Acquisition of a Nanoindenter

9803045 Lavernia该奖项为收购纳米压头提供支持，以满足加州大学欧文分校几个正在进行的以及未来涉及纳米晶体材料的合成-结构-性能研究的研究计划的研究需要。纳米晶材料为材料科学家/工程师提供了独特的机会，以实现在其他情况下无法用平衡材料实现的性能组合。例如，据报道，纳米相陶瓷表现出异常高的延展性，而纳米相金属则表现出超高的硬度值。为此，本文提出的研究计划的目标是调查纳米晶材料的机械性能的各个方面，包括加州大学欧文分校生产的粉末、涂层和大块样品。更具体地说，研究计划将调查：1)各种金属、陶瓷和金属陶瓷在球磨过程中的显微硬度随颗粒尺寸的变化，2)热喷涂纳米晶涂层中显微硬度深度分布的实验研究，作为颗粒尺寸、孔隙率和第二相分散体(取决于冷却速度和涂层厚度)的函数，3)杨氏模量行为(取决于各种纳米晶材料的颗粒尺寸和孔隙率)，特别是在小尺寸中存在的那些，4)具有低孔隙率的纳米晶涂层的耐磨性，5)纳米晶涂层的时间相关特性(应变率敏感性、蠕变和应力松弛)，6)纳米晶涂层的屈服强度。为了实现这些目标，提出了以下方法。首先，采用机械合金化的方法合成Al基合金、Inconel718、Ni和WC/Co纳米晶粉末，重点控制污染、粒度分布和颗粒形态。其次，采用两种不同的方法对机械合金化纳米晶粉末进行固结：热压、热等静压或热挤压以及高速氧气-燃料(HVOF)热喷涂制备纳米晶块体样品或涂层。第三，详细研究了球磨态、固结态和超音速火焰喷涂纳米晶粉末的物理力学性能，重点研究了高速氧燃料喷涂制备的各种纳米晶涂层。此外，还将研究固结纳米晶材料中的Hall-Petch强化机制。该仪器将由加州大学欧文分校的学生和教职员工共享。人们希望这项研究将影响纳米晶体材料的生长，创造出颗粒尺寸小于100纳米的大块3-D样品，这将极大地提高所有表现出这种行为的材料的性能。这将影响材料的强度、耐腐蚀性，并提高机械性能。***

9803045 Lavernia This award provides support for the acquisition of a nanoindenter to serve the research needs of several ongoing, as well as future research programs dealing with the synthesis-structure-property studies of nanocrystalline materials at the University of California at Irvine. Nanocrystalline materials provide the material scientist/engineer with the unique opportunity to achieve combinations of properties that are otherwise unachievable with equilibrium materials. For example, nanophase ceramics are reported to exhibit unusually high ductilities, whereas nanophase metals are noted to exhibit ultra-high hardness values. To that effect, the objective of the research program proposed herein is to investigate the various aspects of mechanical properties of nanocrystalline materials, including powders, coatings and bulk samples produced at the University of California at Irvine. More specifically, the research program will investigate: 1) the evolution of microhardness of various metals, ceramics and cermets as a function of grain size during ball milling, 2) experimental study of the microhardness depth distribution in thermal sprayed nanocrystalline coatings as a function of grain size, porosity and second phase dispersoids (dependent on cooling rate and the coating thickness), 3) Young's modulus behavior (depending on grain size and porosity of various nanocrystalline materials), in particular those present in small dimensions, 4) wear resistance of nanocrystalline coatings with low porosity, 5) time dependent properties (strain rate sensitivity, creep and stress relaxation) of nanocrystalline coatings, and 6) yield strength of nanocrystalline coatings. To accomplish these objectives the following approach is proposed. First, mechanical alloying will be used to synthesize nanocrystalline powders of Al based alloys, Inconel 718, Ni and WC/Co, emphasizing the control of contamination, particle size distribution and particle morphology. Second , the mechanically alloyed nanocrystalline powders will be consolidated using two different approaches: hot pressing, hot isostatic pressing or hot extrusion and high velocity oxygen-fuel (HVOF) thermal spraying to prepare nanocrystalline bulk samples or coatings. Third, the physical and mechanical properties of the as-milled, consolidated and HVOF thermal sprayed nanocrystalline powders will be studied in detail, paying particular attention to various nanocrystalline coatings prepared by high velocity oxygen-fuel spraying. Moreover, Hall-Petch strengthening mechanisms in the consolidated nanocrystalline materials will be studied. %%% This instrument will be shared by students and faculty across the campus at the University of California at Irvine. It is hoped that this research will impact the growth of nanocrytalline materials to create bulk 3-D samples having grain sizes less than 100 nanometers, which would dramatically increase the performance of all materials that display this behavior. This would impact strength of materials, corrosion resistance, and improve mechanical performance. ***