Facility for preparation of advanced metallic and ceramic materials

虽然用粉末制备先进陶瓷及其复合材料已经有几十年的历史了，但现在人们对从粉末来源生产金属部件的兴趣越来越大。与更传统的金属成形方法(如铸造)相比，这种方法提供了近净成形和减少材料损耗的好处。先进颗粒材料的加工要求粉末在通过烧结最终致密化之前首先被固化成所需的形状。有时，这可以通过简单的单轴压缩实现，特别是对于选定的金属合金，如铝和钢(使用高达600兆帕的压力)，以及当颗粒尺寸中等粗大(即&gt；40微米)时。然而，对于镁和钛这样的金属，它们可以通过孪生变形，即使在中等的单轴压力下(即&gt；100兆帕)，模具粘合也成为一个严重的问题。此外，使用细小的金属粉末(即20微米)根本不可行，即使这种粉末可能具有更大的“烧结性”。同样，对于微米或亚微米尺寸的陶瓷粉末，通常需要使用高压等静压成型。单轴压制的陶瓷预制件没有足够的生坯强度或密度，因为它们总是不能在超过~50兆帕的压力下压制，因为可能会产生模具粘结和磨损。这些问题可以通过冷等静压(CIP)得到缓解，尤其是在低压单轴挤压之后。本提案要求为能够承受高达689兆帕压力的CIP系统提供资金，该系统将用于铝、镁、镍和钛合金以及先进的结构陶瓷，如氮化硅和碳化钛。CIP将允许生产新型的陶瓷增强金属基复合材料，其中细颗粒尺寸可以用来促进微观结构的均质性。还提供了气氛可控的手套箱，因此可以压制更多的活性金属粉末，而不会暴露在氧化气氛中，这是实现更细颗粒尺寸的主要问题。最后，精密的数控铣削设备可用于CIPed预制件的进一步成形。

While advanced ceramics and their composites have been prepared from powders for many decades, there is now a growing interest in producing metallic components from powder sources. This approach offers the benefit of near-net shape production and reduced material wastage, when compared to more conventional metal forming routes such as casting. The processing of advanced particulate materials requires that the powders are initially consolidated into the desired shape, prior to final densification by sintering. Occasionally this can be achieved through simple uniaxial compression, especially for selected metallic alloys such as aluminium and steels (using pressures up to 600 MPa), and when the particle sizes are moderately coarse (i.e. > 40 microns). However, for metals such as magnesium and titanium, which can deform by twinning, die binding becomes a serious problem even at moderate uniaxial pressures (i.e. > 100 MPa). In addition, the use of fine metallic powders (i.e. < 20 microns) is simply not feasible, even though such powders would have potentially greater 'sinterability'. Similarly, for micron or sub-micron sized ceramic powders it is generally necessary to use high pressure isostatic compaction. Uniaxially pressed ceramic preforms do not have sufficient green strength or density, as they invariably cannot be pressed at pressures above ~50 MPa, as die binding and wear can arise. These problems can be alleviated by cold isostatic pressing (CIP), especially when following low pressure uniaxial pressing. The present proposal requests the provision of funding for a CIP system, capable of pressures up to 689 MPa, which will be used for alloys based on aluminium, magnesium, nickel and titanium, as well as for advanced structural ceramics, such as silicon nitride and titanium carbide. The CIP will allow production of novel, ceramic-reinforced metal matrix composites, where fine particle sizes can be used to promote microstructural homogeneity. An atmosphere controlled glove-box is also available, so that more reactive metal powders can be pressed without exposure to an oxidising atmosphere, which is a major problem for finer particle sizes. Finally, precision CNC milling facilities are available for further shaping of CIPed preforms.