The effect of Hf and Ti additions on microstructure and properties of Cr2Nb–Nb in situ composites

The present paper describes the effect of Hf and Ti additions on the microstructures and mechanical properties of two-phase composites based on the Cr2Nb–Nb eutectic. The microstructures of directionally solidified in situ composites containing 50–70% by volume of the Laves phase Cr2Nb which was modified with Hf (7.5–9.2%) and Ti (16.5–26%) are described. Partitioning of Hf and Ti between the two phases is discussed using microprobe and EDS results. The tensile properties at 1100 and 1200 °C are described and compared with those of an analogous niobium silicide-based composite. The Cr2(Nb)–(Nb) composite tensile yield strengths at 1200 °C were increased over that of monolithic Cr2Nb to ∼130 MPa. However, at 1200 °C the yield strengths of the silicide-based composites were approximately twice those of the Cr2(Nb)–(Nb) composites.

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Oxidation resistance and mechanical properties of Laves phase reinforced Cr in-situ composites

Intermetallics ◽

10.1016/s0966-9795(00)00046-7 ◽

2000 ◽

Vol 8 (9-11) ◽

pp. 1111-1118 ◽

Cited By ~ 33

Author(s):

M.P. Brady ◽

J.H. Zhu ◽

C.T. Liu ◽

P.F. Tortorelli ◽

L.R. Walker

Keyword(s):

Mechanical Properties ◽

Oxidation Resistance ◽

Laves Phase ◽

In Situ Composites

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Microstructure Evolution and Compression Properties of a Directionally Solidified Ni-24.8%Nb Hypereutectic Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.1351 ◽

2010 ◽

Vol 654-656 ◽

pp. 1351-1354

Author(s):

Shuang Ming Li ◽

Bing Lun Jiang ◽

Heng Zhi Fu

Keyword(s):

Mechanical Properties ◽

Microstructure Evolution ◽

Growth Velocity ◽

Thermal Gradient ◽

Hypereutectic Alloy ◽

Directionally Solidified ◽

In Situ Composites ◽

Compression Properties ◽

Deformation Behaviors

At normal solidification conditions, in-situ composites of a Ni-24.8%Nb hypereutectic alloy can be produced at growth velocities below 5μm/s, with a thermal gradient of 180K/cm, and this low productivity remarkably restricts the application of this kind of in-situ composites. In this paper, we proposed an approach that employs an abrupt growth velocity to make the in-situ composites grow stably out of the coupled zone. In-situ composites of the Ni-24.8%Nb hypereutectic alloy were obtained at a growth velocity of 100μm/s and the productivity was greatly improved. This value is in the same order magnitude imposed on the single-crystal superalloys. The compression strengths were investigated on different microstructures involving the coupled eutectics and non-coupled eutectics. The results showed that the crack distribution and extension were mainly localized in primary Ni3Nb dendrites in the non-coupled eutectics, and that in-situ composites with the entirely coupled eutectics have improved mechanical properties and different deformation behaviors.

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MICROSTRUCTURES AND MECHANICAL PROPERTIES OF Al2O3-BASIC EUTECTIC IN SITU COMPOSITES DIRECTIONALLY SOLIDIFIED BY LASER FLOATING ZONE REMELTING

ACTA METALLURGICA SINICA ◽

10.3724/sp.j.1037.2012.00419 ◽

2012 ◽

Vol 48 (12) ◽

pp. 1479

Author(s):

Xiaojiao JIA ◽

Jun ZHANG ◽

Haijun SU ◽

Kan SONG ◽

Lin LIU ◽

...

Keyword(s):

Mechanical Properties ◽

Floating Zone ◽

Directionally Solidified ◽

In Situ Composites ◽

Microstructures And Mechanical Properties

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Analyses of The Eutectoid Phase Transformation in Complex Ds Nb-Silicide In-Situ Composites

Microscopy and Microanalysis ◽

10.1017/s1431927600032293 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 1244-1245

Author(s):

S.D. Sitzman ◽

B.P. Bewlay

Keyword(s):

Crystal Structure ◽

Pattern Analysis ◽

Electron Backscatter Diffraction ◽

Czochralski Method ◽

Directionally Solidified ◽

Two Phase ◽

In Situ Composites ◽

Structural Applications ◽

Backscatter Diffraction

In-situ composites based on (Nb) and Nb silicides, such as Nb5Si3 (tI32 crystal structure) and Nb3Si (tP32 crystal structure), are being investigated for revolutionary high-temperature structural applications [1,2]. The use of Hf and Ti alloying additions to these silicides has also been examined; in these systems Nb5Si3 has also been observed with the hP16 structure. The present paper describes EBSD analyses of a directionally solidified (DS) Nb-silicide based composite that experienced a eutectoid transformation. The composites were directionally solidified using the Czochralski method as described previously [1]. The composites were creep tested at 1200°C for 24 hours. Microstructure and microtexture characterization were performed using scanning electron microscopy, and electron backscatter diffraction pattern analysis (EBSD).The microstructure of a composite directionally solidified from a Nb-12.5Hf-33Ti-16Si alloy is shown in Figure 1. in the as-DS condition the microstructure consisted of primary (Nb)3Si dendrites and coarse (Nb)3Si-(Nb) two-phase cells.

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