On the Origin of the Enhanced Creep Resistance in Underaged Al-Cu Based Alloys

Hutchinson, Christopher R.; Cornall, P.; Gouné, M.

doi:10.4028/www.scientific.net/MSF.519-521.1029

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HomeMaterials Science ForumAluminium Alloys 2006 - ICAA10On the Origin of the Enhanced Creep Resistance in...

On the Origin of the Enhanced Creep Resistance in Underaged Al-Cu Based Alloys

Abstract:

It has recently been observed that the creep resistance of Al-Cu based precipitation hardened alloys may be enhanced through use of the underaged temper. We have treated this problem theoretically by considering the motion of a dislocation through a precipitation hardened structure and discuss the physical origin of the enhanced creep resistance in the underaged condition. The variation in expected creep resistance as a function of aging treatment is calculated and the possible generality of the experimental observations is considered.

Info:

Periodical:

Materials Science Forum (Volumes 519-521)

Main Theme:

Aluminium Alloys 2006 - ICAA10

Edited by:

W.J. Poole, M.A. Wells and D.J. Lloyd

Pages:

1029-1034

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.519-521.1029

Citation:

C. R. Hutchinson et al., "On the Origin of the Enhanced Creep Resistance in Underaged Al-Cu Based Alloys", Materials Science Forum, Vols. 519-521, pp. 1029-1034, 2006

Online since:

July 2006

Authors:

Christopher R. Hutchinson, P. Cornall, M. Gouné

Keywords:

Age Hardening, Creep, Modeling

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References

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Paper TitlePages

A Microscopic Mechanics Model for Thermal Fatigue Crack Growth

Authors: Yi Sun, Rui Zhang, Jun Ma

205

Creep Resistance of Zr-Sn-Nb-Fe-Cr Alloy

Authors: Zhongkui Li, Wen Sheng Wang, J.J. Zhang, Lian Zhou

Abstract: The creep resistance of one kind of Zirconium based alloy with Niobium, Iron, Chromium , Tin alloying elements was investigated, the creep curve ( e-t) was obtained in stress levels of 117MPa 、137MPa、157MPa respectively by holding 200 hours at 400°C. The results show that the creep resistance of this alloy is much better than that of Zircaloy-4. The microstructure of post- creep test was observed by TEM, which shows that the dislocation morphology is changed from dislocation lines to dislocation cells with strain increasing , and some precipitates grow larger. It is concluded that the creep is controlled by dislocation climb-glide diffusion mechanism.

1405

Influence of Solute Content and Secondary Phases on the Nano-Creep Behavior of Mg-Al-Ca Alloys

Authors: Li Hong Han, Derek O. Northwood, Henry Hu

Abstract: Mg-Al-Ca alloys with 1wt.% and 2 wt.% Ca additions (AC51 and AC52) were cast by the Permanent Mold technique. The microstructures of the as-cast Mg-Al-Ca alloys were observed by SEM with EDS analysis. The secondary phases were mainly precipitated along the grain boundaries and exhibited a continuous network microstructure for the AC52 alloy and a divorced microstructure for the AC51 alloy. EDS microanalysis showed that the solute (Ca) content in the grains of the AC52 alloy is higher than that in the AC51. A three-sided pyramidal (Berkovich) diamond indenter was used to characterize the local nano-creep behavior at room temperature within the α-Mg in grains. The nano-creep results showed that the AC52 alloy has better creep resistance than the AC51 alloy at all loads at room temperature. The creep exponent n, obtained from the indentation creep data, changes from 6.3 to 3.0 for AC51 alloy and from 6.6 to 3.2 for AC52 alloy at a critical stress (132 MPa for the AC51 and 145 MPa for the AC52). The transition in creep behavior at higher stresses is associated with a change in the deformation mechanisms.

605

Solute Partitioning to Enhance Mechanical Properties of Aged Aluminium Alloys

Authors: Ian J. Polmear, Roger N. Lumley

Abstract: Deliberate partitioning of solute elements between the matrix solid solution and dispersed precipitates in aged aluminium alloys can be facilitated by underageing during heat treatment. Although this practice may cause some reduction in tensile properties, it has been shown that significant improvements may be achieved in creep resistance, fatigue strength and fracture toughness. Exploitation of secondary precipitation can allow simultaneous increases to be obtained in tensile and fracture properties.

487

The Role of Interfacial Precipitates on Creep Behaviour of Power Metallurgy (PM) Ti-48Al-2Cr-2Nb+1W Alloy

Authors: Dong Yi Seo, Scott Bulmer, H. Saari, Han Liang Zhu, Peter Au

Abstract: Pre-alloyed powders with a nominal composition of Ti-48Al-2Cr-2Nb+1W were consolidated by hot isostatic pressing (HIP). After the HIP process, a step cooled heat treatment (SCHT) with a carefully controlled cooling rate was applied to homogenize the HIP’ed microstructure and produce a fully lamellar microstructure. Following the SCHT, various isothermal aging at 950 °C and step aging processes form interfacial precipitates at the lamellar interfaces. The morphology, size, and distribution of the precipitates are dependent on the aging condition. Creep tests were carried out in air at 760 °C and 276 MPa to investigate the effect of interfacial precipitates. Primary creep resistance and creep life of the 8 and 144 hr aged conditions are improved substantially compared to the unaged condition due to the existence of the interfacial precipitates. However, the step aging process improves the creep resistance only slightly, probably because of the size and distribution differences of the interfacial precipitates compared to the 144 hr aged condition. Microstructure control is important since it has a substantial influence on creep behavior, especially primary creep resistance.

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