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Creep of heat treated silicon nitride with neodymium and yttrium oxides additions

机译：掺有钕和钇氧化物的热处理氮化硅的蠕变

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摘要

At the present work, samples of silicon nitride with 12 wt% of yttriumeodymium oxides mixture were formed by gas-pressure sintering. Pos sintering heat treatments in nitrogen with a stepwise temperature variation were performed in some samples. The short term compressive creep tests were undertaken in an argon atmosphere, over a stress range of 50-300 MPa and temperature range of 1200-1400℃ Values of stress exponents near unity for (ⅰ) low temperature testing in all materials and (ⅱ) all temperatures for heat treated samples suggest diffusion accommodation processes, involving ambipolar diffusion of ionic species in the grain boundary phases. Crystallization of the remnant phase during heat treatment in a nitrogen atmosphere gives rise to further formation of new phases in the Nd-Si-O-N system such as Nd_4Si_3O_(12) and Nd_2Si_3O_3N_4. A consequence of this crystallization is a significant reduction in stress exponents and creep rates for the heat treated samples. The wedge crack observed after creep testing at specimens in its as-sintered condition may be related to the increased probability of cavitation in the second phase glassy layers at triple point junction.
机译：在目前的工作中，通过气压烧结形成了具有12wt％的钇/钕氧化物混合物的氮化硅样品。在一些样品中在氮气中进行逐步烧结的正烧结热处理。短期压缩蠕变试验是在氩气氛中进行的，其应力范围为50-300 MPa，温度范围为1200-1400℃。（ⅰ）所有材料的低温测试和（ⅱ）的应力指数值接近于1。热处理样品的所有温度均表明存在扩散适应过程，涉及晶界相中离子物质的双极扩散。在氮气氛中热处理期间残留相的结晶导致在Nd-Si-O-N系统中进一步形成新相，例如Nd_4Si_3O_（12）和Nd_2Si_3O_3N_4。这种结晶的结果是大大降低了热处理样品的应力指数和蠕变速率。在烧结状态下的蠕变试验后，在试样经蠕变试验后观察到的楔形裂纹可能与三点接合处第二相玻璃层中空化的可能性增加有关。

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