Mechanical high-temperature properties and damage behaviour of refractory composites

粗晶耐火复合材料由于其在烧结过程中的低收缩、高温下的塑性和导电性而在混合结构中具有很高的应用潜力，例如在可加热的热屏蔽件中或作为铸钢件的塞。子项目3的目的是在第二个供资期内调查研究小组内产生的复合材料和模型材料复合材料（混合隔热屏和混合塞）的机械性能和损伤行为，这些复合材料和模型材料复合材料以粗粒Al 2 O3作为外壳，以粗粒金属陶瓷复合材料（60% Nb或Ta和40% Al 2 O3）作为高温下的电加热芯。将在与应用相关的温度范围内研究材料复合材料（i）粗颗粒Al 2 O3和复合材料（ii）来自注浆成型工艺、（iii）来自藻酸盐途径的颗粒和（iv）来自增材制造的颗粒以及混合复合材料的各个组分的高温性能，例如抗压强度、蠕变和应力松弛行为。此外，将研究循环冷等静压（不同压力和压力脉动）和随后的烧结制度（1600°C，1700°C）对具有子项目1中不同预合成颗粒的复合材料在高达1600°C的温度下的机械性能和损伤行为的影响。使用与夹层结构相同的复合颗粒。感兴趣的是多孔复合材料的机械性能与子项目6中通过FAST烧结的样品的比较，其具有低得多或可忽略不计的孔隙率。此外，重点是断裂力学性能。特别感兴趣的是在陶瓷/复合材料界面的夹层结构中的损伤行为。4-对有缺口和无缺口试样的点弯曲试验将用于研究金属陶瓷芯和粗晶粒Al 2 O3包层的损伤行为。除了声发射测量外，还将对夹层结构进行热成像调查，以检测夹层结构在加热和机械载荷期间陶瓷覆层的损伤发展。

Coarse-grained refractory composites have a high potential for applications in hybrid construction, such as in heatable heat shields or as plugs for steel casting due to their low shrinkage during sintering, plasticity at high temperatures and electrical conductivity. The aim of subproject 3 is to investigate in the second funding period the mechanical properties and damage behaviour of the composites and model material composites (hybrid heat shields and hybrid plugs) generated within the research group based on coarse-grained Al2O3 as outer shell and coarse-grained metal-ceramic composites (60% Nb or Ta and 40% Al2O3) as electrically heatable core at high temperatures. The high-temperature properties such as compressive strength, creep and stress relaxation behaviour of the individual components of the material composites (i) coarse-grained Al2O3 and the composites (ii) from the slip casting process, (iii) from granules of the alginate route and (iv) from additively manufactured granules, as well as of the hybrid composite are to be researched in the temperature range relevant to the application. In addition, the influence of cyclic cold isostatic pressing (different pressures and pressure pulsations) and subsequent sintering regimes (1600°C, 1700°C) on the mechanical properties and damage behaviour of the composites with different pre-synthesized grains from subproject 1 at temperatures up to 1600°C will be investigated. The same composite granules are used as for the sandwich structures. Of interest is also the comparison of the mechanical properties of the porous composites with the samples sintered in subproject 6 by means of FAST, which have a much lower or negligible porosity. In addition, the focus is on the fracture mechanical properties. Of particular interest is also the damage behaviour at the ceramic/composite interface in the sandwich structure. 4-point bending tests on notched and unnotched specimens will be used to investigate the damage behaviour of the metal-ceramic core and the coarse-grained Al2O3 cladding. In addition to the acoustic emission measurements, a thermographic investigation will also be applied to the sandwich structures to detect the damage development in the ceramic cladding of the sandwich structures during heating and mechanical loading.