Evaluation of Zr- and Ti-containing Aluminum-Boron Carbide composites as materials for elevated temperature performance in engineering applications

汽车、航空航天和其他行业对提高关键部件性能的持续需求一直是改进的高性能结构材料发展的驱动力。金属基复合材料(MMCs)是一类很有前途的新型材料。两种常用的金属基质是铝和钛，它们密度低，有多种合金形式可供选择。然而，钛合金的高成本限制了它们在那些以性能为主要目标的情况下的应用，而不考虑成本。添加到复合材料中的增强剂是碳化物、氧化物和氮化物，因为它们在常温和高温下具有优异的比强度和硬度组合。铝金属基复合材料不仅重量轻，而且通过增强了强度、硬度和耐磨性。虽然碳化硅和氧化铝是更常用的增强材料，但最近推出的B4C是这三种材料中最轻和最硬的，相对于当今工业中普遍存在的减轻重量标准，它是一个可行的选择。Al-B4C复合材料增强的高温强度和良好的中子吸收特性是研究其在当前和新兴应用中的适用性的有力证据。对于任何已开发产品的成功商业化，成本效益和可负担性都是需要考虑的重要因素。考虑到这一点，基于申请人在碳化硅和三氧化二铝颗粒增强铝金属基复合材料研究方面的广泛专业知识，以及最近在含锆、钛和钪的铝合金行为研究中获得的经验，拟议的研究旨在研究含锆和钛的铝B4C基金属基复合材料在需要稳定高温性能的工程应用中的潜在应用。一系列Al-B4C复合合金将以a)纯Al和b)6061合金为基体，添加钛和锆，采用熔融金属加工工艺；选择6061合金是为了评估将这些材料轧制成用于汽车车身等应用的板材的可行性。该技术由申请人于1990年发明并成功应用。这些复合材料在不同熔体温度下的流动性将通过增强体和基质之间的界面反应(即润湿性)来表征和分析，使用广泛的透射电子显微镜。利用透射电子显微镜监测热处理样品中的析出行为，研究其高温性能，以观察纳米强化Al-Zr/Ti析出物。其他重要的性能，如硬度和冲击韧性，也将被研究，以完整地表征这些材料。所获得的实验数据将为模拟此类复合材料的微结构/性能关系提供有价值的输入。这项工作的一个同样重要的组成部分将是培训这一专门研究领域的高素质人员。该项目产生的数据的基本、科学和技术方面将影响学术和工业部门，从而影响加拿大经济。

The constant need to enhance the performance of critical components used in the automotive, aerospace and other industries has been the driving force behind the development of improved high-performance structural materials. Metal matrix composites (MMCs) have emerged as a promising group of materials for such applications. Two commonly used metal matrices are those of Al and Ti, which have low densities and are available in a variety of alloy forms. However, the high cost of Ti alloys limits their application to those cases where performance is the main goal irrespective of cost. The reinforcements added to produce the composite are carbides, oxides and nitrides, selected for their excellent combinations of specific strength and stiffness at ambient and elevated temperatures. Aluminum MMCs provide both light weight, courtesy of the Al matrix, and enhanced strength, stiffness and wear resistance through the reinforcement. While SiC and Al2O3 have been more commonly used as the reinforcement, the more recently introduced B4C is both the lightest and the hardest of the three, making it a viable choice with respect to the reduced weight criterion so prevalent in today's industry. The enhanced elevated-temperature strength and favorable neutron absorption characteristics of Al-B4C composites are strong points which justify investigating their suitability for use in both current and emerging applications. For successful commercialization of any developed product, cost-effectiveness and affordability are important factors to consider. Keeping this point in mind, and based on the applicant's extensive expertise in the study of SiC and Al2O3 particulate-reinforced Al MMCs, together with experience gained from recent studies on the behavior of Al alloys containing Zr, Ti and Sc additions, the proposed study aims to investigate Al-B4C MMCs containing Zr and Ti additions as potential materials for use in engineering applications requiring stable high temperature performance. A range of Al-B4C composite alloys will be prepared using a) pure Al and b) 6061 alloy as the matrix, with Ti and Zr additions, employing the molten metal processing route; the 6061 alloy was selected for evaluating the feasibility of rolling these materials into sheets for use in car body applications, etc. A powder injection technique will be used to inject the reinforcement particulate into the molten metal. This technique was invented and successfully applied by the applicant in 1990. The fluidity of these composites at various melt temperatures will be characterized and analyzed in terms of the interfacial reactions (i.e. wettability) between reinforcement and matrix, using extensive transmission electron microscopy. The high temperature performance will be studied by monitoring the precipitation behavior in heat-treated samples using TEM for examining the nano-sized strengthening Al-Zr/Ti precipitates. Other important properties, such as hardness and impact toughness, will also be investigated for a complete characterization of these materials. The experimental data obtained will provide valuable input for modeling the microstructure/property relations in such composite materials. An equally important component of this undertaking will be the training of high qualified personnel in this specialized area of research. The fundamental, scientific and technological aspects of data generated by this project will impact both academic and industrial sectors and thereby the Canadian economy as a result.