High temperature plastic deformation of a tetragonal Y2O3-stabilized ZrO2 single crystals
High temperature plastic deformation of a tetragonal Y2O3-stabilized ZrO2 single crystals
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四方 Y2O3 稳定 ZrO2 单晶的高温塑性变形
DOI：
10.1016/s1359-6462(01)00934-4
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发表时间：
2001
影响因子：
6
通讯作者：
A. Domínguez
中科院分区：
文献类型：
--
作者：
A. Muñoz;F. Wakai;A. Domínguez
自从在氧化锆-氧化钙体系中发现相变增韧[1]以来，氧化锆基陶瓷已经成为陶瓷材料科学技术领域中的决定性参考材料。由于其在低温下具有优异的强度和韧性，这些努力主要集中在MgO-ZrO2系统上。这些特性可以用应力诱导的马氏体相从四方相向单相转变来解释。在不同的稳定剂中，Y_2O_3可能是最有前途的高温氧化锆基陶瓷添加剂。这一事实是基于可以发展的相和微观结构的丰富性。当Y_2O_3含量高于9mol%时，可以完全稳定单立方相中的ZrO_2。在这个区域，Y2O3完全稳定的ZrO2(Y-FSZ)表现出强烈的固溶体增强作用，当溶质含量从9.4%增加到21mol%时，在1400℃时，流动应力从150增加到360 Mpa，容易滑动取向[3]。当温度高于1550℃时，这些单晶以回复蠕变变形，为位错攀升速率控制机制[3]。当Y_2O_3含量减少(低于9mol%)时，只要合金从c轴上方快速冷却，就会形成伪立方t相。这种亚稳相在低溶质含量(2摩尔%)、四方相(T)和富溶质立方相中扩散分解。这些t相具有明确的内部显微组织，由片层(每个片层都是一个四方变体)组成，其中相邻变体的c轴旋转90，并具有{110}习惯面，指的是母体立方相[4]。这些析出物的微观结构非常有效地减小了析出过程中的相干应变。这种机制允许沉淀物生长，保持了共格和稳定性，而不会转变为单斜晶系。这种两相材料具有很强的高温析出硬化作用，当单晶在1600℃下保温150h时，对于4.5mol%Y_2O_3-ZrO_2，在1400℃下的流动应力为550 Mpa，并且形成了清晰的析出物长度在1~3m之间的显微组织[5]。
Since the discovery of the transformation toughening in the ZrO2-CaO system [1], zirconia-based ceramics have became a decisive reference in the challenging world of the science and technology of ceramics materials. These efforts have mainly been focused on the MgO-ZrO2 system due to its excellent properties of strength and toughness at low temperatures. These properties are explained by the stress-induced martensitic transformation from the tetragonal to the monoclic phase. A good review paper on these phenomena can be found in [2].Among the different additives to stabilize ZrO2 (MgO, CaO, Y2O3,...), Y2O3,(giving rise to the ZrO2-Y2O3 system) is probably the most promising one in zirconia-based ceramics for high temperature applications. This fact is based upon the richness of phases and microstructures which can be developed. It is possible to fully stabilize ZrO2 in the single cubic phase when the Y2O3 content is higher than 9 mol%. In this domain, the Y2O3 fully stabilized ZrO2 (Y-FSZ) shows a potent solid solution strengthening with an increase in the flows stress from 150 to 360 MPa at 1400 C when the solute content increases from 9.4 to 21 mol% for the easy glide orientation [3]. At temperatures higher than 1550 C, these single crystals deform by recovery creep, being dislocation climb the rate-controlling mechanism [3]. When the Y2O3 content decreases (below 9 mol%), a pseudocubic t phase is formed as long as the alloys are rapidly cooled from above the c solvus. This metastable phase decomposes diffusionally in a low solute content (2 mol%) tetragonal precipitate (t) and a solute-rich cubic matrix. These t precipitates have a well-defined internal microstructure, composed of lamellas (each of them is a tetragonal variant), in which the c-axes of adjacent variants are rotated by 90 and having a {110} habit plane, referring to the parent cubic phase [4]. The microstructure of these precipitates is very efficient to minimize coherence strains during precipitation. This mechanism allows precipitates to grow retaining coherency and stability without transforming to monoclinic. This two-phase material shows a potent high temperature precipitation hardening with a flow stress at 1400 C of 550 MPa for a 4.5 mol% Y2O3-ZrO2 when the single crystals are annealed at 1600 C for 150 h and a well-defined microstructure with precipitates length between 1 and 3 m are developed [5].