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Purpose The purpose of this study is to evaluate and compare the mechanical performance of FFF parts when subjected to post processing thermal treatment. Therefore, a study of the annealing treatment influence on the mechanical properties was performed. For this, two different types of Nylon (PA12) were used, FX256 and CF15, being the second a short fibre reinforcement version of the first one. Design/methodology/approach In this study, tensile and flexural properties of specimens produced via FFF were determined after being annealed at temperatures of 135°C, 150°C or 165°C during 3, 6, 12 or 18 h and compared with the non-treated conditions. Differential scanning calorimetry (DSC) was performed to determine the degree of crystallinity. To evaluate the annealing parameters’ influence on the mechanical properties, a full factorial design of experiments was developed, followed by an analysis of variance, as well as post hoc comparisons, to determine the most significative intervening factors and their effect on the results. Findings The results indicate that CF15 increased its tensile modulus, strength, flexural modulus and flexural strength around 11%, while FX256 presented similar values for tensile properties, doubling for flexural results. Flexural strain presented an improvement, indicating an increased interlayer behaviour. Concerning to the DSC analysis, an increase in the degree of crystallinity for all the annealed parts. Originality/value Overall, the annealing treatment process cause a significant improvement in the mechanical performance of the material, with the exception of 165°C annealed specimens, in which a decrease of the mechanical properties was observed, resultant of material degradation.

Titanium aluminides are used in the aeronautical and automotive field as an alternative material to manufacture critical components exposed to high temperatures and corrosive environments. These alloys due to its intermetallic structure exhibit some special properties such as low density, high strength, high stiffness, corrosion resistance, and creep resistance. When these components are manufactured, surface integrity is one of the most relevant parameters used to evaluate the quality of the parts. Severe surface integrity problems are reported in the literature, defects such as microstructural alterations, work hardening, residual stresses, surface cracks, among others induced by the cutting process. The surface and sub-surface alteration induced by machining are critical because it will affect the parts performance. Some parameters affect the quality of machined surface. In particular cutting parameters, cutting tools material, tool wear and material properties are the most frequently investigated. Experimental and empirical studies are presented mainly in order to understand the surface integrity induced by machining. This paper provides an overview of the problems associated with the machining process of various types of titanium aluminides. The cutting tools, machining parameters, as well as processing parameters employed to improve machinability and reduce surface defects in titanium aluminides are analyzed and discussed. Particular focus was given to turning and milling process of gamma titanium aluminides. Also, some of the optimal parameters for machining titanium aluminides are presented offering a compilation of the most relevant information from the first to the most recent works that analyze the different aspects that affect the machining of these alloys.