G. Bharat Reddy , Rajeev Kapoor , Ayan Bhowmik , Apu Sarkar , Bhupendra K. Kumawat , Sanjay Raj
{"title":"Overcoming the strength-ductility trade-off in zirconium using twin boundary engineering","authors":"G. Bharat Reddy , Rajeev Kapoor , Ayan Bhowmik , Apu Sarkar , Bhupendra K. Kumawat , Sanjay Raj","doi":"10.1016/j.msea.2024.147602","DOIUrl":null,"url":null,"abstract":"<div><div>Tailoring the strength and ductility of metals through microstructural design has been a longstanding endeavour. Here, we report the development of a hierarchical ultrafine twinned microstructure in zirconium <em>via</em> a novel multi-axial cryo-forging (MACF) process. MACF of Zr resulted in the formation of dense and fine tensile twins, <span><math><mo>{</mo><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo><mo><</mo><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn></mrow><mo>></mo></math></span> (T-1) and <span><math><mrow><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>‾</mo></mover><mn>1</mn></mrow><mo>}</mo></mrow><mrow><mo>⟨</mo><mrow><mover><mn>1</mn><mo>‾</mo></mover><mover><mn>1</mn><mo>‾</mo></mover><mn>26</mn></mrow><mo>⟩</mo></mrow></mrow></math></span> (T-2) within coarse and equiaxed grains. This microstructure exhibited a remarkable combination of enhanced strength, strain-hardening rate, and ductility, compared to its coarse-grained counterpart. The yield strength and ultimate tensile strength increased by up to 26 % and 30 %, respectively, without compromising material ductility. The improved strength and strain-hardening stemmed from the activation of the harder <c+a> slip system and its consequent interaction with the fine twin boundaries. Notably, the growth of fine T-2 twins during ambient temperature deformation, absent in coarse-grained zirconium, contributed to additional ductility. Crystal plasticity simulations reveal that the activity of pyramidal <c+a> slip within T-2 twins is twice that of prismatic <a> slip, leading to an enhanced strain-hardening rate contributed by the T-2 twins. Subsequent heat treatment of MACF Zr at 500 °C relieved the elastic distortions around twin boundaries, and hence tensile straining led to stress-assisted easier migration of pre-existing twin boundaries. This resulted in a lowering of the strain-hardening rates. It was shown that the dislocation substructure around these typically incoherent tensile twins in hcp metals plays a crucial role in their strain-hardening behaviour.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"921 ","pages":"Article 147602"},"PeriodicalIF":6.1000,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Materials Science and Engineering: A","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0921509324015338","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Tailoring the strength and ductility of metals through microstructural design has been a longstanding endeavour. Here, we report the development of a hierarchical ultrafine twinned microstructure in zirconium via a novel multi-axial cryo-forging (MACF) process. MACF of Zr resulted in the formation of dense and fine tensile twins, (T-1) and (T-2) within coarse and equiaxed grains. This microstructure exhibited a remarkable combination of enhanced strength, strain-hardening rate, and ductility, compared to its coarse-grained counterpart. The yield strength and ultimate tensile strength increased by up to 26 % and 30 %, respectively, without compromising material ductility. The improved strength and strain-hardening stemmed from the activation of the harder <c+a> slip system and its consequent interaction with the fine twin boundaries. Notably, the growth of fine T-2 twins during ambient temperature deformation, absent in coarse-grained zirconium, contributed to additional ductility. Crystal plasticity simulations reveal that the activity of pyramidal <c+a> slip within T-2 twins is twice that of prismatic <a> slip, leading to an enhanced strain-hardening rate contributed by the T-2 twins. Subsequent heat treatment of MACF Zr at 500 °C relieved the elastic distortions around twin boundaries, and hence tensile straining led to stress-assisted easier migration of pre-existing twin boundaries. This resulted in a lowering of the strain-hardening rates. It was shown that the dislocation substructure around these typically incoherent tensile twins in hcp metals plays a crucial role in their strain-hardening behaviour.
期刊介绍:
Materials Science and Engineering A provides an international medium for the publication of theoretical and experimental studies related to the load-bearing capacity of materials as influenced by their basic properties, processing history, microstructure and operating environment. Appropriate submissions to Materials Science and Engineering A should include scientific and/or engineering factors which affect the microstructure - strength relationships of materials and report the changes to mechanical behavior.