Abstract
Nanocrystalline (NC) materials have fascinating physical and chemical properties, thereby they exhibit great prospects in academic and industrial fields. Highly efficient approaches for fabricating bulk NC materials have been pursued extensively over past decades. However, the instability of nanograin, which is sensitive to processing parameters (such as temperature and time), is always a challenging issue to be solved and remains to date. Herein, we report an ultrafast nanostructuring strategy, namely ultrasonic vibration consolidation (UVC). The strategy utilizes internal friction heat, generated from mutually rubbing between Ti-based metallic glass powders, to heat the glassy alloy rapidly through its supercooled liquid regime, and accelerated viscous flow bonds the powders together. Consequently, bulk NC-Ti alloy with grain size ranging from 10 to 70 nm and nearly full density is consolidated in 2 seconds. The novel consolidation approach proposed here offers a general and highly efficient pathway for manufacturing bulk nanomaterials.
Highlights
Once the grain size is refined to nanometer scale, the polycrystalline materials tend to exhibit excellent physical and chemical properties[1,2,3,4,5]
One approach is to refine grains by severe plastic deformation (SPD), which involves a complex stress state resulting in equiaxed grains with high-density dislocations
A new method, ultrasonic vibration consolidation (UVC), is developed to fabricate bulk NC-Ti alloy starting from the MG powders (MGPs) precursor
Summary
It can be calculated that the contact radius ranges from about 600 to 900 nm at different preset pressure, resulting in the maximum contact stress larger than 10 GPa. Besides, the high speed vibration induces rapid rubbing between powders, the friction converts kinetic energy into thermal energy, leading to flash heating at the contact area. Based on the contact temperature caused by flash heating, the maximum heating rate can be estimated to be as high as 4 × 107 K/min, which is 4 orders of magnitude higher than that of traditional fast sintering[30] The flash heating of UVC coupled with the accelerated viscous flow of the metallic glass lead to the rapid densification to approach the theoretical density in 2 s, the UVC offers an efficient pathway to fabricate bulk nanocrystalline materials
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