On strengthening of ultrafine grained austenitic steels subjected to large strain deformation

The structural recrystallization mechanisms operating in an Fe – 27%Cr – 9% Ni dual-phase (ferrite-austenite) stainless steel after large strain processing to total strain of 4.4 were investigated in the temperature range of 400-700oC. The severe deformation resulted in the development of an ultrafine grained microstructure consisting of highly elongated grains/subgrains with transverse dimensions of 160 nm and 130 nm in ferrite and austenite, respectively. The annealing mechanism operating in ferrite phase was considered as continuous recrystallization, which involved recovery leading to the development of essentially polygonized microstructure. On the other hand, the mechanism of discontinuous nucleation took place at an early recrystallization stage in austenite phase.

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Quantitative analysis of microstructure refinement in ultrafine-grained strips of Al6063 fabricated using large strain extrusion machining

Machining Science and Technology ◽

10.1080/10910344.2019.1636264 ◽

2019 ◽

Vol 24 (1) ◽

pp. 42-64

Author(s):

Vipin Kumar Sharma ◽

Vinod Kumar ◽

Ravinder Singh Joshi

Keyword(s):

Quantitative Analysis ◽

Large Strain ◽

Microstructure Refinement ◽

Ultrafine Grained

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Preparation of Ultrafine-Grained Continuous Chips by Cryogenic Large Strain Machining

Metals ◽

10.3390/met10030398 ◽

2020 ◽

Vol 10 (3) ◽

pp. 398

Author(s):

Haitao Chen ◽

Baoyu Zhang ◽

Jiayang Zhang ◽

Wenjun Deng

Keyword(s):

Mechanical Properties ◽

Room Temperature ◽

Dynamic Recovery ◽

Large Strain ◽

Chip Morphology ◽

Machining Parameters ◽

Orthogonal Machining ◽

Solute Cluster ◽

Ultrafine Grained ◽

Al 7075

Conventional orthogonal machining is an effective severe plastic deformation (SPD) method to fabricate ultrafine-grained (UFG) materials. However, UFG materials produced by room temperature-free machining (RT-FM) are prone to dynamic recovery, which decreases the mechanical properties of UFG materials. In this study, the cryogenic orthogonal machining technique was implemented to fabricate chips that have an abundant UFG microstructure. Solution-treated Al-7075 bulk has been processed in cryogenic temperature (CT) and room temperature (RT) with various machining parameters, respectively. The microstructure, chip morphology and mechanical properties of CT and RT samples have been investigated. CT samples can reach a microhardness of 167.46 Hv, and the hardness of CT samples is higher than that of the corresponding RT samples among all parameters, with an average difference of 5.62 Hv. Piecemeal chip obtained under RT has cracks on its free surface, and elevated temperature aggravates crack growth, whereas all CT samples possess smoother surfaces and continuous shape. CT suppresses dynamic recovery effectively to form a heavier deformation microstructure, and with a higher dislocation density in CT samples, they further improve the chips’ hardness. Also, CT inhibits the formation of solute cluster and precipitation to enhance the formability of material, so that continuous chips are formed.

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Microstructure Evolution during Warm Deformation of Low Carbon Steel with Dispersed Cementite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.558-559.505 ◽

2007 ◽

Vol 558-559 ◽

pp. 505-510 ◽

Cited By ~ 1

Author(s):

J. Gallego ◽

Alberto Moreira Jorge ◽

O. Balancin

Keyword(s):

Microstructure Evolution ◽

Large Strain ◽

Cell Structure ◽

Lath Martensite ◽

Low Carbon Steel ◽

Testing Temperature ◽

Equivalent Strain ◽

Low Carbon ◽

Ultrafine Grained ◽

Ebsd Technique

The microstructure evolution and mechanical behavior during large strain of a 0.16%CMn steel has been investigated by warm torsion tests. These experiments were carried out at 685 °C at equivalent strain rate of 0.1 s-1. The initial microstructure composed of a martensite matrix with uniformly dispersed fine cementite particles was attained by quenching and tempering. The microstructure evolution during tempering and straining was performed through interrupted tests. As the material was reheated to testing temperature, well-defined cell structure was created and subgrains within lath martensite were observed by TEM; strong recovery took place, decreasing the dislocation density. After 1 hour at the test temperature and without straining, EBSD technique showed the formation of new grains. The flow stress curves measured had a peculiar shape: rapid work hardening to a hump, followed by an extensive flow-softening region. 65% of the boundaries observed in the sample strained to ε = 1.0 were high angle grain boundaries. After straining to ε = 5.0, average ferrite grain size close to 1.5 1m was found, suggesting that dynamic recrystallization took place. Also, two sets of cementite particles were observed: large particles aligned with straining direction and smaller particles more uniformly dispersed. The fragmentation or grain subdivision that occurred during reheating and tempering time was essential for the formation of ultrafine grained microstructure.

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High-strength ultrafine-grained titanium 99.99 manufactured by large strain plastic working

Journal of Materials Science ◽

10.1007/s10853-019-04291-0 ◽

2019 ◽

Vol 55 (11) ◽

pp. 4910-4925 ◽

Cited By ~ 1

Author(s):

Krzysztof Topolski ◽

Bogusława Adamczyk-Cieślak ◽

Halina Garbacz

Keyword(s):

Large Strain ◽

High Strength ◽

Plastic Working ◽

Ultrafine Grained

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Optimum Pass Design of Bar Rolling for Producing Bulk Ultrafine-Grained Steel by Numerical Simulation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.1561 ◽

2010 ◽

Vol 654-656 ◽

pp. 1561-1564 ◽

Cited By ~ 5

Author(s):

Tadanobu Inoue

Keyword(s):

Strain Distribution ◽

Large Strain ◽

Rolling Process ◽

Low Carbon ◽

Shape Variation ◽

Element Analysis ◽

Cross Sectional ◽

Ultrafine Grained ◽

Sectional Shape ◽

Ultrafine Grained Steel

The groove design for creating ultrafine-grained low-carbon steel through a caliber rolling process was studied from the viewpoint of the large strain accumulation and cross-sectional shape variation in a bar. A three-dimensional finite element analysis was employed for this purpose. The caliber rolling process of foval (flat-like-oval)/square type was proposed as a method to efficiently introduce a large strain in material. The relationship among the foval configuration, strain, and cross-sectional shape was examined in the caliber rolling. The influence of the equivalent strain distribution by 1st pass (foval rolling) depends strongly on the strain distribution and a cross-sectional shape by 2nd pass, and the foval configuration to accumulate a large strain efficiently was shown. The optimum pass schedule to fabricate a 13mm square bar of ultrafine-grained steel from a 24 mm square bar by caliber rolling at warm working temperatures was proposed.

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