Deformation mechanisms and load distribution in multi-phase engineering materials
Doktorsavhandling, 2021

While the transition to carbon neutral technologies is still in progress, it is vital to reduce the environmental impact of existing processes. The efficiency of combustion processes for e.g. power generation and aviation can be greatly improved by increasing the operating temperature. This, however, requires development of new and improved materials with increased temperature capability. Similarly, materials which enable e.g. storage of hydrogen or liquid natural gas at cryogenic temperatures can contribute to the above transition. Such high performance engineering materials are usually very complex, with many alloying elements and multiple phases. During deformation the behaviour of the phases, and the grains with different orientations within each phase, is a result of elastic and plastic interactions. Quantifying how the stresses and strains are redistributed within and among the phases is essential for the development of quantitative models capable of accurately predicting the macroscopic mechanical response from the single crystal properties.

This thesis explores the use of in-situ neutron diffraction for investigating load partitioning and deformation mechanisms in two different advanced multi-phase materials, a Ni-based superalloy and a eutectic high entropy alloy, across a wide temperature range (from 20 to 1000 K). For the superalloy, the main findings are: (i) the effect of particle size on the deformation mechanisms and load partitioning was consistent across all temperatures; (ii) plastic deformation of the strengthening phase at high stresses occurred at cryogenic temperatures, which has not been previously reported; and (iii) a strong orientation and phase dependence of the damage evolution during high-temperature deformation was observed. In the eutectic high entropy alloy transitions in the deformation mechanisms of the constituent phases were found to occur with increasing temperature, which lead to a new proposed alloy design strategy for optimising the high temperature properties. Further, the role of the phases is reversed at higher temperatures, i.e. the soft phase at lower temperature becomes the reinforcing phase when the temperature increases. The reported results will have a large impact on the development of accurate multi-scale models for property prediction, as well as development and optimization of complex materials which contribute to a sustainable society.

Eutectic high entropy alloys

Load distribution

Electron microscopy

Deformation mechanisms

In-situ neutron diffraction

Superalloys

PJ-salen, Fysik Origo, Kemigården 1
Opponent: Prof. João Quinta da Fonseca, Department of Materials, The University of Manchester, United Kingdom

Författare

Nitesh Raj Jaladurgam

Chalmers, Fysik, Mikrostrukturfysik

Macro- and micro-mechanical behaviour of a γ′ strengthened Ni-based superalloy at cryogenic temperatures

Materials and Design,; Vol. 209(2021)

Artikel i vetenskaplig tidskrift

Nitesh Raj Jaladurgam, Stefanus Harjo and Magnus Hörnqvist Colliander - Phase and orientation-specific mechanical response during high-temperature deformation of a gamma prime strengthened Ni-based superalloy

Nitesh Raj Jaladurgam, Adrianna Lozinko, Sheng Guo, Stefanus Harjo and Magnus Hörnqvist Colliander - Load redistribution in eutectic high entropy alloy AlCoCrFeNi2.1 during high temperature deformation

Can understanding the behaviour of complex engineering materials increase sustainability?
 
Global warming is raising at an alarming rate, with increasing carbon emissions across the world. Large efforts are made to develop renewable technologies, but while this transition occurs it is critically important to make the existing technologies as sustainable as possible. There is a huge potential for efficiency improvement in e.g. power generation and aviation sectors, which rely heavily on combustion processes. A higher operating temperature translates directly to more efficient combustion, lower fuel consumption and reduced emissions. To enable higher operating temperatures complex multi-phase materials are developed. Incidentally, these materials also possess properties which make them suitable for other critical energy applications involving very low (cryogenic) temperatures, such as storage tanks for hydrogen or liquid natural gas. When such materials are deformed during processing or in service, the load will be inhomogeneously distributed between the phases depending on temperature and loading condition, which might be beneficial or detrimental for the performance. Thus, the internal load redistribution during deformation of multi-phase materials is critical and needs to be understood. This is, however, an extremely challenging task due to difficulty in performing relevant measurements. In this work a state-of-the-art approach, in-situ neutron diffraction, is used to investigate the behaviour of two advanced multi-phase engineering materials across a wide temperature range (–253 to 730 °C). We report several new observations, which increase our understanding of how the structure of the material and the deformation conditions affect the behaviour on both microscopic and macroscopic scale. The outcome will help develop more realistic and reliable modelling tools, as well as new and improved materials which can further reduce the environmental impact from combustion processes.

In-situ studies of microstructural evolution during processing and service of high-temperature materials

Stiftelsen för Strategisk forskning (SSF), 2017-01-01 -- 2020-12-31.

Drivkrafter

Hållbar utveckling

Ämneskategorier

Materialteknik

Teknisk mekanik

Metallurgi och metalliska material

Styrkeområden

Energi

Materialvetenskap

Infrastruktur

Chalmers materialanalyslaboratorium

ISBN

978-91-7905-544-8

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5011

Utgivare

Chalmers tekniska högskola

PJ-salen, Fysik Origo, Kemigården 1

Online

Opponent: Prof. João Quinta da Fonseca, Department of Materials, The University of Manchester, United Kingdom

Mer information

Senast uppdaterat

2021-09-17