Objectives : This study evaluated the effect of the Ti condition (as-received and re-cast) on the mechanical properties, microstructure and fractography.
Materials and methods : Castings ( n = 6) with Ti in the as-received and once recast condition were made in a centrifugal casting machine using a high-purity argon gas. The ultimate tensile strength (UTS), proportional limit (PL) and elongation (EL) of the as-received specimens were evaluated in a universal testing machine at a crosshead speed of 1 mm/min. The fractured specimens were polished down for Vicker’s microhardness (VHN) measurement (100 g/15 s) from 25 μm below the cast surface, then at 50, 100, 200 and 500 μm. The microstructures of the alloys were also revealed. Scanning electron microscopy fractography (SEM) was undertaken for the fractured surfaces after testing. The data from the mechanical tests and hardness were subjected to Student t -test and a two-way repeated measures ANOVA, respectively. Tukey’s test was used for pairwise comparison ( α = 0.05).
Results : Higher UTS, PL and VHN and lower EL were observed for recast cp Ti. The microstructure was not influenced by the Ti condition and the SEM shows several transverse cracks on as-received cp Ti castings, on the other hand, fewer cracks can be observed in the outer surface of re-cast cp Ti.
Conclusions : Despite the likely increased contamination when cp Ti is a 100% re-casted, this does not seem to cause any detrimental changes in the mechanical properties of the cp Ti. Therefore, the re-cast of casting surplus can be another alternative to reduce the costs involved in the Ti castings.