Journal of the American Ceramic Sociery-Ma er al Vol. 87. No. 3 Table I. Phase Content of 9, 4Mg-/ at 5.2 MPa (4) Structural and Microstructural Effects Determined by Neutron Diffraction In addition to phase quantification, the in situ neutron diffrac z M(amu) V(A') wt ErTwt tion and Rietveld analysis gives data on changes to the structure and microstructure of the ceramic during loading and un 4I1.61131.520.5 9 particular, changes were noted in the axial ratio, c/a, of the 2123.2267.0412.162.61 tetragonal phase, preferred orientation in the tetragonal and mon m-Zr( 4123.22139.660.36.50.7 aclinic phases, and the internal strain distribution in the tetragonal Mg2Zr3O123696.72679060.0492180.9 phase. A composite diagram summarizing these results is shown in (A) Tetragonality: The c/a ratio of the tetragonal phase >1000 MPa(Fig 4(b). Likewise, when the load was between 0 adopting the pseudocubic unit cell, is shown in Fig. 5(a). Overall c/a increases as a function of applied stress and the slopes of the within one standard deviation(Fig. 4(a)). in good correspondence curves during loading and unloading are the same at stresses with the weight fraction of monoclinic phase. The amount of <1100 MPa. The lattice parameters observed were the average phase began to decrease after the load reached 800 MPa, and the alues of those crystallites oriented so as to satisfy Braggs law. So rate accelerated after the stress exceeded 1 100 MPa In agreement from-0-1 100 MPa, tetragonal particles with c axes perpendicu- with the strain gauge data, the critical stress for the stress-induced lar to the applied stress expanded(Poisson strains) faster than transformation would appear to be-1000 MPa in this material those with the a axes perpendicular to the applied stress or more These results confirm that the f-m phase transformation is responsible for the bulk of the strains observed In the unloading half of the stress cycle, the fraction of monoclinic phase did not stop increasing, but rose quickly until 1.0215 1000 MPa. Between 1000 MPa and 0 MPa. the fraction of monoclinic phase continued to increase but at a much smaller rate. The apparent tetragonal phase content too continued to decrease ith a stable rate during unloading 1.0210 From the observations shown in Figs. 4 (a) and(b). it was estimated that in the loading half cycle (i.e, <1225 MPa). the tetragonal phase decreased 10.9=1, 2 wt% and the monoclinic the tetragonal phase was 190+1.5 wt% and total increase in the o10205 hase increased 12.2+ lI wt%. The total estimated decrease in monoclinic phase was 16.9+ 1. I wt%. 1.0200 0.35 0.20 1.04 Applied stress(MPa) 1200 Applied stress(MPa) a)Tetragonal-phase content in 9.4Mg-PSZ during a compression loading cycle calculated from Rietveld refinement scale factors: Fig. 5. (a) Tetragonality of the I phase: (b) internal strain distribution in rved monoclinic-phase content during the same the loading. I phase; (c) March coefficient of t phase, during loading and unloading of cycle. Error bars indicate one estimated standard deviation. 9.4Mg-PSZ. Error bars indicate one estimated standard deviation