Ceramics based on zirconia are finding increasing use as materials in various areas of technology, and in medicine. As a result more attention is being paid to improving and investigating such products in many developed countries [i, 2, etc.], including the USSR where the problem has been dealt with in Ogneupory [3, enc.], Problemy Prochnosti [4], and a number of other articles.However, in almost all the articles that have presented data on the mechanical behavior of zirconia, somewhat limited data is given, since normally complex studies have not been carried out, although such results would yield valid (especially comparative) all-round information on the ceramic; this enables us to assess with confidence the expected working capacity and form general ideas on the actual behavior under load.One reason for the above situation is the fact that complex investigations require a sufficient number of identical specimens which it is impossible to obtain in an industry which does not possess a good production control procedure for ceramics. Such investigations also require standard testing equipment (preferably concentrated in one place) which will facilitate the production of various test parameters that show low measurement errors. These conditions were observed in the present work in which we selected zirconia ceramics that had proved themselves in practice, and in previous research [5]; these were partially stabilized with magnesium oxide. It was used by Nilcra Ceramics Pty. Ltd (Australia) to prepare ball valves for the chemical and petroleum industries, also components in experimental diesel engines, artificial dentures, etc. (Fig. I). A feature of this ceramic is that it passes through additional technical processing, depending on its purpose (like steel).In our investigations we concentrated on TS-grade ceramic (subsequently referred to as Mg-ChSTs) designed for working in thermal conditions. Dies, for example, and other components for high-temperature drawing of copper wire were made from it.Plate-like blanks were obtained by using a method in which 3% MgO (mass) was added to the starting powder. Then it was ballmilled (grinding medium made of ZrO 2) in distilled water to an average particle size of 1-3 pm. Then the powder was dried in a stream of heated air. The blanks were preformed by dry pressing with synthetic plasticizer, and then hydrostatically pressed at 200 MPa. They were fired in a furnace heated with gas at 1700~ Af-

No abstract