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Mechanizmy umocnienia oraz degradacji żarowytrzymałej stali austenitycznej

Golański Grzegorz, Wieczorek Paweł, Gredka Anna, Maternicki Marcin, Grodzki Jacek

Energetyka

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2024

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nr 7

278--283

PL

W artykule na przykładzie stali Super 304H scharakteryzowano mechanizmy umocnienia oraz procesy degradacji zachodzące w czasie eksploatacji nowoczesnych, żarowytrzymałych stali austenitycznych.

EN

The paper describes the mechanisms of strengthening and the processes of degradation running during the service of modern creep-resisting austenitic steels on the example of Super 304H steel.

2

Comparative analysis of cold and warm rolling on tensile properties and microstructure of additive manufactured Inconel 718

Zhang Tao, Li Huigui, Gong Hai, Wu Yunxin, Ahmad Abdulrahaman Shuaibu, Chen Xin, Zhang Xiaoyong

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e44, 2022

EN

Despite the high efficiency and low cost of wire + arc additive manufacture (WAAM), the epitaxial grown columnar dendrites of WAAM deposited Inconel 718 cause inferior properties and severe anisotropy compared to the wrought components. Fundamental studies on the influence of one-pass cold and warm rolling on hardness and microstructure were investigated. Then the interpass cold and warm rolling on tensile properties were also analyzed. The results show that the one-pass rolling increases the hardness and displays a heterogeneous hardness distribution compared to the as-deposited material, and the warm rolling exhibits a larger and deeper strain compared to cold rolling. The columnar dendrites gradually change to cell dendrites under the rolling process and then change to equiaxed grains with the subsequent new layer deposition. The average grain size is 16.8 μm and 23.5 μm for the warm and cold rolling, respectively. The strongly textured columnar dendrites with preferred < 001 > orientation transform to equiaxed grains with random orientation after rolling process. The grain refinement contributes to the dispersive distributed strengthening phases and the increase in its fraction with heat treatment. The as-deposited samples show superior tensile properties compared to the cast material but inferior compared to the wrought components, while the warm-rolled samples show superior tensile properties to wrought material. Isotropic tensile properties are obtained in warm rolling compared to cold rolling. The rolling process and heat treatment both decrease the elongation and lead to a transgranular ductile fracture mode. Finally, the rolling-induced strengthening mechanism was discussed.

3

Optimization of Al-Cu Cast Alloy Composition for Hydraulic Valves

Li Rong, Chen Lunjun, Zeng Qi, Su Ming, Xie Zhiping

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 1

84--94

EN

In order to identify the influence of different Mn, Cd, V and Zr content on the properties of Al-Cu casting alloys in hydraulic valves, orthogonal test methods were used to prepare alloy test bars with different elements and contents. Tensile tests were performed on the test bars so obtained. The microstructure of alloys with different compositions is studied. The results show that adding approximately 0.4% of Mn can not only form a strengthening phase but also reduce the excessive segregation of the matrix along the grain boundary. A Cd content of 0.2% can promote the formation of micro Cd spheres in the softer aluminum matrix. Hard spots increase the wear resistance of the material; however, an excess of Cd will cause element segregation and deteriorate the mechanical properties of the valve body. Zr and V refine the grains in the alloy; however, an excess of these elements will lead to a large area of segregation. If proper heat treatment is lacking, the mechanical properties of the valve body deteriorate.

4

Mechanical properties and microstructure of high-manganese TWIP, TRIP and TRIPLEX type steels

Dobrzański L. A., Borek W.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 2

230--238

EN

Purpose: The aim of this paper is to determine the high-manganese austenite propensity to twinning induced by the cold working and its effect on structure and mechanical properties, and especially the strain energy per unit volume of new-developed high-manganese Fe-Mn-(Al, Si) investigated steels, including selected high-manganese austenitic TWIP steels containing 25-27.5% Mn, 1-4% Si, 2-3% Al, high-manganese TRIP steels containing 17-18% Mn, about 1% Si, about 3% Al and selected high-manganese TRIPLEX steels containing 24% Mn and about 11% Al and some of that steels with Nb and Ti microadditions, with various structures after their heat- and thermo-mechanical treatments. Design/methodology/approach: The microstructure evolution in successive stages of deformation was determined in metallographic investigations using light, scanning and electron microscopies as well as X-ray diffractomiter. Findings: New-developed steels achieve profitable connection of mechanical properties, i.e. (ultimate tensile strength) UTS~800-1000 MPa, (yield strength) YS0.2 = 250-450 MPa, and plastic (uniform elongation) UEl = 35-90%, and moreover, particularly strong formability and strain hardening occurring during forming. The new-developed high-manganese Fe-Mn-(Al, Si) steels provide an extensive potential for automotive industries through exhibiting the twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) mechanisms. Practical implications: The obtained microstructure - hot-working conditions relationships and stress-strain curves can be useful in determination of power-force parameters of hot-rolling for sheets with fine-grained austenitic structures. Originality/value: Results obtained for new-developed high-manganese austenitic steels with the properly formed structure and properties in the heat treatment- or thermo-mechanical processes indicate the possibility and purposefulness of their employment for constructional elements of vehicles, especially of the passenger cars to take advantage of the significant growth of their strain energy per unit volume which guarantee reserve of plasticity in the zones of controlled energy absorption during possible collision resulting from activation of twinning for TWIP steels, supported with martensitic transformation for TRIP steels, induced cold working, which may result in significant growth of the passive safety of these vehicles’ passengers.