Metallurgy Division Publications - NISTIR 7248

Division Overview

The Metallurgy Division mission is to provide critical leadership in the development of measurement methods, standards, and fundamental understanding of materials behavior needed by U.S. industry. In extensive collaborations with industry and other agencies, this year we have focused on complex metallurgical issues in microelectronics, magnetics, automotive, and civil infrastructure areas. In this summary, we describe highlights of the past year, as well as demonstrate how the capabilities of the NIST Metallurgy Division are being used to solve problems important to the national economy and the materials metrology infrastructure.

Establishing Priorities

We examine a wide range of possible research topics and make choices for our research portfolio based on well-tested criteria: the match to the NIST and Division missions, the magnitude and immediacy of the need, whether our contribution is critical for success, the anticipated impact relative to our investment, our ability to respond in a timely fashion with high-quality output, and the opportunity to advance mission science, particularly in areas we believe are important for the future.

We establish our research priorities through extensive interaction with U.S. industry and other federal agencies, using a variety of methods, including roadmapping activities, workshops, technical meetings, standards committee participation, and consultation with scientific and technical leaders. A key aspect is translating our fundamental science into a form useful to our partners, integrating measurements, standards, software tools, and evaluated data as needed to solve industry needs.

We prefer to work in rapidly evolving technologies, where advances in measurement science are needed to understand the limitations on system behavior and, therefore, where our contributions are likely to have an impact on the course of technology. For NIST as a whole and the Metallurgy Division in particular, we are committed to having an impact on nanotechnology, homeland security, health care, and the materials infrastructure required for advances in information technology. Over the last two years, we have shifted substantial resources into the areas of nanomagnetics, nanomechanics, nanostructure fabrication, and critical infrastructure protection.

Division Organization

Carol Handwerker led the Division as Chief for the past nine years. Unfortunately for the division, she has now taken an academic position at Purdue University. Frank Gayle has assumed the position of Acting Chief.

This year we reorganized into four technical groups, each consisting of about 10 staff members and a like number of guest researchers.

• The Thin Film and Nanostructure Fabrication Group performs cutting edge research in fabrication techniques that range from electrochemical processing to vapor-liquid-solid growth of nanowires.
• The Thermodynamics and Kinetics Group develops new theory, simulation methods, and data for predicting and controlling phase transformations during materials fabrication processes.
• The Magnetic Materials Group develops new materials and metrology that allow magnetic devices and sensors to be created at smaller size scales and with greater sensitivities.
• The Materials Performance Group develops new theory and measurements for characterizing the mechanical behavior of materials, with applications as varied as sheet metal forming and critical infrastructure protection.

Division Highlights

By virtue of the interdisciplinary nature of materials problems, teams are formed across the Division, MSEL, and NIST, and, in most cases, with external partners in order to meet our project goals. A few highlights of the past year are presented here, grouped by focus areas.

Safety and Reliability

The nation's infrastructure continues to age and is ever more vulnerable to catastrophic failures, whether accidental, intentional, or due to forces of nature. To address infrastructure vulnerability issues, we have started a number of projects, several in close collaboration with the Materials Reliability Division (MRD).

This year, NIST completed the three-year Investigation of the World Trade Center Disaster. A critical aspect of the investigation was the metallurgical analysis of the recovered structural steel performed by the Metallurgy Division with MRD. We issued six reports totaling 1500 pages, and we continue to work on issues impeding the use of fire-resistant steel.

In FY05 we expanded our efforts on pipeline safety in a project working with DoT's Office of Pipeline Safety and DoE, with MRD focusing on crack arrest behavior, and Metallurgy addressing corrosion issues, including topics arising at a Metallurgy-organized Pipeline Coatings Workshop held at NIST.

Advanced Manufacturing Methods

A software tool, FiPy, for simulating phase transformations was released to the public. FiPy gives materials scientists, physicists, and chemists the ability to simulate phase transformations using state-of-the-art, sophisticated numerical techniques for partial differential equations that allow dramatically faster solutions to be found over larger physical domains and for longer elapsed simulation times.

NUMISHEET, a triennial international conference on simulation techniques for sheet metal forming, was held in Detroit in August 2005. Division scientists served on two organizing committees, gave a plenary lecture, and several additional invited talks. An integral part of this conference is a round-robin simulation exercise where modeling groups try to predict the final sample shape from a prototypical forming operation. MSEL played the key role in providing new benchmark data using its unique capabilities for in situ and ex situ stress measurement. Through thickness residual stresses were measured at the NCNR, and surface stresses in a sheet under load in a die were measured using a newly developed X-ray stress measurement system integrated into our metal forming machine.

Nanometrology

A new magnetoresistance (MR) effect discovered this year by scientists in the Metallurgy Division is antisymmetric with respect to magnetic field. This new MR effect is due to the presence of circulating currents created around domain walls when the magnetization vector, current direction, and domain wall are mutually perpendicular. This effect may provide device designers with much more flexibility in designing magnetic switches and memory.

A new strategy for selecting appropriate catalytic metals for vapor-liquid-solid growth of ZnO nanowires with specific semiconducting properties was developed by combining thermodynamic information from phase diagrams with a high-throughput (combinatorial) approach recently demonstrated by the MSEL Metallurgy Division for metallizations to wide-band-gap semiconductors.

Materials for Microelectronics

Spontaneous formation of tin whiskers on thin films of lead-free solder is an enormous reliability issue in the conversion of microelectronics to lead-free solders.

The mechanism responsible for the nucleation and growth of Sn whiskers is a matter of considerable debate. Our research this year has eliminated several of the possible mechanisms and points to critical experiments needed to distinguish among some of the remaining possible mechanisms. Knowing the mechanism for whisker formation will be key to the control and hopefully suppression of Sn whisker formation.

Our past work provided tools to chip manufacturers for on-chip copper interconnect development for next generation chips. We have moved successfully into several new and exciting areas: we have included the impact of leveling additives in our Curvature Enhanced Accelerator Coverage (CEAC) model - these are used industrially to control overfill bump formation; we have demonstrated gold superfill; we have completed a thorough assessment of the issues relevant to successful wetting and superfill of copper on ruthenium barriers that is already being requested by industry and will be key to successful implementation in industry, should it occur; we have achieved seedless superfill on osmium barriers, potentially superior to ruthenium as a diffusion barrier, a key issue for barriers for seedless superfill; we have started new projects on seedless superfill and experimental studies of leveling agents.

Recognition

Bill Egelhoff became a NIST Fellow, the highest scientific and technical position at NIST.

Lyle Levine and Richard Fields (retired) were part of a team of scientists that won the Allen V. Astin Measurement Science Award for outstanding achievement in the advancement of measurement science. This award recognized the development of techniques to measure stressÐstrain relationships of materials under high heating-rate, high strain-rate conditions.

The Metallurgy Division was recognized by Science News "News of the Year" in December 2004 for two breakthrough developments:

• Bob Shull led a team which found that a small amount of iron added to Gd₅Ge₂Si₂ resulted in a significantly improved refrigerant, pointing the way to potential commonplace magnetic refrigeration.
• Jim Warren (Metallurgy) and Jack Douglas (Polymers) were recognized for showing a duality between kinetic and static effects controlling microstructure during solidification.

Frank W. Gayle
Acting Chief, Metallurgy Division