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

Properties and Application of Geopolymers Vol. 841 (/MSF.841 /book) Development and Investigation of Materials Using Modern Techniques Vol. 840 (/MSF.840/book) Superplasticity in Advanced Materials ICSAM 2015 Vols. 838-839 (/MSF.838-839/book) 12th International Conference on High Speed Machining Vols. 836-837 (/MSF.836-837/book) Sintering Fundamentals II Vol. 835 (/MSF.835/book) Advanced Machining Technologies: Traditions and Innovations Vol. 834 (/MSF.834/book) Applied Materials and Technologies Vol. 833 (/MSF.833/book) Emerging Functional Materials: Book (/MSF.841/book) Papers (/MSF.841)

Materials Science Forum

Quenching and partitioning is a relatively new heat treatment concept to generate microstructures containing retained austenite stabilised by carbon partitioning from martensite. Research on quench and partitioning has been conducted by numerous groups, and this critical assessment provides some of the authors’ perspectives on progress and understanding in the field, with particular focus on the physical metallurgy and transformation mechanisms, process variations, mechanical behaviour, and industrial implementation. While much progress has been made, the field provides rich opportunity for further understanding and development.

https://www.tandfonline.com/doi/pdf/10.1179/1743284714Y.0000000628

Critical Assessment 7: Quenching and partitioning

Outstanding combination of strength and ductility in nanostructured bainitic steels makes them prone to be used as an important engineering material. However, there is still a necessity to investigate their toughness and effective parameters. This work aims to study the fracture toughness of these group of high strength carbide free bainitic steels with respect to chemical composition, transformation temperature, volume fraction and morphology of the present phases in the microstructure. Results indicate that the volume fraction and morphology of high carbon retained austenite together, are important factors affecting the ductility. In addition, higher amount of the lathlike austenite is essential in order to improve fracture toughness. Moreover, it has been shown that controlling the mechanical stability of retained austenite and the primary austenite grain size by Ni and V addition can further influence fracture toughness of nanostructured bainitic steels.

Toughness variations in nanostructured bainitic steels

Semi-solid processing of alloys and composites

http://fortech.zcu.cz/publications/2014/Dr.Jirkov_ISMANAM-2013.pdf

Influence of metastable retained austenite on macro and micromechanical properties of steel processed by the Q&P process

The use of the combined influence of retained austenite and bainitic ferrite to improve strength and ductility has been known for many years from the treatment of multiphase steels. Recently, the very fine films of retained austenite along the martensitic laths have also become the centre of attention. This treatment is called the Q-P process (quenching and partitioning). In this experimental program the quenching temperature and the isothermal holding temperature for diffusion carbon distribution for three advanced high strength steels with carbon content of 0.43 % was examined. The alloying strategies have a different content of manganese and silicon, which leads to various martensite start and finish temperatures. The model treatment was carried out using a thermomechanical simulator. Tested regimes resulted in a tensile strength of over 2000MPa with a ductility of above 14 %. The increase of the partitioning temperature influenced the intensity of martensite tempering and caused the decrease of tensile strength by 400MPa down to 1600MPa and at the same time more than 10 % growth of ductility occurred, increasing it to more than 20%.

/pdf/effect-of-quenching-and-partitioning-temperatures-in-the-q-p-4xp1b30ay2.pdf

Effect of Quenching and Partitioning Temperatures in the Q-P Process on the Properties of AHSS with Various Amounts of Manganese and Silicon

The concepts new types of materials are, for economic reasons, focused mainly on low alloyed steels with a good combination of strength and ductility. Suitable heat and thermo-mechanical treatments play an important role for the utilization of these materials. Different alloying strategies are used to influence phase transformations. The quenching and partitioning process (Q-P Process) is one of the heat treatment methods which can result in a high ultimate strength as well as a good ductility. However, these good properties can be obtained only if a sufficient amount of retained austenite is stabilized. The influence of different contents of manganese, silicon and chromium on microstructural development and mechanical properties were experimentally tested. Alloying elements were used to stabilize the retained austenite in the final microstructure and also to strengthen the solid solution. Ultimate strengths of over 2000MPa with ductility over 10% were reached after the optimization of the Q-P Process. The microstructures were analyzed using several microscopic methods; mechanical properties were determined by a tensile test and the volume fraction of the retained austenite was established by X-ray diffraction phase analysis.

/pdf/the-effect-of-mn-and-si-on-the-properties-of-advanced-high-4e5mt35dgy.pdf

The Effect of Mn and Si on the Properties of Advanced High Strength Steels Processed by Quenching and Partitioning

Existing oxide dispersion strengthened (ODS) alloys are, besides Ni-based superalloy single crystals, the most creep-resistant materials. The creep resistance of the ODS alloys may, moreover, be significantly improved thanks to increasing the volume fraction of the nano oxides by more than one order of magnitude so that the oxides play a decisive role in strengthening. The present experimental study deals with two systems of such a high-volume fraction of nano oxides, namely, the Fe-11Al-1O and Fe-17Cr-7Al-4Y2O3 systems prepared by mechanical alloying and hot rolling leading to a rather stable fine-grained microstructure. This microstructure undergoes static recrystallization at high temperatures. The kinetics of static recrystallization and coarsening of nano oxides in recrystallized grains is determined for both systems. The difference in kinetics of coarsening of Al-based and Y-based oxides in the Fe-11Al-1O and Fe-17Cr-7Al-4Y2O3 systems is expressive and predetermines the Fe-17Cr-7Al-4Y2O3 system or similar ones to become the new leading system among creep- and oxidation-resistant materials for applications up to 1200 °C.

https://dspace5.zcu.cz/bitstream/11025/31159/1/Microstructure%20Evolution%20in%20ODS%20Alloys%20with%20a%20High-Volume%20Fraction%20of%20Nano%20Oxides.pdf

Microstructure Evolution in ODS Alloys with a High-Volume Fraction of Nano Oxides

A nearly abrupt coarsening of grains is observed in a newly developed Fe–Al–O ultra-fine-grained nanocomposite with a significant volume fraction (4%) of alumina nano-precipitates. The micr...

Bohuslav Mašek

Papers

Influence of metastable retained austenite on macro and micromechanical properties of steel processed by the Q&P process

Effect of Quenching and Partitioning Temperatures in the Q-P Process on the Properties of AHSS with Various Amounts of Manganese and Silicon

The Effect of Mn and Si on the Properties of Advanced High Strength Steels Processed by Quenching and Partitioning

Microstructure Evolution in ODS Alloys with a High-Volume Fraction of Nano Oxides

Kinetic study of static recrystallization in an Fe–Al–O ultra-fine-grained nanocomposite