Design, Development, and Examination of New Lightweight High-Entropy Alloy for Structural Applications
| dc.contributor.advisor | Tiamiyu, Ahmed A. | |
| dc.contributor.author | Alam, Intekhab | |
| dc.contributor.committeemember | Tiamiyu, Ahmed A. | |
| dc.contributor.committeemember | Egberts, Philip | |
| dc.contributor.committeemember | Shi, Yujun | |
| dc.date | 2024-05 | |
| dc.date.accessioned | 2024-01-05T22:49:39Z | |
| dc.date.available | 2024-01-05T22:49:39Z | |
| dc.date.issued | 2024-01-04 | |
| dc.description.abstract | The use of lightweight materials for structural applications can reduce energy consumption and greenhouse gas emissions towards climate change mitigation. However, lightweight materials must be carefully designed without compromising strength and safety; hence the continued search for high specific-strength materials. This thesis contributes to these efforts: to discover, develop, and characterize lightweight high-entropy alloys (LHEAs) for structural applications. Obtaining solid-solution (SS) in alloys instead of intermetallic (IM) compounds is usually desirable because IM compounds can detrimentally reduce ductility and corrosion resistance. HEAs are multi-principal element alloys in which complex pair-wise interactions between constituent elements can favour IM compound formation. As such, empirical rules for predicting SS formation (over IM compound) and crystal structure in HEAs exist—atomic size difference, enthalpy of mixing, mixing entropy, entropy to enthalpy ratio, Pauling electronegativity difference, and valence electron concentration. However, these rules break down. This thesis first re-examines the empirical rules’ effectiveness by conducting a systematic study that isolates the effect of processing pathways known to impact phase stability. A new conservative phase and SS formation criteria for AlTiCuZn-based LHEAs are proposed; the revised rules are verified by developing new LHEAs that are accurately predicted—AlTi0.37CuZn0.97 and AlTi0.56Cu1.24Zn1.2. As a next step, the thermal degradation pattern of a new dual-phase AlTi0.45CuZn LHEA (ρ=5.71 g/cc) from phase decomposition to evaporation was further investigated. Using multimodal advanced characterization techniques, AlTi0.45CuZn is found to be thermally-stable up to between 250 and 360 °C. Beyond this limit, multistep decomposition occurs: phase decomposition at ~360 °C forms Al-Ti phase off the AlTi0.45CuZn matrix due to the largest negative mixing enthalpy for Al-Ti than other binary pairs; Zn evaporation at ~750 °C due to its faster evaporation rate than other constituent elements; and LHEA melting at 880 °C. The LHEA possesses sluggish grain growth and better nano-indentation hardness among other LHEAs of close density range due to combined grain size and phase strengthening effects. This work offers new insight into the processing-structure-properties relationship of LHEAs and further advances the field’s understanding of LHEA thermal deteriorative behavior in structural applications at elevated temperatures. | |
| dc.identifier.citation | Alam, I. (2024). Design, development, and examination of new lightweight high-entropy alloy for structural applications (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. | |
| dc.identifier.uri | https://hdl.handle.net/1880/117878 | |
| dc.identifier.uri | https://doi.org/10.11575/PRISM/42721 | |
| dc.language.iso | en | |
| dc.publisher.faculty | Graduate Studies | |
| dc.publisher.institution | University of Calgary | |
| dc.rights | University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. | |
| dc.subject | Lightweight high-entropy alloy | |
| dc.subject | Phase stability rules | |
| dc.subject | AlTiCuZn-based LHEA | |
| dc.subject | Thermal degradation | |
| dc.subject | Mechanical property | |
| dc.subject.classification | Metallurgy | |
| dc.subject.classification | Materials Science | |
| dc.title | Design, Development, and Examination of New Lightweight High-Entropy Alloy for Structural Applications | |
| dc.type | master thesis | |
| thesis.degree.discipline | Engineering – Mechanical & Manufacturing | |
| thesis.degree.grantor | University of Calgary | |
| thesis.degree.name | Master of Science (MSc) | |
| ucalgary.thesis.accesssetbystudent | I do not require a thesis withhold – my thesis will have open access and can be viewed and downloaded publicly as soon as possible. |