reactive wetting, and the spreading dynamics can be described by reaction product control model, further the whole wetting behavior can be divided into two stages: the first stage for the nonlinear spreading and the second stage for the linear spreading. The small amount of alloying element Si in the Al alloys can cause significantly segregation at liquid/solid interface and formation of the Si-rich phase (Ti7Al5Si12). Ti7Al5Si12 decomposition is responsible for the nonlinear spreading, and Ti7Al5Si12 decomposition and Al3Ti formation are together responsible for the linear spreading. The formation of precursor film accompanies with the good final wettability.
Table 1 Nominal chemical composition of materials (mass fraction / %)
Fig.2 Variation of contact angles (a) and normalized contact radii (b) with time of molten 6061 Al and 4043 Al alloys on the surface of TC4 substrate (Rd and R0—the dynamic and initial contact radii, t—time for isothermal wetting)
Fig.3 SEM images for 6061 Al/TC4 system after isothermal wetting at 600 ℃ (a) cross-sectional view (Inset shows the high magnified image) (b) top view at the close of triple line (c) high magnified image of rectangular zone in Fig.3b (d) interfacial microstructure and element line distributions
Fig.4 SEM images for 4043 Al/TC4 system after isothermal wetting at 600 ℃ (a) at the close of triple line (b) central position of interface and element line distributions
Fig.5 SEM images for 4043 Al/TC4 system after isothermal wetting at 650 ℃ (a) cross-sectional view (b) top-view at the close of triple line (c) high magnified image of rectangle zone in Fig.5b (d) interfacial microstructures and element line distributions
Fig.6 Macro-morphologies and SEM images for Al/TC4 samples after Al was removed by NaOH solution (a) macro-morphology for 4043 Al/TC4 sample (b, c) corresponding details in Fig.6a (d) macro-morphology for 6061 Al/TC4 sample (e, f) corresponding details in Fig.6d
Fig.7 XRD spectra of the phases at the precursor films for 6061 Al (a) and 4043 Al (b) samples after isothermal wetting at 700 ℃, the exposed interface of 4043 Al/TC4 after isothermal wetting at 650 ℃ through removing of the solidified Al (c), the exposed interface of 6061 Al/TC4 after isothermal wetting at 650 ℃ through removing of the solidified Al (d), and the original surface of TC4 alloy (e)
Fig.8 Arrhenius plot of the kinetic constant k1 and k2
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