Design World

  • Home
  • Technologies
    • ELECTRONICS • ELECTRICAL
    • Fastening • joining
    • FLUID POWER
    • LINEAR MOTION
    • MOTION CONTROL
    • SENSORS
    • TEST & MEASUREMENT
    • Factory automation
    • Warehouse automation
    • DIGITAL TRANSFORMATION
  • Learn
    • Tech Toolboxes
    • Learning center
    • eBooks • Tech Tips
    • Podcasts
    • Videos
    • Webinars • general engineering
    • Webinars • Automated warehousing
    • Voices
  • LEAP Awards
  • 2025 Leadership
    • 2024 Winners
    • 2023 Winners
    • 2022 Winners
    • 2021 Winners
  • Design Guides
  • Resources
    • Subscribe
    • 3D Cad Models
      • PARTsolutions
      • TraceParts
    • Digital Issues
      • Design World
      • EE World
    • Engineering diversity
    • Trends
  • Supplier Listings
  • Advertise
  • Subscribe

What methods are available to bond dissimilar metals for use in critical applications?

By Michelle Froese | July 19, 2022

Written by Jed Bothell, Vice President
Atlas UHV

Where many applications might allow for the use of mechanical bolting or an adhesive or sealant to bond two dissimilar metals, high-performance applications in aerospace, medical, cryogenic, and vacuum often require greater strength and longevity. Mechanical fasteners are ideal for several applications but are subject to cracking or corrosion, depending on the environment, and add weight to an assembly. Adhesives provide a solid bond at the beginning of use, but they typically degrade over time.

Bimetal components do not require bolting or the use of an adhesive. Advanced joining technologies enable engineers to reliably apply the ideal properties of one metal with those of another, offering an advantage in several industries, including the vacuum, cryogenic, and semiconductor sectors, as well as others.

Additionally, the process of joining certain materials, such as aluminum to other metals, is challenging. Its tenacious oxide surface protects it from rust-like oxidation, which is visible on iron and steel, preventing close metal-to-metal contact.

Fortunately, there are alternative methods for bonding dissimilar metals that ensure a solid bond.

The two most recognized methods are explosion bonding (or explosion welding) and diffusion bonding. Each one offers benefits and drawbacks, depending on the application. But both methods produce a molecular bond that out-performs mechanical bolting and adhesive bonding, which typically require upkeep and maintenance.

Explosion bonding or welding (EXW) is a solid-state process by which dissimilar metals can be joined together at an atomic level. Preparation for bonding requires that two plates lay flat against one another — a flyer plate on top of a base plate, separated by a small gap. An explosive charge is placed on the flyer plate and detonated from a point at the edge of the plates.

A controlled progressive ignition travels across the flyer plate much like ripples in a pond. The explosion accelerates the plates together with impact velocities of 1800 to 2200 m/sec. As a result, a high-energy surface plasma is formed between the plates, moving ahead of the collision point and stripping electrons from the two bonding surfaces.

The electron-hungry metals are then thrust together at extreme pressures, forming an electron-sharing bond.

Metals — such as copper, titanium, high-nickel alloys, and stainless steel — can easily be bonded through the EXW process. Typically, aluminum and stainless steel are incompatible and unable to bond directly, because of the formation of brittle intermetallic compounds.

However, technology is solving this challenge. One solution exploits the metallurgical compatibility from a multi-layered composition consisting of 316L stainless steel, copper, titanium, and 6061 T6 aluminum to provide a part with maximum hermeticity (or airtight), ductility, and an ability to cycle from cryogenic to high temperatures.

EXW is not always ideal. It depends on the final application. Depending on the bonding materials, explosive bonding typically requires a metal layer between the two primary metals, such as copper. This layer must be evaluated when producing a part because it also has characteristics that might affect the final application. For example, a copper substrate will add an electrically conductive layer to the end product.

Diffusion bonding is a process by which different metals are placed together at an extremely high pressure and heated to an elevated temperature for a specific duration. Bonding occurs in stages.

In the explosion bonding process, the EXW bond line separates the aluminum portion of a component from the stainless-steel part, as shown here.

First, the materials yield and creep in a way that the frictional force pushes waves of the now plastically deformed materials into a larger area of contact. Atoms that are in the contact area, then, diffuse and rearrange the grain boundaries of the two materials in such a way that it eliminates the original pores in the bonded area.

Finally, this diffusion dominates the area, forming a bond. It’s critical, however, that surface oxides are removed or displaced, which typically necessitates a vacuum environment.

It’s also important to note that diffusion bonding has machine limitations. This type of bonding depends on the strict control of bonding pressure, bonding temperature, the atmosphere, and the holding time. These conditions vary for bonding different materials. Aluminum stainless bonds are particularly challenging as a result of the formation of brittle intermetallic compounds, which can weaken the bond.

Additionally, thickness restrictions based on a machine’s size might create part size limitations. The joining of dissimilar metal parts requires a unique set of skills to properly machine the joined materials into a useable assembly. So, it’s important to work with reputable engineers or experts in the field.

A benefit of reliably bonded bimetallic joints is that these assemblies can be used to combine corrosion resistance, higher thermal conductivity, and several other properties not found in just one metal. With bimetallic joints, engineers can make a metallic composite material that enables them to attain the highest performance and maximum value.

 

You Might Also Like


Filed Under: Fastening + joining

 

LEARNING CENTER

Design World Learning Center
“dw
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, tools and strategies for Design Engineering Professionals.
Motor University

Design World Digital Edition

cover

Browse the most current issue of Design World and back issues in an easy to use high quality format. Clip, share and download with the leading design engineering magazine today.

EDABoard the Forum for Electronics

Top global problem solving EE forum covering Microcontrollers, DSP, Networking, Analog and Digital Design, RF, Power Electronics, PCB Routing and much more

EDABoard: Forum for electronics

Sponsored Content

  • Sustainability, Innovation and Safety, Central to Our Approach
  • Why off-highway is the sweet spot for AC electrification technology
  • Looking to 2025: Past Success Guides Future Achievements
  • North American Companies Seek Stronger Ties with Italian OEMs
  • Adapt and Evolve
  • Sustainable Practices for a Sustainable World
View More >>
Engineering Exchange

The Engineering Exchange is a global educational networking community for engineers.

Connect, share, and learn today »

Design World
  • About us
  • Contact
  • Manage your Design World Subscription
  • Subscribe
  • Design World Digital Network
  • Control Engineering
  • Consulting-Specifying Engineer
  • Plant Engineering
  • Engineering White Papers
  • Leap Awards

Copyright © 2025 WTWH Media LLC. All Rights Reserved. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media
Privacy Policy | Advertising | About Us

Search Design World

  • Home
  • Technologies
    • ELECTRONICS • ELECTRICAL
    • Fastening • joining
    • FLUID POWER
    • LINEAR MOTION
    • MOTION CONTROL
    • SENSORS
    • TEST & MEASUREMENT
    • Factory automation
    • Warehouse automation
    • DIGITAL TRANSFORMATION
  • Learn
    • Tech Toolboxes
    • Learning center
    • eBooks • Tech Tips
    • Podcasts
    • Videos
    • Webinars • general engineering
    • Webinars • Automated warehousing
    • Voices
  • LEAP Awards
  • 2025 Leadership
    • 2024 Winners
    • 2023 Winners
    • 2022 Winners
    • 2021 Winners
  • Design Guides
  • Resources
    • Subscribe
    • 3D Cad Models
      • PARTsolutions
      • TraceParts
    • Digital Issues
      • Design World
      • EE World
    • Engineering diversity
    • Trends
  • Supplier Listings
  • Advertise
  • Subscribe
We use cookies to personalize content and ads, to provide social media features, and to analyze our traffic. We share information about your use of our site with our social media, advertising, and analytics partners who may combine it with other information you’ve provided to them or that they’ve collected from your use of their services. You consent to our cookies if you continue to use this website.OkNoRead more