Showing papers by "Hongbin Bei published in 2007"
TL;DR: In this article, single-crystal micro-pillars of a molybdenum alloy were prepared by a new technique that involves chemically etching away the matrix of a directionally solidified NiAl-Mo eutectic.
288 citations
TL;DR: In this paper, the effects of focused ion beam (FIB) milling on mechanical behavior were investigated on a Mo-alloy single crystal to investigate effects of FIB on mechanical behaviour.
Abstract: Nanoindentation was performed on a Mo-alloy single crystal to investigate effects of focused ion beam (FIB) milling on mechanical behavior. On a non-FIB-milled surface, pop-ins were observed on all load-displacement curves corresponding to a transition from elastic to plastic deformation. Similar pop-ins were not detected on surfaces subjected to FIB milling. This difference indicates that FIB milling introduces damage that obviates the need for dislocation nucleation during subsequent deformation. A second effect of FIB milling is that it increased the surface hardness. Together, these effects could be the source of the size effects reported in the literature on micropillar tests.
168 citations
TL;DR: In this paper, Wang et al. summarized the recent development in this area and found that all newly developed parameters can be grouped into three basic categories according to their definitions, and the universal GFA indicator? is still the best in terms of reliability and applicability.
99 citations
TL;DR: In this paper, a soft layer ∼500μm thick was detected near the surface with both hardness and elastic modulus increasing from the surface to the interior, suggesting that surface softening may be the result of freezing-in of excess defects.
Abstract: Contrary to the cooling-rate induced hardening observed in crystalline metals, the authors report here an unexpected surface softening in rapidly solidified Zr50Cu50 bulk metallic glass. A soft layer ∼500μm thick was detected near the surface with both hardness and elastic modulus increasing from the surface to the interior. To understand the reason for this, a correlation between cooling rate and defect concentration was derived. Defect concentration was found to increase as the cooling rate increased, suggesting that surface softening may be the result of freezing-in of excess defects, induced by a faster cooling rate near the surface compared to the interior.
73 citations
TL;DR: In this article, two kinds of well-aligned fibrous microstructures produced by directional solidification of NiAl-Mo and Fe-Fe2Ta eutectics are reviewed.
Abstract: This paper reviews two kinds of well-aligned fibrous microstructures produced by directional solidification of NiAl-Mo and Fe-Fe2Ta eutectics. In both these composites, fiber size and spacing decrese inversely as the square root of the growth rate. Tensile tests as a function of temperature showed that the NiAl-Mo composite has a higher yield strength and lower ductile-to-brittle transition temperature than the NiAl matrix. For the Fe-Fe2Ta composite, yield strengths in excess of 700 MPa were obtained at temperatures to 600°C, with elongations to fracture of ~3% which remained roughly constant at temperatures to 950°C.
6 citations