Room-temperature mechanical behavior of cryomilled al alloys

An experimental investigation into ratcheting strain and stress-strain hysteresis loop in stress-controlled cyclic tensile tests at room temperature was performed to determine the effect of loading frequency on the cyclic mechanical behavior of highdensity polyethylene (HDPE). It was found that frequencies ranging from 0.01 Hz up to 1 Hz mostly affects the accumulated strain over related time scales (i.e that of the cycle itself) and not over long time scale (i.e. during the full test). In addition, the higher the frequency is, the more closed and vertical the loops are. Furthermore, the frequency affects only on the kinetics of stabilization of ratcheting strain but not on one of hysteresis loop.

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Mechanical Behavior of 2D C/SiC Composites at Elevated Temperatures under Uniaxial Compression

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.462-463.1 ◽

2011 ◽

Vol 462-463 ◽

pp. 1-6 ◽

Cited By ~ 1

Author(s):

Tao Suo ◽

Yu Long Li ◽

Ming Shuang Liu

Keyword(s):

Compressive Strength ◽

High Temperature ◽

Carbon Fiber ◽

Mechanical Behavior ◽

Uniaxial Compression ◽

Room Temperature ◽

Elevated Temperatures ◽

Carbon Matrix ◽

Structural Applications ◽

Sic Composites

As Carbon-fiber-reinforced SiC-matrix (C/SiC) composites are widely used in high-temperature structural applications, its mechanical behavior at high temperature is important for the reliability of structures. In this paper, mechanical behavior of a kind of 2D C/SiC composite was investigated at temperatures ranging from room temperature (20C) to 600C under quasi-static and dynamic uniaxial compression. The results show the composite has excellent high temperature mechanical properties at the tested temperature range. Catastrophic brittle failure is not observed for the specimens tested at different strain rates. The compressive strength of the composite deceases only 10% at 600C if compared with that at room temperature. It is proposed that the decrease of compressive strength of the 2D C/SiC composite at high temperature is influenced mainly by release of thermal residual stresses in the reinforced carbon fiber and silicon carbon matrix and oxidation of the composite in high temperature atmosphere.

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Achieving room-temperature brittle-to-ductile transition in ultrafine layered Fe-Al alloys

Science Advances ◽

10.1126/sciadv.abb6658 ◽

2020 ◽

Vol 6 (39) ◽

pp. eabb6658

Author(s):

Lu-Lu Li ◽

Yanqing Su ◽

Irene J. Beyerlein ◽

Wei-Zhong Han

Keyword(s):

Room Temperature ◽

Extreme Environments ◽

High Strength ◽

Layered Composite ◽

Al Alloys ◽

Brittle To Ductile Transition ◽

Transmission Electron ◽

Structural Applications ◽

Wear And Corrosion Resistance ◽

New Applications

Fe-Al compounds are of interest due to their combination of light weight, high strength, and wear and corrosion resistance, but new forms that are also ductile are needed for their widespread use. The challenge in developing Fe-Al compositions that are both lightweight and ductile lies in the intrinsic tradeoff between Al concentration and brittle-to-ductile transition temperature. Here, we show that a room-temperature, ductile-like response can be attained in a FeAl/FeAl2 layered composite. Transmission electron microscopy, nanomechanical testing, and ab initio calculations find a critical layer thickness on the order of 1 μm, below which the FeAl2 layer homogeneously codeforms with the FeAl layer. The FeAl2 layer undergoes a fundamental change from multimodal, contained slip to unimodal slip that is aligned and fully transmitting across the FeAl/FeAl2 interface. Lightweight Fe-Al alloys with room-temperature, ductile-like responses can inspire new applications in reactor systems and other structural applications for extreme environments.

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Fabrication and tensile properties of continuous-fiber reinforced Ni3Al–Al2O3 composites

Journal of Materials Research ◽

10.1557/jmr.1991.1673 ◽

1991 ◽

Vol 6 (8) ◽

pp. 1673-1679 ◽

Cited By ~ 37

Author(s):

J.H. Schneibel ◽

E.P. George ◽

C.G. McKamey ◽

E.K. Ohriner ◽

M.L. Santella ◽

...

Keyword(s):

Single Crystal ◽

Tensile Properties ◽

Hot Pressing ◽

Metal Matrix ◽

Room Temperature ◽

Al Alloys ◽

Matrix Composites ◽

Fiber Reinforced ◽

Continuous Fiber ◽

Crystal Fibers

Continuous-fiber reinforced metal-matrix composites consisting of Ni3Al alloys and Saphikon Al2O3 single crystal fibers were fabricated by hot-pressing of fiber-foil lay-ups. Two matrix compositions were employed, namely, IC50 (Ni–22.5Al–0.5Zr–0.1B, at. %) and IC396M (Ni–15.9Al–8.0Cr–0.5Zr–1.7Mo–0.02B, at. %). Etching of the foils in aqueous FeCl3 solution prior to lay-up and hot-pressing tended to improve fiber-matrix bonding and the density-normalized room temperature yield stress. Whereas strength improvements for the IC50 matrix were only moderate, significant improvements were found for an IC396M composite reinforced with 10 vol. % of Saphikon fibers.

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The Mechanical Behavior and Deformation Mechanisms of Nb-Al-V Alloys

MRS Proceedings ◽

10.1557/proc-460-671 ◽

1996 ◽

Vol 460 ◽

Author(s):

D. K. Tappin ◽

D. N. Horspool ◽

L. S. Smith ◽

M. Aindow

Keyword(s):

Mechanical Behavior ◽

Room Temperature ◽

Compression Testing ◽

Deformation Mechanisms ◽

Dislocation Activity ◽

Partial Dislocations ◽

Shear Transformation ◽

B2 Phase ◽

A15 Phase ◽

Phase Strains

ABSTRACTA series of Nb-Al-V alloys containing 20–40 at. % V and 10–25 at. % Al have been investigated. The phase distributions in the alloys indicate that Al promotes the formation of the A15 phase whilst V stabilises a B2 phase. Room temperature compression testing revealed that the B2 is inherently ductile such that for the alloys with less than 40% by volume of the A15 phase, strains of over 50% were obtained easily. The 2% offset yield stresses of these alloys did not vary significantly with composition, being 1.2±0.1GPa in each case. TEM studies were used to show that the deformation in the B2 phase occurs predominantly by the glide of screw-type super-partial dislocations with b=l/2<111> on {110} and {112}. In some alloys this dislocation activity was preceded by the formation of pseudo-twins, via a martensitic shear transformation.

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Ductility and Fracture Behavior of Polycrystalline Ni3Al Alloys

MRS Proceedings ◽

10.1557/proc-81-355 ◽

1986 ◽

Vol 81 ◽

Cited By ~ 10

Author(s):

C. T. Liu

Keyword(s):

Fracture Behavior ◽

Room Temperature ◽

Elevated Temperatures ◽

Grain Shape ◽

Tensile Ductility ◽

Dynamic Effect ◽

Al Alloys ◽

Gaseous Oxygen ◽

Comprehensive Review ◽

Room Temperature Ductility

AbstractThis paper provides a comprehensive review of the recent work on tensile ductility and fracture behavior of Ni3AI alloys tested at ambient and elevated temperatures. Polycrystalline Ni3Al is intrinsically brittle along grain boundaries, and the brittleness has been attributed to the large difference in valency, electronegativity, and atom size between nickel and aluminum atoms. Alloying with B, Mn, Fe, and Be significantly increases the ductility and reduces the propensity for intergranular fracture in Ni3 Al alloys. Boron is found to be most effective in improving room-temperature ductility of Ni3Al with <24.5 at. % Al.The tensile ductility of Ni3Al alloys depends strongly on test environments at elevated temperatures, with much lower ductilities observed in air than in vacuum. The loss in ductility is accompanied by a change in fracture mode from transgranular to intergranular. This embrittlement is due to a dynamic effect involving simultaneously high localized stress, elevated temperature, and gaseous oxygen. The embrittlement can be alleviated by control of grain shape or alloying with chromium additions. All the results are discussed in terms of localized stress concentration and grain-boundary cohesive strength.

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