SUPERPLASTIC FLOW IN A NONSTOICHIOMETRIC CERAMIC - MAGNESIUM ALUMINATE SPINEL

被引:21
作者
LAPPALAINEN, R
PANNIKKAT, A
RAJ, R
机构
[1] Department of Materials Science and Engineering, Cornell University, Ithaca
来源
ACTA METALLURGICA ET MATERIALIA | 1993年 / 41卷 / 04期
基金
美国国家科学基金会;
关键词
D O I
10.1016/0956-7151(93)90172-O
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Tensile superplastic deformation of ceramics is often limited by their susceptibility to intergranular cavitation. However, we find that fine grained magnesium aluminate spinel exhibits unusual superplastic ductility at strain rates of up to 5 x 10(-4)s-1 and at temperatures below 1280-degrees-C. The ductility is all the more remarkable because the flow stress of the spinel was in the range of several hundred MPa. We propose that the unusual cavitation resistance of interfaces in spinel is related to its non-stoichiometry. We further propose that the non-linear threshold stress like rheology which we have measured is related to an electrical double (barrier) layer which is postulated to form to compensate the net charge at interfaces of non-stoichiometric ceramics. We estimate that a boundary double layer potential, psi(b), of 5-50 mV can account for this threshold stress. The phenomenological characteristics of superplastic flow in the spinet are shared by other non-stoichiometric ceramics such as yttria stabilized zirconia, hydroxyapatite and zinc sulphide.
引用
收藏
页码:1229 / 1235
页数:7
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