# Evaluation of Powder Metallurgy Workpiece Prepared by Equal Channel Angular Rolling

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

**C**is the calibration constant,${\mathit{\sigma}}_{\mathbf{1}}$ is the maximum tensile principal stress, $\overline{\mathit{\sigma}}$ is the effective stress according to the von Mises, is the effective stress, $\overline{{\mathit{\epsilon}}_{\mathit{e}\mathit{f}}}$ is the effective strain at the fracture, and $\overline{\epsilon}$ is the increment of effective strain.

## 2. Materials and Methods

#### 2.1. Materials

#### 2.2. The ECAR Processing

#### 2.3. Formability of Alumix 321

#### 2.4. Initial Conditions for Numerical Simulations of the ECAR Process

^{TM}(version v13.0.1 ). The one ECAR pass was simulated through vertical and horizontal channels which form an angle of 90° to each other. The principle of ECAR processing with individual parts is shown in Figure 1b. The initial dimension of the billet was 7 mm in thickness, 7 mm in width, and 250 mm in length.

## 3. Results

#### 3.1. The ECAR Processing

#### 3.2. Formability of Alumix 321

#### 3.3. FEM Simulation of the ECAR Process

**SPD (zone C)**: it can be characterized as a main shearing deformation zone (MSDZ). It can be identified from the effective strain rate (Figure 5c), which from the side of the inner radius reaches a maximum value of ($\dot{{\phi}_{C}}=1.2{\mathrm{s}}^{-1}$).

## 4. Discussion

#### 4.1. Distribution and Evolution of Stress Triaxiality

#### 4.2. The Stress Triaxiality of the DC Test

#### 4.3. The Stress Triaxiality of the ECAR Process

## 5. Conclusions

- -
- the DIC and FEM were used to study the stress state of the ECAR process and the DC test;
- -
- the relationship between the stress state parameters and failure mode was evaluated using the stress triaxiality versus Lode parameter diagram;
- -
- the damage factor was determined from the DC test, which reaches a value of 0.12 in the place of the crack;
- -
- from FEM simulations is possible to divide the deformation process of the ECAR processing into three deformation areas: shape rolling zone, upsetting zones, and SPD zone, which take place under the plane strain conditions;
- -
- due to the high-pressure hydrostatic stresses in the deformation zones, the material was probably compacted close to 100%;
- -
- the damage factor in the output channel of the ECAR process reaches a value of up to 0.5, which is several times higher than the value measured using the DC test;
- -
- materials with reduced formability, such as sintered PM material, cannot be additionally ennobled by plastic deformations in the ECAR process because in the main deformation zone of the process stress conditions for the pure shear are created, which will cause material violations by shearing fracture;
- -
- when evaluating the formability of the PM material by the DC test, it was found that the DC test can be used for the calibration and verification of various fracture criteria for the stress state located between the pure shear and the axial symmetry compression.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 4.**The diametrical compression test: (

**a**) sample before the DC test with the pattern; (

**b**) sample after the DC test with the pattern and distribution of principal strain (${\phi}_{1}$) using DIC analyses; (

**c**) force comparison between FEM simulation and laboratory DC test; (

**d**–

**f**) distribution of the principal strain (${\phi}_{1FEM}$ ), the damage factor and max. shear stress (${\tau}_{max}$ ) from FEM simulation (displayed in the plane xy), respectively.

**Figure 5.**The distributions of: (

**a**) the flow net; (

**b**) effective strain; (

**c**) strain rate effective; (

**d**) stress effective in the ECAR process. The A, B, and C represent deformation zones: A—Shape Rolling, B—Upsetting, and C—SPD.

**Figure 6.**The force load in the Z-axis direction on the guide, grove roll, top, and bottom die during the ECAR processing. The A, B, and C represent deformation zones: A—Shape Rolling, B—Upsetting, and C—SPD.

**Figure 7.**The distribution of: (

**a**) effective strain; (

**b**) density, and (

**c**) damage factor in cross section of the billet in three zones during the ECAR process. The A, B, and C represent deformation zones: A—Shape Rolling, B—Upsetting, and C—SPD.

**Figure 8.**The stress state analysis of the ECAR process in: (

**a**) Shape Rolling zone (points 1, 2); (

**b**) part of the Upsetting zone (point 3), and SPD zone (points 4–9).

**Figure 9.**The stress state diagram shows the relationship between failure mode and stress state for the conditions of the ECAR process and the DC test.

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## Share and Cite

**MDPI and ACS Style**

Kočiško, R.; Kvačkaj, T.; Bidulská, J.; Bidulský, R.; Petroušek, P.; Pokorný, I.; Lupták, M.; Actis Grande, M.
Evaluation of Powder Metallurgy Workpiece Prepared by Equal Channel Angular Rolling. *Materials* **2023**, *16*, 601.
https://doi.org/10.3390/ma16020601

**AMA Style**

Kočiško R, Kvačkaj T, Bidulská J, Bidulský R, Petroušek P, Pokorný I, Lupták M, Actis Grande M.
Evaluation of Powder Metallurgy Workpiece Prepared by Equal Channel Angular Rolling. *Materials*. 2023; 16(2):601.
https://doi.org/10.3390/ma16020601

**Chicago/Turabian Style**

Kočiško, Róbert, Tibor Kvačkaj, Jana Bidulská, Róbert Bidulský, Patrik Petroušek, Imrich Pokorný, Miloslav Lupták, and Marco Actis Grande.
2023. "Evaluation of Powder Metallurgy Workpiece Prepared by Equal Channel Angular Rolling" *Materials* 16, no. 2: 601.
https://doi.org/10.3390/ma16020601