{"id":30161,"date":"2021-06-21T06:54:03","date_gmt":"2021-06-21T06:54:03","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=30161"},"modified":"2023-09-14T09:05:12","modified_gmt":"2023-09-14T09:05:12","slug":"grain-refinement-grain-boundary-strenthening","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/metals-what-are-metals\/metalworking\/grain-refinement-grain-boundary-strenthening\/","title":{"rendered":"Grain Refinement &#8211; Grain Boundary Strenthening"},"content":{"rendered":"<div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\">\n<h2>Strengthening of Metals<\/h2>\n<p>The strength of metals and alloys can be modified through various combinations of cold working, alloying, and heat treating. As discussed in the previous section, the ability of a crystalline material to deform largely plastically depends on the ability for dislocation to move within a material. Therefore, impeding the movement of dislocations will result in the strengthening of the material. For example, a microstructure with finer <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/materials-science\/crystal-structures\/grain-structure-grains-in-crystalline-materials\/\">grains<\/a> typically results in higher strength and superior toughness than the same alloy with physically larger grains. In the case of grain size, there may also be a tradeoff between strength and creep characteristics. Other strengthening mechanisms are achieved at the expense of lower ductility and toughness. There are many strengthening mechanisms, which include:<\/p>\n<ul>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/metals-what-are-metals\/metalworking\/solid-solution-strengthening-alloying\/\"><strong>Solid Solution Strengthening<\/strong> (alloying)<\/a><\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/metals-what-are-metals\/metalworking\/work-hardening-cold-working\/\"><strong>Work Hardening (Cold Working)<\/strong><\/a><\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/metals-what-are-metals\/metalworking\/precipitation-hardening-age-hardening\/\"><strong>Precipitation Hardening<\/strong><\/a><\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/metals-what-are-metals\/metalworking\/grain-refinement-grain-boundary-strenthening\/\"><strong>Grain Refinement<\/strong><\/a><\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/metals-what-are-metals\/metalworking\/transformation-hardening-martensitic-transformation-hardening\/\"><strong>Transformation Hardening<\/strong><\/a><\/li>\n<\/ul>\n<h2>Grain Refinement \u2013 Grain Boundary Strengthening<\/h2>\n<figure id=\"attachment_27618\" aria-describedby=\"caption-attachment-27618\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/10\/Grains-Grain-Boundaries.png\"><img loading=\"lazy\" class=\"wp-image-27618 size-medium\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/10\/Grains-Grain-Boundaries-300x160.png\" alt=\"Grains - Grain Boundaries\" width=\"300\" height=\"160\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/10\/Grains-Grain-Boundaries-300x160.png 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/10\/Grains-Grain-Boundaries.png 621w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-27618\" class=\"wp-caption-text\">Grains and Boundaries Source: U.S. Department of Energy, Material Science. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.<\/figcaption><\/figure>\n<p><strong>Grain-boundary strengthening<\/strong> (or Hall\u2013Petch strengthening) strengthens materials by changing their average crystallite (grain) size. The size of the grain determines the properties of the metal. For example, smaller grain size increases tensile strength and tends to increase ductility. Larger grain size is preferred for improved high-temperature creep properties. Decreasing the grain size also is an effective way to increase ductility. When grain size is reduced, there are more grains with a greater number of arbitrarily aligned slip planes for the dislocations in the grains. This provides more opportunity for some slips to occur in a stressed material. Grain boundaries act as an impediment to dislocation motion for the following two reasons:<\/p>\n<ol>\n<li>Dislocation must change its direction of motion due to the different orientations of grains.<\/li>\n<li>Discontinuity of slip planes from grain one to grain two.<\/li>\n<\/ol>\n<p>Thus, grain refinement provides an important means to improve strength, ductility, and toughness. Many other strengthening mechanisms are achieved at the expense of ductility and toughness. For many materials, the yield strength \u03c3 varies with grain size according to<\/p>\n<p style=\"text-align: center;\">\u03c3<sub>y<\/sub> = \u03c3<sub>y,0<\/sub> + k\/d<sup>x<\/sup><\/p>\n<p>In this expression, termed the <strong>Hall\u2013Petch equation<\/strong>, k is a constant, d is the average grain diameter, and \u03c3<sub>y,0<\/sub> is the original yield stress. Note that this equation is not valid for both very large (i.e., coarse) grain and extremely fine-grain polycrystalline materials.<\/p>\n<p>The synergistic effect of alloying elements and heat treatment produces a tremendous variety of microstructures and properties of steels.<\/p>\n<ul>\n<li><strong>Vanadium<\/strong>. Vanadium is generally added to steel to inhibit grain growth during heat treatment. Controlling grain growth improves the strength and toughness of hardened and tempered steels. The size of the grain determines the properties of the metal. For example, smaller grain size increases tensile strength and tends to increase ductility. Larger grain size is preferred for improved high-temperature creep properties.<\/li>\n<li><strong>Tungsten<\/strong>. Tungsten produces stable carbides and refines grain size to increase hardness, particularly at high temperatures. Tungsten is used extensively in high-speed tool steels and has been proposed as a substitute for molybdenum in reduced-activation ferritic steels for nuclear applications.<\/li>\n<\/ul>\n<\/div><\/div>\n<div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\">\n<div   id="8n9s8rpp6h"    class=\"su-accordion su-u-trim\"><div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>References:<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">Materials Science:\n<p>U.S. Department of Energy, Material Science. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.<br \/>\nU.S. Department of Energy, Material Science. DOE Fundamentals Handbook, Volume 2 and 2. January 1993.<br \/>\nWilliam D. Callister, David G. Rethwisch. Materials Science and Engineering: An Introduction 9th Edition, Wiley; 9 edition (December 4, 2013), ISBN-13: 978-1118324578.<br \/>\nEberhart, Mark (2003). Why Things Break: Understanding the World, by the Way, It Comes Apart. Harmony. ISBN 978-1-4000-4760-4.<br \/>\nGaskell, David R. (1995). Introduction to the Thermodynamics of Materials (4th ed.). Taylor and Francis Publishing. ISBN 978-1-56032-992-3.<br \/>\nGonz\u00e1lez-Vi\u00f1as, W. &amp; Mancini, H.L. (2004). An Introduction to Materials Science. Princeton University Press. ISBN 978-0-691-07097-1.<br \/>\nAshby, Michael; Hugh Shercliff; David Cebon (2007). Materials: engineering, science, processing, and design (1st ed.). Butterworth-Heinemann. ISBN 978-0-7506-8391-3.<br \/>\nJ. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.<br \/>\n<\/p><\/div><\/div><\/div><div   id="8n9s8rpp6h"    class=\"su-divider su-divider-style-dotted\" style=\"margin:15px 0;border-width:2px;border-color:#999999\"><\/div><\/div><\/div><div   id="8n9s8rpp6h"    class=\"su-divider su-divider-style-default\" style=\"margin:15px 0;border-width:2px;border-color:#999999\"><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\">\n<p>See above:<br \/>\nMetalworking<a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/metals-what-are-metals\/metalworking\/\" class=\"su-button su-button-style-flat\" style=\"color:#606060;background-color:#ffffff;border-color:#cccccc;border-radius:10px;-moz-border-radius:10px;-webkit-border-radius:10px\" target=\"_self\"><span style=\"color:#606060;padding:7px 20px;font-size:16px;line-height:24px;border-color:#ffffff;border-radius:10px;-moz-border-radius:10px;-webkit-border-radius:10px;text-shadow:0px 0px 0px #000000;-moz-text-shadow:0px 0px 0px #000000;-webkit-text-shadow:0px 0px 0px #000000\"><i class=\"sui sui-link\" style=\"font-size:16px;color:#5d5d5d\"><\/i> <\/span><\/a><\/p><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"parent":28845,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"generate_page_header":""},"_links":{"self":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/30161"}],"collection":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/comments?post=30161"}],"version-history":[{"count":1,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/30161\/revisions"}],"predecessor-version":[{"id":39558,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/30161\/revisions\/39558"}],"up":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/28845"}],"wp:attachment":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/media?parent=30161"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}