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Metallographic Evaluation

     High Energy Metals, Inc. has metallographic equipment which is used to evaluate the bond on a microscopic level.  The bond zone in an explosive weld is characterized by a wavy appearance.  This is due to the high-energy phenomena discussed in HEMI's Engineering and Design Basics.  If the bonding is performed using too much energy, melting and/or turbulence between the two (2) metals can occur leading to potential intermetallic formation and a possible brittle bond (Figure 2).  By observing the amplitude and periodicity of the wave pattern and contrasting it with the tested mechanical strength, HEMI has developed repeatable process procedures for many dissimilar metal systems.

 

  Figure 1. Aluminum/Tantalum/ Stainless

      Notice nice tight waves with little or no melting

  at the wave crests (100X)

Figure 2. Aluminum/Copper

      Notice intermetallic formation at the bond line

  This can lead to brittle mechanical properties (100X)

 

 

Figure 3. Aluminum/Tantalum /Inconel 718

      Very nice bond line formation. 

      Ram-tensile strength of the bond

      was >35,000 psi (62X)

 

Figure 4. Tantalum-10W /4340 Steel

      Near linear bond line. Good metallurgical

  bond with no melting observed. (200X)

 

Figure 5. Aluminum/Titanium /304L Stainless

      Very nice bond line formation.  Shear strength

  of the bond was >15,000 psi (40X)

 

  Figure 6. Tantalum-Tungsten Alloy / 4340 Steel

      Very nice bond line formation. 

  

Figure 7. Stellite/4340 Steel

      Very tight bond line formation.