{"id":17264,"date":"2026-03-09T17:56:44","date_gmt":"2026-03-09T12:26:44","guid":{"rendered":"https:\/\/aluminiummagazine.com\/mag\/?p=17264"},"modified":"2026-03-15T11:46:37","modified_gmt":"2026-03-15T06:16:37","slug":"aluminium-4047-alloy-filler-wire-brazing-crack","status":"publish","type":"post","link":"https:\/\/aluminiummagazine.com\/mag\/aluminium\/aluminium-4047-alloy-filler-wire-brazing-crack.html","title":{"rendered":"Aluminium 4047"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><strong>The High-Silicon Specialist: Ultimate Crack Resistance for Demanding Joints<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In the family of <strong>aluminum<\/strong> filler metals, <strong>Aluminium 4047<\/strong> stands as the specialist&#8217;s choice for the most challenging welding and brazing applications. As the highest-silicon alloy in the 4000 series (typically 12% Si), 4047 offers the ultimate in crack resistance, fluidity, and low-temperature melting characteristics. While its more common cousin 4043 handles the vast majority of everyday <strong>aluminum<\/strong> welding, 4047 is the go-to solution when cracking persists, when brazing is required, or when the highest possible joint integrity is demanded.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This alloy represents the extreme end of the <strong>aluminum-silicon<\/strong> system, where the silicon content approaches the eutectic composition\u2014the point at which the alloy melts and solidifies at a single temperature rather than over a range. This unique metallurgical characteristic gives 4047 its exceptional performance in critical applications.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Composition and Metallurgy<\/strong>: Approaching the Eutectic<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Aluminium 4047<\/strong> is a 4000 series (<strong>Aluminum-Silicon<\/strong>) alloy with the highest commercially common silicon content. Its composition places it very close to the <strong>eutectic point<\/strong> of the system (12.6% Si), which fundamentally changes its solidification behavior.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Primary Composition:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Aluminum (Al):<\/strong> Balance (approx. 85\u201388%)<\/li>\n\n\n\n<li><strong>Silicon (Si):<\/strong> 11.0 \u2013 13.0% \u2014 The defining alloying element.<\/li>\n\n\n\n<li><strong>Iron (Fe):<\/strong> $\\le$ 0.8% \u2014 Controlled as an impurity.<\/li>\n\n\n\n<li><strong>Copper (Cu):<\/strong> $\\le$ 0.30% \u2014 Limited to low levels.<\/li>\n\n\n\n<li><strong>Beryllium (Be):<\/strong> $\\le$ 0.0003% \u2014 Added in trace amounts to some wire specifications to improve surface quality.<\/li>\n<\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>The Eutectic Advantage:<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The 12% silicon content gives 4047 a <strong>very narrow melting range<\/strong>\u2014approximately 577\u2013582\u00b0C (1070\u20131080\u00b0F). This near-eutectic composition means the alloy transforms from solid to liquid over a span of only 5\u00b0C, compared to 4043\u2019s 50\u00b0C range. This minimizes the &#8220;mushy zone&#8221; where solidification cracks typically form.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Core Properties<\/strong>: Engineered for Extreme Performance<\/h2>\n\n\n\n<ol start=\"1\" class=\"wp-block-list\">\n<li><strong>Superior Crack Resistance:<\/strong> The most valuable property of 4047 is its resistance to hot cracking. When 4043 occasionally fails on highly restrained joints, 4047 is the engineered solution.<\/li>\n\n\n\n<li><strong>Maximum Fluidity:<\/strong> This alloy has the <strong>highest fluidity<\/strong> of any common <strong>aluminum<\/strong> filler. The molten weld pool flows exceptionally well, penetrating into tight joints.<\/li>\n\n\n\n<li><strong>Low Melting Point:<\/strong> Requires less heat input to achieve fusion, which is vital for <strong>aluminum<\/strong> brazing where base metal melting must be avoided.<\/li>\n\n\n\n<li><strong>Moderate Strength with Low Ductility:<\/strong> 4047 offers higher tensile strength than 4043 but with <strong>significantly lower ductility<\/strong> (2\u20134% elongation). This makes the alloy unsuitable for parts requiring post-weld plastic deformation.<\/li>\n\n\n\n<li><strong>Anodizing Limitation:<\/strong> Like other high-silicon alloys, weld deposits will appear <strong>dark gray or black<\/strong> when anodized, contrasting with most <strong>aluminum<\/strong> base materials.<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Specifications and Physical Properties<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Aluminium 4047<\/strong> is manufactured to multiple international standards:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><td><strong>Standard<\/strong><\/td><td><strong>Designation<\/strong><\/td><\/tr><\/thead><tbody><tr><td><strong>AWS A5.10<\/strong><\/td><td>ER4047<\/td><\/tr><tr><td><strong>EN ISO 18273<\/strong><\/td><td>S Al 4047A (AlSi12(A))<\/td><\/tr><tr><td><strong>DIN 1732<\/strong><\/td><td>3.2585 (AlSi12)<\/td><\/tr><tr><td><strong>BS (UK)<\/strong><\/td><td>4047A (N21A)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Mechanical Properties (Typical)<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Density:<\/strong> ~2.66 \u2013 2.68 g\/cm\u00b3<\/li>\n\n\n\n<li><strong>Tensile Strength:<\/strong> 130 \u2013 210 MPa<\/li>\n\n\n\n<li><strong>Thermal Conductivity:<\/strong> ~160 W\/m\u00b7K<\/li>\n\n\n\n<li><strong>Electrical Conductivity:<\/strong> ~35% IACS<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Primary Applications<\/strong>: Where 4047 Excels<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1. Crack-Sensitive Joints<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Specific situations where 4047 is preferred include <strong>highly restrained joints<\/strong> where thermal contraction stresses are high and <strong>thick section welding<\/strong> where cooling rates are slower.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. Brazing and Braze Welding<\/h3>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/aluminiummagazine.com\/mag\/wp-content\/uploads\/2026\/03\/aluminum-4047-brazing-alloy-process-1024x576.jpg\" alt=\"aluminum 4047 brazing filler metal joining aluminum extrusion profiles\" class=\"wp-image-17328\" srcset=\"https:\/\/aluminiummagazine.com\/mag\/wp-content\/uploads\/2026\/03\/aluminum-4047-brazing-alloy-process-1024x576.jpg 1024w, https:\/\/aluminiummagazine.com\/mag\/wp-content\/uploads\/2026\/03\/aluminum-4047-brazing-alloy-process-300x169.jpg 300w, https:\/\/aluminiummagazine.com\/mag\/wp-content\/uploads\/2026\/03\/aluminum-4047-brazing-alloy-process-768x432.jpg 768w, https:\/\/aluminiummagazine.com\/mag\/wp-content\/uploads\/2026\/03\/aluminum-4047-brazing-alloy-process.jpg 1200w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><em>Aluminum 4047 alloy is commonly used as a brazing filler metal for joining aluminum extrusions.<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">4047 is the <strong>premier alloy for aluminum brazing<\/strong> due to its low melting point. It is widely used in:<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Furnace Brazing:<\/strong> For heat exchangers and evaporators.<\/li>\n\n\n\n<li><strong>Torch Brazing:<\/strong> For repair and small-scale production.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">3. Automotive and Casting Repair<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Heat Exchangers:<\/strong> Radiators and A\/C condensers are often brazed with 4047 clad on <strong>Aluminum 3003<\/strong> cores.<\/li>\n\n\n\n<li><strong>Casting Repair:<\/strong> The high silicon content matches the composition of common <strong>aluminum<\/strong> casting alloys like 356 and A356, making it ideal for filling defects.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Why Choose 4047?<\/strong> A Strategic Comparison<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><td><strong>Property<\/strong><\/td><td><strong>4043 (AlSi5)<\/strong><\/td><td><strong>4047 (AlSi12)<\/strong><\/td><td><strong>5356 (AlMg5)<\/strong><\/td><\/tr><\/thead><tbody><tr><td><strong>Silicon Content<\/strong><\/td><td>~5%<\/td><td><strong>~12%<\/strong><\/td><td>None<\/td><\/tr><tr><td><strong>Crack Resistance<\/strong><\/td><td>Good<\/td><td><strong>Superior<\/strong><\/td><td>Good<\/td><\/tr><tr><td><strong>Fluidity<\/strong><\/td><td>Good<\/td><td><strong>Excellent<\/strong><\/td><td>Moderate<\/td><\/tr><tr><td><strong>Ductility<\/strong><\/td><td>7-8%<\/td><td><strong>2-4% (Low)<\/strong><\/td><td>15-20% (High)<\/td><\/tr><tr><td><strong>Brazing Suitability<\/strong><\/td><td>Limited<\/td><td><strong>Excellent<\/strong><\/td><td>Not suitable<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>The &#8220;Step-Up&#8221; Strategy:<\/strong> Experienced <strong>aluminum<\/strong> welding engineers typically try 4043 first for general fabrication. If cracking occurs, they &#8220;step up&#8221; to 4047 to solve the issue.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Welding Guidelines<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Processes:<\/strong> Suitable for MIG (GMAW), TIG (GTAW), and brazing.<\/li>\n\n\n\n<li><strong>Shielding Gas:<\/strong> <strong>100% Argon<\/strong> is the standard; Argon\/Helium mixtures can be used for thicker <strong>aluminum<\/strong> sections.<\/li>\n\n\n\n<li><strong>Compatible Base Materials:<\/strong> 6xxx series (6061, 6063), 3xxx series (3003), and high-silicon casting alloys.<\/li>\n<\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Warning on Low Ductility:<\/strong> &gt; Because 4047 has very low elongation, it is unsuitable for joints subject to heavy impact, cyclic loading, or vibration. These welds will crack rather than stretch under strain.<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Sustainability and Recycling<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">As a specialized filler metal, 4047 contributes to sustainability by enabling <strong>lightweighting<\/strong>. Brazed <strong>aluminum<\/strong> heat exchangers are significantly lighter than copper-brass alternatives, directly reducing vehicle fuel consumption. Additionally, 4047 is fully recyclable within the existing <strong>aluminum<\/strong> scrap stream.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p class=\"wp-block-paragraph\"><em><strong>Aluminium 4047<\/strong> represents the pinnacle of the <strong>aluminum-silicon<\/strong> filler metal family. Its 12% silicon content delivers the ultimate in crack resistance and fluidity, making it indispensable for modern manufacturing. While its higher cost and low ductility limit it to specialized roles, in those situations\u2014from automotive radiators to aerospace fuel systems\u20144047 is often the only <strong>aluminum<\/strong> alloy that provides a reliable, leak-tight solution.<\/em><\/p><script>document.addEventListener(\"DOMContentLoaded\",function(){\n        if(window.innerWidth <= 768){\n            if (\"immediate\" === \"delay\") {\n                setTimeout(function(){document.querySelectorAll(\".pai-ad\").forEach(el=>el.style.visibility=\"visible\")},0);\n            } else if (\"immediate\" === \"scroll\") {\n                window.addEventListener(\"scroll\",function(){\n                    let s=window.scrollY\/(document.body.scrollHeight-window.innerHeight);\n                    if(s>0.1){\n                        document.querySelectorAll(\".pai-ad\").forEach(el=>el.style.visibility=\"visible\");\n                    }\n                });\n            } else {\n                document.querySelectorAll(\".pai-ad\").forEach(el=>el.style.visibility=\"visible\");\n            }\n        } else {\n            document.querySelectorAll(\".pai-ad\").forEach(el=>el.remove());\n        }\n    });<\/script>","protected":false},"excerpt":{"rendered":"<p>The High-Silicon Specialist: Ultimate Crack Resistance for Demanding Joints In the family of aluminum filler metals, Aluminium 4047 stands as the specialist&#8217;s choice for the most challenging welding and brazing applications. As the highest-silicon alloy in the 4000 series (typically 12% Si), 4047 offers the ultimate in crack resistance, fluidity, and low-temperature melting characteristics. While &#8230; <a title=\"Aluminium 4047\" class=\"read-more\" href=\"https:\/\/aluminiummagazine.com\/mag\/aluminium\/aluminium-4047-alloy-filler-wire-brazing-crack.html\" aria-label=\"Read more about Aluminium 4047\">Read more<\/a><\/p>\n","protected":false},"author":12,"featured_media":17265,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[721],"tags":[4111],"class_list":["post-17264","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-aluminium","tag-aluminium-alloys"],"_links":{"self":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/posts\/17264","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/comments?post=17264"}],"version-history":[{"count":0,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/posts\/17264\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/media\/17265"}],"wp:attachment":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/media?parent=17264"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/categories?post=17264"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/tags?post=17264"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}