Department of Materials Science & Metallurgy

Rob Wallach

Rob Wallach portrait

Senior Affiliate

MA University of Cambridge
MSc Queen's University of Canada
PhD University of Cambridge

+44 (0)1223 334330

Joining of Materials

Individual materials are becoming more specialized and are designed to optimize their performance for specific applications. However for most applications, these highly developed materials have to be joined to others in a manner that ensures a minimal loss in properties or performance. This requires developing new processes and/or the refinement of existing approaches. This forms the basis of my research which is focused on joining materials, generally advanced but not exclusively so, with the emphasis on modelling processes, joint formation and predicting the properties of materials after they are joined.

Diffusion bonding

Our work has focused on fundamental modelling of various processes and on devising a flux-free diffusion-based approach using gallium to join alloys with oxide films. This patent-protected approach has been proven for aluminium, stainless steel and nickel-base superalloys, and has been extended to joining metallic foams to solid metal components. Strengths matching the parent materials are attainable and as well as the fabrication of dissimilar metal joints.

Predicting the performance and modelling the reliability of lead-free soldered joints

Lead-free solders are replacing conventional tin-lead eutectic solder on environmental grounds. These new alloys are being evaluated (e.g. data on creep and fatigue properties) and likely failure mechanisms identified.

High-energy welding processes (electron-beam and laser welding)

We have modelled the microstructures and properties of laser and hybrid welds in structural and pipe-line steels. Existing models for predicting weld metal and heat affected zone microstructures, and the mechanical properties of laser welds in structural steels are being evaluated. This follows previous research on predicting the formability after laser welding automobile steels to aid lightweight car production.

Diffusion bonds between dissimilar metals (aluminium and titanium) showing excellent mechanical strength
Diffusion bonds between dissimilar metals (aluminium and titanium) showing excellent mechanical strength
  • H Assadi, AA Shirzadi & ER Wallach, "Transient liquid phase diffusion bonding under a temperature gradient: Modelling of the interface morphology" Acta Mater. 49, 31-39 (2001).
  • AA Shirzadi & ER Wallach, "To provide a non-chemical method to remove the surface oxide from various alloys to improve bonding, and coating processes." British Patent Application 2005, GB2380491; USA Patent Application 2003, 6,669,534 B2, 30
  • S Turan, D Turan, IA Bucklow & ER Wallach, "The effect of metal coating on the strength of capacitor-discharge joining of oxide ceramics" Key Eng. Mater. 264-268, 687-690 (2004).
  • P Moore, D Howse & ER Wallach, "Microstructure and properties of laser/arc hybrid welds and autogenous laser welds in pipeline steels" Sci. Technol. Welding Joining 9, 314-322 (2004).