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15 pages, 7071 KiB

Open AccessArticle

Influence of Strain Route Changes on the Microstructure and Mechanical Properties of CuZn36 Alloy during Cross Channel Extrusion CCE

by Radosław Łyszkowski

Materials 2022, 15(3), 1124; https://doi.org/10.3390/ma15031124 - 31 Jan 2022

Cited by 4 | Viewed by 2367

Abstract

This study evaluates the impact of changing the deformation routes of the extrusion process in a cross-shaped die (CCE) on the structure and properties of a CuZn36 alloy (% at.). Samples with dimensions of Ø8 × 36 mm were subjected to extrusion at room temperature according to two variants: straight extrusion in the A route (2-, 4-, 8- and 12-pass) and extrusion with interoperative rotation by 90° in the B_C route (2- and 4-pass). The improvement of strength properties was obtained as a result of grain fragmentation in the CCE process. Changes in the microstructure were observed using a light microscope, and mechanical properties were measured in the microhardness test and a static tensile test. The obtained results showed that the mechanical properties of the alloy depend on the number of passes and the material deformation route. This observation was related to the fragmentation of its structure and strengthening, which resulted in changes in its properties. The highest strength was characterized by the material pressed four times with the rotation of 90° (B_C route), whose properties were comparable and even slightly better than the material squeezed twelve times without rotation (A route). Full article

(This article belongs to the Special Issue Progress in Plastic Deformation of Metals and Alloys)

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21 pages, 8682 KiB

Open AccessArticle

The Influence of A Cross-Channel Extrusion Process on The Microstructure and Properties of Copper

by Radosław Łyszkowski, Magdalena Łazińska and Dariusz Zasada

Materials 2019, 12(23), 3995; https://doi.org/10.3390/ma12233995 - 2 Dec 2019

Cited by 3 | Viewed by 3416

Abstract

A new cross-channel extrusion (CCE) method with the application of a back pressure (BP) is proposed and experimentally tested. The introduction of pressure blocks the free flow of material by using an additional set of pistons, which prevents the loss of consistency. The paper presents results of experimental trials of CCE process. Between one and eight passes of CCE with and without a BP were applied to pure copper billets to refine their initial coarse-grained microstructure at room temperature. It was found that processing by CCE results in the formation of a lamellar structure along the extruded axis and the fine-grained structure in the remaining volume. The material exhibited dynamic recrystallization, which results in the formation of 0.5- to 2-μm grains after one pass and 2- to 8-μm grains after four CCE passes. The fine-grained material had YS of 390-415 MPa. An increase in the microhardness from 70 to 130 HV02 after one pass and then a decrease after four passes were observed. This might indicate that secondary recrystallization and selective grain growth occur, because an exothermic peak (158.5 °C, 53 ± 2.1 J/mol) was observed during DSC (differential scanning calorimetry) testing. The resistivity of the once deformed copper significantly decreases, while its further processing causes the resistivity to increase. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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17 pages, 6760 KiB

Open AccessArticle

Severe Plastic Deformation of Fe-22Al-5Cr Alloy by Cross-Channel Extrusion with Back Pressure

by Radosław Łyszkowski, Wojciech Polkowski and Tomasz Czujko

Materials 2018, 11(11), 2214; https://doi.org/10.3390/ma11112214 - 8 Nov 2018

Cited by 9 | Viewed by 3202

Abstract

A new concept of the cross-channel extrusion (CCE) process under back pressure (BP) was proposed and tested experimentally. The obtained by finite element method (FEM) results showed that a triaxial compression occurred in the central zone, whereas the material was deformed by shearing in the outer zone. This led to the presence of a relatively uniformly deformed outer zone at 1 per pass and a strong deformation of the paraxial zone (3–5/pass). An increase in the BP did not substantially affect the accumulated strain but made it more uniform. The FEM results were verified using the physical modeling technique (PMT) by the extrusion of clay billet. The formation of the plane of the strongly flattened, and elongated grains were observed in the extrusion directions. With the increase in the number of passes, the shape of the resulting patterns expanded, indicating an increase in the deformation homogeneity. Finally, these investigations were verified experimentally for Fe-22Al-5Cr (at. %) alloy using of the purposely designed tooling. The effect of the CCE process is the fragmentation of the original material structure by dividing the primary grains. The complexity of the stress state leads to the rapid growth of microshear bands (MSB), grain defragmentation and the nucleation of new dynamically recrystallized grains about 200–400 nm size. Full article

(This article belongs to the Special Issue Structure and Mechanical Properties of Transition Group Metals, Alloys, and Intermetallic Compounds)

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