Thixojoining has been developed for D2 and M2 tool steels. The suitable globular microstructure and excellent bonding quality are obtained through this work. Scanning electron microscopy (SEM) observation along the joint interfaces showed a smooth transition zone with no cracks. In addition, fracture surface of the shear test samples showed that the fracture mode was transgranular. Finally, based on obtained results, this method presented high quality joint with nonequilibrium diffusion interface. 1. Introduction AISI D2 and M2 steels have good strength and excellent resistance to wear as well as perfect toughness [1]. The cladding and coating form of these tool alloys as a multilayer structure is a new type composite improved both alloys properties and is suitable for chemical and mechanical conditions. In such conditions, because of high carbon content and high mechanical properties, conventional cladding methods are not applicable or need to huge equipment [2, 3]; therefore, Thixoprocessing is recommended as a good solution in comparison with the above mentioned. Due to rheological advantages of Thixotropic materials, various methods based on Thixoprocessing have been developed. Thixojoining process is a joining technique together with forming in Thixoprocessing category. Producing multimaterial functional components and minimizing the defects over the weld zone are considered as advantages of this technique in comparison with conventional joining methods [4, 5]. This work aimed to evaluate the novel idea to achieve additional information about the general characteristics of this type of joining. In this study, bonding of two AISI tool (i.e., M2 and D2) steels has been successfully performed and characterized. 2. Experimental Procedure Two steel grades, S600 (AISI M2) and K110 (AISI D2), were chosen in this research. These steels were used in as-received condition without any modifications. For steel grades, initial process to produce spherical particles is less needed compared to nonferrous alloys [6]. The present work aims to provide globular joining structure in semisolid state by employing AISI D2 and M2 tool steels via applying an approximately 1？MPa constant compressive stress at nil strength temperature [7, 8] of D2 and direct partial remelting in furnace with argon controlled atmosphere. The study is known as a new type of diffusion interfacial structure across the interface of the welded parts. The direct partial remelting experiment was performed using PLC controlled resistance furnace, and a protective atmosphere was produced by flowing
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