Microstructural characterization of bulk metallic glass welded interfaces by TEM

• Grant number: 18/12960-2
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Effective date (Start): January 07, 2019
• Effective date (End): July 06, 2019
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Marcelo Falcão de Oliveira
• Grantee: Carolina Soares
• Supervisor: Michael Joseph Kaufman
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Research place: Colorado School of Mines, United States
• Associated to the scholarship: 17/10052-9 - Microstructural characterization of welded joints in Zr-based amorphous metallic alloys, BP.MS

Abstract

Metallic glasses are amorphous metallic alloys that are continuously cooled from liquid state at a higher rate than critical. The fast cooling rate does not allow atoms to organize as crystalline structures with long-range order, so they have local and medium range order only. The poor glass-forming ability presented by the first ever developed metallic glasses limited its thickness to micrometers. Through the development of alloys with a higher glass-forming ability, the production of Bulk Metallic Glasses (BMG) became possible, which have a thickness greater than 1 mm. Even though these materials bear superior strength and elastic limit when compared to crystalline alloys, there are limitations to their use. One of them is the lack of weldability, since the thermal input of the welding process can lead to the devitrification of the heated affected zone. Therefore, understanding the relationship between welding parameters and microstructure of welded joints is of fundamental importance to the expansion of BMG applications. This project aims to characterize the microstructure of the interface of resistance upset welded joints of Zr-based BMG VitreloyÒ 105 welded with different thermal inputs and pressure via TEM with EDS. The challenging effort of producing samples by traditional TEM methods makes it necessary to use Focused Ion Beam (FIB) technique to extract samples of the welded interface.