Abstract: There are provided a process for forming a silicon nitride sintered body, encompassing a sialon sintered body, by making much of the superplasticity of the sintered body intact as a simple material without formation thereof into a composite material, and a formed sintered body produced by the foregoing process. A silicon nitride sintered body (encompassing a sialon sintered body) having a relative density of at least 95% and a linear density of 120 to 250 in terms of the number of grains per 50 .mu.m in length in a two-dimensional cross section of the sintered body is formed through plastic deformation thereof at a strain rate of at most 10.sup.-1 /sec under a tensile or compressive pressure at a temperature of 1,300 to 1,700.degree. C. The formed sintered body has a degree of orientation of 5 to 80% as examined according to a method specified by Saltykov, a linear density of 80 to 200, and excellent mechanical properties especially at ordinary temperatures.

Abstract: There are disclosed in process for shaping ceramic composites which comprises shaping a sintered silicon nitride-silicon carbide composite material having a microstructure formed predominantly of equiaxed grains with an average grain size of 2 .mu.m or below and a silicon carbide content of 10-50% by volume, obtained by liquid-phase sintering, at least 40% by volume of the silicon nitride in the material being in the .beta.-phase, by superplastically deforming said material at a strain rate of 10.sup.-6 sec.sup.-1 to 10.sup.-1 sec.sup.-1 under application of tensile stress or compressive stress in a superplastic temperature region of 1400.degree.-1700.degree. C., and a process for shaping ceramic composites which comprises shaping said sintered composite material by superplastic deformation as described above and then heat-treating the shaped article obtained in a non-oxidizing atmosphere under normal or applied pressure at 1000.degree.-2300.degree. C.

Abstract: A living hard tissue replacement is prepared by subjecting a calcium phosphate base ceramic material to superplastic forming. Also provided is a method for preparing a composite body comprising the step of joining a cover of a calcium phosphate base ceramic material to a substrate of a heterogeneous material by superplastic forming. Superplastic forming is often performed by hot isostatic pressing. The living hard tissue replacement and composite body are useful as artificial dental roots, dental crowns, and bones.

Abstract: A shaped article of superplastic ceramic composed of zirconia toughened ceramic containing, or not containing, fine alumina powder is produced by deforming the ceramic under the action of stress at a temperature in the range of superplastic temperatures thereof.

Abstract: A method for plastic working of ceramics comprising the steps of causing a sintered or pre-sintered body of polycrystalline ceramics containing at 20.degree. C. tetragonal-phase zirconia crystals to undergo plastic deformation at a temperature of about 1,000.degree. C. to about 1,600.degree. C. and then heating the ceramics body at a temperature of about 1,300.degree. C. to about 1,650.degree. C.