Surface deformation of sapphire crystal

R. Nowak, T. Sekino, K. Niihara

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The anisotropic surface deformation of sapphire has been studied by means of depth-sensing indentation experiments with a small-radius spherical indenter loaded onto the basal (0001) and the prismatic () planes of the crystal. The results of the low-speed high-accuracy continuous-indentation test have revealed significant differences in the mechanical behaviour of alumina crystals when indented on different crystallographic planes. A special effort has been made to clarify the origin of the characteristic discontinuities appearing in the loading part of the indentation hysteresis loops observed for the experiments performed on the (0001) as well as () planes of sapphire. It was concluded that the large 'step-in' reflects the formation of a twin in g-alumina crystals deformed with a blunt indenter. A new resolved shear stress model has been pro-posed in order to meet the requirements of spherical indentation. The results of numerical calculations predicted the deformation systems activated in the vicinity of spherical indentation. The prediction correlated with the observations of residual impressions.

Original languageEnglish
Pages (from-to)171-194
Number of pages24
JournalPhilosophical Magazine A
Volume74
Issue number1
DOIs
Publication statusPublished - 1996
MoE publication typeA1 Journal article-refereed

Keywords

  • SPHERICAL INDENTERS
  • BRITTLE MATERIALS
  • ENERGY PRINCIPLE
  • SINGLE-CRYSTALS
  • INDENTATION
  • HARDNESS
  • ALPHA-AL2O3
  • ALUMINA
  • SLIP
  • ANISOTROPY

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