Effect of tool pin profiles on the properties of foamable precursor developed by friction stir processing

Abstract

The high-strength lightweight materials are commonly used in automotive industries. Foam is one such material that has a porous structure which makes it light but at the same time provides good absorbent of impact load. In recent years, friction stir processing (FSP) is commonly used for the development of foam. However, the quality of the foam developed mostly depends on the FSP parameters that control the distribution of foamable particles. Thus in this study, the impact of tool pin profiles and numbers of passes on the distribution of a foamable mixture of AA7075/TiH2 in the substrate has been investigated. The three different tool pin profiles, i.e. straight threaded cylindrical (STC), triangular (TR), and square (SQ) pins are used with 2, 4, and 6 number of FSP passes. It is observed that dispersion of TiH2/AA7075 particles in specimens produced with STC tool pin profiles is more uniform than that of TR and SQ pins, resulting in superior material stirring and flow. A significant reduction in particle clustering and improved mixture distribution has been observed in the STC pin profile. Vickers hardness test shows the SQ and TR pin profiles show higher hardness in the processed zone due to lower exposure of temperature. Microwave heating is used to heat the precursor for the development of foam. It is found that the foam developed by STC pin has superior compressive properties due to uniformly distributed small pores.