다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Friction stir welding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the most significant development in metal joining in a decade. Recently, friction stir processing (FSP) was developed for microstructural modification of metallic materials. In this review article, the current state of understanding and development of the FSW and FSP are addressed. Particular emphasis has been given to: (a) mechanisms responsible for the formation of welds and microstructural refinement, and (b) effects of FSW/FSP parameters on resultant microstructure and final mechanical properties. While the bulk of the information is related to aluminum alloys, important results are now available for other metals and alloys. At this stage, the technology diffusion has significantly outpaced the fundamental understanding of microstructural evolution and microstructure–property relationships.

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Friction Stir Welding and Processing

Recent advances in friction-stir welding : Process, weldment structure and properties

Perspectives on Titanium Science and Technology

https://www.tpbin.com/Uploads/Subjects/643149a0-8194-4c67-bf05-73fae6f0d14f.pdf

Development of new metallic alloys for biomedical applications

A detailed investigation of the early stages of secondary austenite precipitation in five duplex stainless steel (DSS) commercial alloys (UNS S32304, S32205, S32550, S32750, and S32760) has been conducted using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Based on this study, a model is proposed that describes the interaction betwee Cr2N and austenite (intergranular and intragranular) precipitation in these alloys. Depending on nitrogen availability and interface mobility, Cr2N precipitation along existing ferrire/austenite interfaces precedes intergranular secondary austenite growth. The low-energy interfaces formed between the Cr2N, the ferrite, and the austenite, along with the coupled diffusion processes, are the factors controlling this phase transformation. Finally, in the case of the intragranular nitrides, a mechanism is proposed whereby the nitrides serve as sites for heterogeneous nucleation of intragranular secondary austenite.

The relationship between chromium nitride and secondary austenite precipitation in duplex stainless steels

The ductility dip cracking susceptibility of two Ni-base filler metals, Filler Metal 52 (59%Ni–29%Cr–9%Fe–1%Mn–1%Al) and Filler Metal 82 (72%Ni–20%Cr–1%Fe–3%Mn–3%Nb) was evaluated using the strain-to-fracture test The analysis of these results and detailed weld metal microstructural characterization (SEM and TEM) was presented in Part I Part II of this work provides new insight into the creep-like, grain boundary sliding mechanism that leads to elevated temperature intergranular cracking in these weld deposits The effect of precipitation on grain boundary tortuosity and sliding, and its influence on ductility-dip cracking resistance is discussed in the context of current theories of high temperature creep Finally, the effect of composition, including both precipitate forming elements and impurity elements, on ductility-dip cracking is discussed

High temperature behavior of Ni-base weld metal: Part II – Insight into the mechanism for ductility dip cracking

Ni-based alloys are a special class of engineering material with excellent corrosion resistance in harsh environments. However, microstructural changes due to the solidification, may result in solidification cracks and reduction in the corrosion resistance. Knowing the microchemical and microstructural evolutions during the solidification of these alloys is essential for the understanding of the relationship between the metallurgical aspects and the properties. This research presents a new insight on the solidification path of alloy 625 weld metals deposited by the TIG cold wire process on the C–Mn steel plates. After the welding, samples having been extracted and evaluated by the scanning electron microscope, transmission electron microscopy and energy dispersive X-ray spectroscopy techniques. The results showed the presence of two types of secondary phases, identified as Laves phase and complex nitride/carbide particles. Due to the presence of nitrides particles, stable in the solid state during the melting of the alloy, during the solidification it is noted the occurrence of a complex nitride/carbide precipitation. This implies in a new route to explain the solidification of the aforementioned alloy.

New insight on the solidification path of an alloy 625 weld overlay

The ductility dip cracking resistance of two Ni-base Filler metals, Filler Metal 52 (FM-52) (59%Ni–29%Cr–9%Fe–1%Mn–1%Al) and Filler Metal 82 (FM-82) (72%Ni–20%Cr–1%Fe–3%Mn–3%Nb) was evaluated using the strain-to-fracture (STF) test. The reinterpretation of previously reported STF test results for these filler metals, is discussed, based on detailed microstructural characterization performed using electron microscopy. In Part II of this paper, new insight into the creep-like, grain boundary (GB) sliding mechanism responsible for intergranular cracking in these filler metals is presented.

Antonio J. Ramirez

Papers

The relationship between chromium nitride and secondary austenite precipitation in duplex stainless steels

High temperature behavior of Ni-base weld metal: Part II – Insight into the mechanism for ductility dip cracking

New insight on the solidification path of an alloy 625 weld overlay

High temperature behavior of Ni-base weld metal: Part I. Ductility and microstructural characterization

Microstructural Evolution in Ti-6Al-4V Friction Stir Welds