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To characterise the bonding quality of semi-solid joined components, fundamental investigations were carried out by producing composite test specimens. By using steel as a semi-solid base matrix and different steel or copper alloys as inserted materials, an interesting field of material combinations was realised. Two different steel grades, the cold forming tool steel X210CrW12 and the bearing steel 100Cr6, were chosen as the material of the base matrix. Geometry variations were tested along with the variation of materials mentioned. The results supply information about the influence of the inserts shape on an early cooling of the base material during form filling or remelting of the insert caused by overheating. Qualitative and quantitative analyses of the mechanical characteristics of the bonding were carried out using mechanical tests. Metallographic analyses complete the description of the bonding mechanisms at the contact zone between the solidified matrix and the insert. The investigations on basic geometries show a good joining quality, which is mainly based on a strong force and form closure caused by contraction of the solidifying and cooling base matrix. In addition, material closure occurs in areas that are strongly heated during the joining process. These results provide key information for the design of prospective components of a new generation.

At the Institute of Metal Forming (IBF) current investigations within the framework of the Collaborative Research Centre 289 are mainly concentrated on forming of semi-solid precursor material of the steel grades X210CrW12 and 100Cr6. One important task is the precise temperature for the composition of solid and liquid phase fraction in the preheated billet. Experimental measurements and numerical simulations show significant heat losses during transport of the billet and after its insertion into the die. These developing temperature gradients influence strongly the resulting temperature field in the formed component. In case of the forming tools the critical increase of the temperature depending on the tool material is shown. As fundamental research in the field of thixojoining the temperature development of the inserts is analysed and demonstrates the feasibility of joining higher and lower melting materials into the semi-solid matrix.

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