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Design of gating system is an important factor in obtaining defect-free casting. One of the casting defects is a porosity caused by internal shrinkage in solidification process. Prediction of the internal shrinkage porosity in the femoral stem of commercially pure titanium (CP-Ti) is investigated based on the gating system design. The objective of this research is to get the best gating system between three gating system designs. Three gating system designs of the femoral stem were simulated in an investment casting method. The internal shrinkage porosity occurs on the largest part and near the ingate of the femoral stem. The gating system design that has ingates cross section area: 78.5; 157; and 128.5 mm 2 has the least of the internal shrinkage porosity. This design has the most uniform solidification in the entire of the femoral stem. An experiment is conducted to validate the simulation data. The results of internal shrinkage porosity in the three gating system designs in the simulation were compared with the experiment. Based on the comparison, the trend of internal shrinkage porosity at the three gating system designs in the simulation agrees with the experiment. The results of this study will aid in the elimination of casting defect.

Magnesium and its alloy are known as biodegradable materials. Application of these materials especially as an implant material such as fracture fixation, cardiovascular stent and musculoskeletal. Characteristic modifications of these materials have been extensively done by some treatments. The objective of this paper is to review some treatments of the magnesium and its alloy to increase their characteristic as a biomaterial. In this paper, the treatments of magnesium and its alloy by coating, surface mechanical attrition treatment (SMAT) and shot peening were reviewed. Some properties were studied base on these treatments such as corrosion resistant, morphology, mechanical properties, wettability, and biocompatibility. Coating treatment by thermal oxidation improved both wear and corrosion resistant. SMAT resulted in grain size of nanometre in the topmost surface of magnesium. Surface roughness and wettability also increased on the SMATed specimen but its corrosion resistant decreased. Severe shot peening on magnesium for orthopaedic application should be studied intensively.

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Recently, a high number of bone fracture incidents per year urges researchers in developing megaprostheses as artificial body parts. However, the complicated design and requirements for this custom-made prostheses are the key challenge. In accordance, this study focused on the preparation steps of 3D-modelling and casting simulation for the fabrication of megaprostheses implant by vacuum centrifugal casting. The reconstruction steps of 3D-modelling were started by observing the medical image data (i.e. CT-scan images). As the 3D-modelwas ready, the gating system was designed by placing two mandible bone models as the casting part with sprue and ingates where the design was respected to the gating system design for centrifugal casting. Moreover, the variation of casting part position,numbers, shapes and dimensions of the ingate, as well as the total surface area of ingates (Si) was applied while creating the gating system designsfor casting simulation. Chemically Pure Titanium (CP-Ti) with the pouring temperature and time of 1700°C and 4s, respectively, were used as the parameters for casting simulation. The solidification test results showed that the shrinkage cavities tended to decrease in volumetric scale with increasing the total surface area of the ingates, while the casting part position, number, shape, and dimension of ingate showed the difference in effectivity of the solidification of molten metal on the shrinkage cavities formation.