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Melt-spinning was successfully used to fabricate continuous Fe–6.5wt.%Si ribbons of 35 μm in thickness and 50–60 mm in width. Equiaxed grains measuring 2.4 ± 1.0 μm and columnar grains measuring 1.69 ± 0.72 μm were observed on the wheel and free surfaces, respectively. The as-spun ribbons showed strong 〈100〉 fiber texture, excellent room-temperature ductility, and very low core losses at high frequencies above 10 kHz. Compared with other fabricating techniques, the present work verified the feasibility for melt-spinning technique to fabricate ribbons of Fe–6.5 wt%Si with large-scale and thus cost-effective.

We demonstrate excellent superelasticity and giant elastocaloric effect in a directionally solidified Co50.7V33.3Ga16 alloy. Owing to the formation of [001]A preferentially oriented columnar grains, the as-grown alloy displays nearly perfect superelastic behaviors with fully reversible compressive strain of up to 5.4%, narrow stress hysteresis of about 40 MPa and a wide operating temperature window from 258 to 373 K. Simultaneously, a giant adiabatic temperature change ΔTad of -18.7 K is obtained on removing a uniaxial stress of 400 MPa at room temperature, which is in good agreement with the theoretical values based on Maxwell relation (-19.0 K) and calorimetric measurements (-19.9 K). A large |ΔTad| of greater than 12.5 K is obtained over a wide temperature span of at least 115 K. Moreover, both superelasticity and elastocaloric effect remain good functional stability without any evident degradation for 100 cycles.

Here we present a novel concept that uses a low volume fraction of nanoparticles to nano-treat Fe-Ti-B melts for a new high performance high modulus steel (HMS). Microstructures of the nano-treated Fe-Ti-B HMS were investigated. The nano-treated HMS consists of fine TiB2 particles and a strengthening phase of unexpected ultrafine Fe2B lamellas. While Fe2B phase is traditionally considered to be detrimental in steel making due to its inherent embrittlement effect, this study shows a successful conversion of the detrimental Fe2B phase into an advantageous one. The nano-treated HMS has significantly higher tensile strength compared to its conventionally made counterpart, 950 MPa vs. 510 MPa, while retaining the high Young's modulus, low density, and ductility. This new concept effectively demonstrates the successful structural refinement in Fe-Ti-B system using nanoparticles, without changing the solidification rate, which eliminates the dilemma between achieving enhanced mechanical properties versus manufacturing for mainstream applications and enables the use of stiff HMS for lightweighting of practical applications. A new mechanism of nanoparticle-induced solute enrichment at nanoscale in alloy melts was also proposed and has implications for new manufacturing routes of metals.

The omega phase in as-cast high-Nb-containing TiAl alloy exhibits particles with sizes on the nano- or microscale within the B2 matrix. Omega particles are transformed from the B2 phase by heterogeneous nucleation on the B2/γ boundaries or homogeneous nucleation within the B2 phase. After annealing at 900 °C, the omega particles disappear and transform into B2 phase. The transformation is rapidly initiated, but is difficult to complete.

The microstructures of high-Nb-containing TiAl alloys with a nominal composition of Ti–53Al–18Nb (at.%) having a γ 1 + γ phase region were studied. The range of Al and Nb content in which the γ 1 phase is able to precipitate has been determined. High Al content and high Nb content favor the precipitation of the γ 1 phase in the γ matrix. The distribution and morphology of the γ 1 phase in the γ matrix were also studied.

The orientation relationship (OR) between the TiN and Ti2AlN phases in the nitride layer during the oxidation of TiAl-based alloy at 900 degrees C was determined by transmission electron microscopy (TEM). The OR is (111)(TiN)parallel to(0001)(Ti2AlN), [0 (1) over bar1](TiN) parallel to [11 (2) over bar 0](Ti2AlN). Al can reduce the twin boundary energy of TiN, leading to the formation of many stacking faults in the Al-enriched TiN phase. The Ti(2)AIN phase forms at the bottom of the TiN phase when the Al content is sufficient to induce phase transformation. Phase transformation was identified in the Ti2AlN phase after electron irradiation for about 40 s. (c) 2007 Published by Elsevier Ltd. on behalf of Acta Materialia

The orientation relationship (OR) and the interface structure between TiB precipitate and gamma-TiAl phase have been investigated using high-resolution electron microscopy. The OR was determined to be [0 (1) over bar0](TiB)parallel to[1 (1) over bar0](gamma), (100)(TiB)parallel to(11 (2) over bar)gamma: This OR has been predicted precisely by the method of coincidence of reciprocal lattice points. The basic vector transformation matrix was also calculated. Based on the investigation of the interface structure, the morphology of the TiB precipitate was discussed from the viewpoint of interface energy. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.