Identification of crystalline phases in samples with high GFA by advanced analysis in electron microscopy

• Grant number: 11/20690-6
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: August 01, 2012
• End date: November 30, 2012
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Transformation Metallurgy
• Principal Investigator: Marcelo Falcão de Oliveira
• Grantee: Nelson Delfino de Campos Neto
• Supervisor: Michael J. Kaufman
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Institution abroad: Colorado School of Mines, United States
• Associated to the scholarship: 10/05250-7 - Casting of small amorphous metallic parts by arc melting and chill quenching, BP.IC

Abstract

This research project develops a study on the production of BMG's by electric arc melting under inert atmosphere of argon and squeeze casting in water cooled copper molds. All cast samples were analyzed by X-ray diffraction (XRD). Some were later analyzed by optical microscopy (OM), SEM/EDS and DSC. Studied samples of ternary Zr-Ni-Cu alloys were wedge-shaped. The Zr-Ni-Cu system has no major studies on GFA and the phase diagram is not well known. The compositions were chosen by the selection criteria of compositions that have high GFA, developed by the supervisor (Marcelo Falcão de Oliveira). Seven alloys were selected with compositions ranging from high to low GFA. These compositions were analyzed by XRD and SEM/EDS. Only small fractions of amorphous phases were detected by XRD and possibly proven by OM. Many crystalline phases, present in the XRD, could not be identified according to the JCPDS database. The Cu46Zr42Al7Y5 alloy, wedge-shaped and 1 mm thick plate, was also produced and analyzed by XRD and OM. For the wedge-shaped sample, it could be seen a completely amorphous structure up to 5 mm in thickness. For the 1 mm thick plate it was observed the contamination effect of air (some crystallization triggered by oxygen). A sample was produced in proper cleaning conditions and showed a completely amorphous structure. On the other hand a sample exposed to the atmosphere, in liquid state, presented some fraction of crystalline phases after solidification, probably containing oxygen, however such phases could not be identified. Samples of Ti-based alloys, rod-shaped plate with 2x2 mm and 1 mm thick, were produced with the interest in their mechanical properties. These samples showed, according to the XRD, crystalline peaks and the presence of small amount of amorphous phase. Fully amorphous samples could not be obtained, most likely because titanium has a great chemical affinity with oxygen favoring the nucleation of undesired crystalline phases, as in the case of Zr-based alloys. One of the major problems in the present project is the correct identification of unknown crystalline phases, not only to serve as a parameter for a better control of raw materials and oxygen in the synthesis process, but also to refine the theoretical calculations to predict the GFA of the metallic systems of interest. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

NELSON DELFINO DE CAMPOS NETO; LEONARDO PRATAVIEIRA DEO; MARCIO ANDREATO BATISTA MENDES; MICHAEL JOSEPH KAUFMAN; MARCELO FALCÃO DE OLIVEIRA. Oxide Formation in a Melt Spun Alloy in the Zr-Ni-Cu System. MATERIALS RESEARCH-IBERO-AMERICAN JOURNAL OF MATERIALS, v. 25, 2022-06-17. (11/20690-6)