The Influence of Stacking Fault Energy on the Phase Transformations and Deformation Mechanisms in Iron-Manganese Alloys

技术：奥氏体铁锰合金具有优异的机械性能。最近的趋势，在汽车工业对提高安全标准，减轻重量，和成本效益的制造，导致了新的兴趣，这些高强度和？超级坚韧钢. Fe-Mn合金在很大的温度范围（-200至250 ℃）内表现出广泛的韧性和强度，其中低温变形可以显示出75%的伸长率和超过1000 MPa的极限拉伸强度。这些优异的机械性能是由相变诱发塑性（TRIP）效应产生的，这与奥氏体钢中的低本征层错能（SFE）有关。Al、Si、C、N等元素的加入对超临界流体的作用机理和变形机制都有较大的影响。当SFE受到影响时，温度相关塑性可以从TRIP转变为孪生诱导塑性（TTRIP）。尽管在过去的50年里，在这一领域已经进行了大量的工作，但对于决定温度依赖的变形机制是位错滑移、应变诱发马氏体还是机械孪晶的基本因素，仍然存在相当大的理解和分歧。本研究以FeMn（AlSi）和FeMnC为模型合金，以更复杂的高Mn-N不锈钢材料为研究对象，系统地研究了合金元素（Mn、Al、Si、C、N）对这些奥氏体材料超临界流体萃取的影响。研究的一个主要目标是发展奥氏体Fe-Mn合金的SFE作为成分和温度的函数的定量测量与温度相关的机械变形机制之间的结构性能关系。这些基础研究将为优化Fe-Mn合金成分提供基础，以改善新型商业合金的机械性能。非技术性：这项研究涉及范德比尔特大学、马克斯-普朗克研究所和橡树岭国家实验室之间的合作。这种合作不仅有助于为研究提供强有力的科学方法，还将为该计划提供教育部分，研究生和本科生将在国家实验室接触国际互动和最先进的设施。本科生将参与该计划，既有高级独立研究机会，也有暑期实习机会。参与该计划的研究生将接受从事材料科学与工程职业所需的培训。当前项目的第二个目标是将代表性不足的群体培养为未来的科学家。私家侦探该项目的负责人（范德比尔特/菲斯克IGERT计划的共同PI和范德比尔特跨学科材料科学计划的主任）致力于增加范德比尔特博士的多样性。程序.他目前是范德比尔特/菲斯克IGERT少数民族学生之一的首席顾问，这个NSF资助的项目将为未来对范德比尔特博士学位感兴趣的新菲斯克硕士生提供支持。该研究计划有可能为未来科学家的教育，培训和知识做出重大贡献。

TECHNICAL: Austenitic Fe-Mn alloys have exceptional mechanical properties. Recent trends in the automotive industry towards improved safety standards, reduced weight, and cost effective manufacturing have led to a renewed interest in these high strength and ?super tough? steels. Alloys of Fe-Mn exhibit extensive ducility and strength over a large temperature range (-200 to 250 C) where low temperature deformation can show elongation 75% and ultimate tensile strength over 1000 MPa. These outstanding mechanical properties are produced by the transformation induced plasticity (TRIP) effect, which is related to the low intrinsic stacking fault energy (SFE) in austenitic steels. The additions of elements such as Al, Si, C, and N have large influences on both the SFE and deformation mechanism. Temperature dependent plasticity can change from TRIP to twinning induced plasticity (TWIP) when the SFE is affected. Although extensive work has been performed in this area over the last 50 years, there is still a considerable lack of understanding and disagreement for the underlying factors that determine whether the temperature dependent deformation mechanism will be dislocation glide, strain induced martensite, or mechanical twinning. The research is a systematic study with model FeMn(AlSi) and FeMnC alloys as well as more complex high Mn-N stainless steel materials to investigate the influence of alloys elements (Mn, Al, Si, C, N) on the SFE for these austenitic materials. A major objective of the research is the development of structure property relationships between quantitative measurements of SFE as a function of composition and temperature and the temperature dependent mechanical deformation mechanisms for austenitic Fe-Mn alloys. These fundamental studies will provide the basis for optimizing the Fe-Mn alloy composition to achieve improved mechanical properties in new commercial alloys. NON-TECHNICAL: The research involves collaboration between Vanderbilt University, the Max-Planck Institut fur Eisenforschung, and Oak Ridge National Laboratory. This collaboration will not only serve to make a strong scientific approach to the research, it will also provide an educational component to the program where both graduate students and undergraduate students will be exposed to international interactions and state-of-the-art facilities at a national laboratory. Undergraduates will be involved in this program with both senior independent research opportunities and summer internships. Graduate students involved in this program will receive the training required to pursue a career in Materials Science and Engineering. A second objective of the current project is to train underrepresented groups as future scientists. The P.I. of this project (co-PI for the Vanderbilt/Fisk IGERT program and director of the Vanderbilt Interdisciplinary Materials Science Program) is dedicated to increasing the diversity of the Vanderbilt Ph.D. program. He is currently the principal advisor for one of the Vanderbilt/Fisk IGERT minority students, and this NSF funded program would provide for future support of new Fisk masters students interested in a Vanderbilt Ph.D. The research program has the potential to make major contributions to the education, training and knowledge of future scientists.