Commission IX, incorporated in 1954 with the merging of the former commissions on weldability and brittle fracture, maintains its aim of the weldability of materials including the possible influences of welding on the integrity of welded joints and components during fabrication and service. This commission faces a challenge to expand its scope into the material behaviours subjected to additive manufacturing.

This commission continuously aims to get a better understanding of the relationship between composition and weld microstructure and between weld microstructure and properties in various alloys widely used in the industrial sector, namely high-strength steels, stainless steels and nickel-base alloys, creep-resistant alloys and non-ferrous alloys. The focus of Commission IX encompasses the various types of metals behaviour subjected to welding and the resulting influence on the integrity of welded joints and components during service. Strategically, weldability and the service integrity of joined components are regarded as interactions of the material with the introduced loading and the specific design. The scientific and technological work in Commission IX is focused on metallic materials, i.e. is based on the metallurgy of welded joints, covering their microstructure, properties and performance. Special emphasis is given to the occurrence and avoidance of imperfections, damages and failures during welding production and manufacturing, as well as during service of welded joints and components. These particularly include hot and cold cracking, high and low temperature, as well as aqueous and gaseous corrosion of welds, creep and fatigue. The Working Unit has four Sub-Commissions, focussing on the various steel types, CRAs and on non-ferrous metals, all having a respective working programme. Due to the large variety of metals and their interactions with the design and welding processes, the Commission collaborates with all other Commissions oriented towards welding processes or structural design.