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Elevated-temperature tensile deformation and fracture behavior of particle-reinforced PM 8009Al matrix composite

Chen Shuang, Chen Guoqiang, Gao Pingping, Liu Chunxuan, Wu Anru, Dong Lijun, Huang Zhonghua, Ouyang Chun, Zhang Hui

Bulletin of the Polish Academy of Sciences. Technical Sciences

2021

Vol. 69, nr 5

art. no. e138846

Tensile tests of 8009Al alloy reinforced with SiC and Al₂O₃ particles fabricated by powder metallurgy (PM) were conducted at temperatures of 250–350°C and strain rates of 0.001–0.1 s⁻¹. The ultimate tensile strength and yield strength of the samples decreased while the temperature and strain rate increased. The elongation slightly decreased at first and then increased with growing temperature because of the medium-temperature brittleness of the alloy matrix. When the strain rate was 0.1 s⁻¹, the elongation of the 8009Al/Al₂O₃ composites always decreased with an increase in temperature because of the poorly coordinated deformation and weak bonding between the matrix and Al₂O₃ particles at such a high strain rate. The work-hardening rates of the composites sharply increased to maxima and then decreased rapidly as the strain increased. Meanwhile, the 8009Al/SiCₚ composites displayed superior UTS, YS, elongation, and work-hardening rates than those of the 8009Al/Al₂O₃ composites under the same conditions. Compared to 8009Al alloys reinforced with spherical Al₂O₃ particle, 8009Al alloys reinforced with irregular SiC particles exhibited a better strengthening effect. The fracture mechanism of the 8009Al/SiCₚ composites was mainly ductile, while that of the 8009Al/Al₂O₃ composites was primarily debonding at the matrix–particle interfaces in a brittle mode.

CDM mechanisms-based modelling of tertiary creep: ability to predict the life of engineering components

Hayhurst D. R.

Archives of Mechanics

2005

Vol. 57, nr 2-3

103-132

The paper demonstrates how computational CDM can be used to predict the behaviour of structural components, ranging from modest stress concentrators to the growth of cracks by creep. Size effects in CDM analysis are addressed, and it is shown how a non-local CDM approach can be used to predict the observed crack tip behaviour. The proviso being that the length scales, associated with the damage fields and gradients, be modelled to comply with continuum theory. It is shown how damage state variable theories may be used to provide traceability from the physics of micro-mechanisms to the macro-material behaviour described by constitutive equations. The paper presents a detailed analysis of creep rupture in ferritic steel weldments, and shows how multi-axial stress rupture criteria, weldment phase dimensions, and constitutive equations for each material phase of the weld, can be used in Finite Element CDM analyses to predict the results of experiments carried out on butt-welded pipes and cross-welded tension testpieces. Original results are presented which show how the above CDM techniques have been used to perform a three-dimensional CDM high-temperature creep rupture analysis of a welded cylinder-cylinder pressure vessel intersection; and, to predict damage initiation and crack growth. The paper also demonstrates how CDM conservatively predicts the vessel lifetime; and, how the experimentally observed weld failure mechanism is well predicted.