Ryo Yamazaki; Yoshio Sakka;Kiyoshi Itatani; Koji Morita
Abstract
The effect of the granulation of starting powder on the superplasticity of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) specimen was examined; the tensile elongation of specimen at high temperature was measured in order to evaluate the superplastic deformation. The translucent ceramics were fabricated using ...
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The effect of the granulation of starting powder on the superplasticity of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) specimen was examined; the tensile elongation of specimen at high temperature was measured in order to evaluate the superplastic deformation. The translucent ceramics were fabricated using HAp powders with and without granulate (HAp and g-HAp) through the pulse current pressure sintering at 1000 ºC for 10 min: the mean grain sizes in both cases were approximately 0.2 mm. The tensile elongation of g-HAp specimen at 1000 ºC was 289 % (strain rate: 1.2 × 10 -3 s -1 ). The tensile stress was always lower than 30 MPa with maximum stress of 28.3 MPa, in contrast to the case of HAp specimen showing the maximum stress of 75.3 MPa (tensile elongation: 344 %). The lower stress of g-HAp specimen, compared to the case of HAp specimen, indicated the weak bonding of grains, but the failure being occurred by the concentrated stress at the strong bonding sites.
Abstract
Superplastic deformation behaviors of a relatively coarse-grained AZ80 magnesium alloy sheet have been investigated at temperature ranging from 350 to 430 °C and at the strain rates ranging from 1.31 × 10 -4 to 1.31 × 10 -2 s -1 by uniaxial tensile tests. Superplasticity with the maximum ...
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Superplastic deformation behaviors of a relatively coarse-grained AZ80 magnesium alloy sheet have been investigated at temperature ranging from 350 to 430 °C and at the strain rates ranging from 1.31 × 10 -4 to 1.31 × 10 -2 s -1 by uniaxial tensile tests. Superplasticity with the maximum elongation to failure of 239% was obtained at 430 °C and the strain rate of 6.56 × 10 -4 s -1 and its strain rate sensitivity exponent, the value of m is high up to 0.49. Fine interior dynamic recrystallized (DRX) grains distributed along primary grains were observed during superplastic deformation, but primary grains were not found significantly grown up. In addition, micro-cavities and their coalescences were also observed in the superplastic deformation of the relatively coarse-grained AZ80 magnesium alloy sheet. Grain boundary sliding (GBS) was considered to be the main deformation mechanism during the superplastic deformation. Dislocation creep controlled by atom diffusion through interior DRX and primary grains is suggested mainly to accommodate the GBS in superplastic deformation. Copyright © 2011 VBRI press.
