Browsing by Subject "hot isostatic pressing"
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Item Densification Behavior of SLS Processed Al2O3/Al Composite(1995) Rao, T. Srinvasa; Bourell, D.L.; Marcus, H.L.Production of structurally sound parts by any rapid prototype technique is essential, because fully functional features are necessary where application testing is required. In the present work, a powder blend of A1203/AI (3:1 by weight) was mixed with ammonium dihydrogen phosphate and subjected to selective laser sintering (SLS) using a C02 laser. An attempt has been made to increase the powder bed density by introducing vibration to the part cylinder. These SLS processed preforms were then subj ected to a secondary heat treatment in a hydrogen atmosphere and to hot isostatic pressing. Densification behavior of these Al20 3/Al composite preforms is discussed.Item Effect of Heat Treatment and Hot Isostatic Pressing on the Morphology and Size of Pores in Additive Manufactured Ti-6Al-4V Parts(University of Texas at Austin, 2017) Zhang, Bin; Ham, Kyungmin; Shao, Shuai; Shamsaei, Nima; Thompson, Scott M.Additive manufactured parts suffer from porosity, among other defects. The slit-shaped pores due to lack of fusion are the most detrimental to fatigue and mechanical properties. Their sharp edges generate severe stress concentration and serve as preferred sites for crack initiation. The sharp edges also have low formation energy of surface adatoms, increasing their tendency to spheroidize under elevated temperatures, such as during heat treatment (HT). In hot isostatic pressing (HIP), the combined action of high temperature/pressure also reduces the size of the pores. In this work, HT and HIP were performed on Ti-6Al-4V parts manufactured from laser-based powder bed fusion to investigate the effect of HT and HIP on morphology/size of pores. Using scanning electron microscopy combined with X-ray computed tomography, special attention is paid to the evolution of the shape of the pore1s under controlled exposures to elevated temperature during HT. The results will be used, in our subsequent work, to validate a phase field porosity evolution model based on density functional theory.Item Increasing Process Speed in the Laser Melting Process of Ti6Al4V and the Reduction of Pores During Hot Isostatic Pressing(University of Texas at Austin, 2017) Ahlers, D.; Koppa, P.; Hengsbach, F.; Gloetter, P.; Altmann, A.; Schaper, M.; Tröster, T.Additive manufacturing of titanium alloys has gained intensive attraction from industry and academia. Moreover, for additively fabricated parts consisting of Ti6Al4V, hot isostatic pressing (HIP), is widely used as a post treatment in order to increase the relative density of the built parts. However, one aspect which has rarely been addressed so far, is the increase of process speed, accompanied by a reduced relative density in the as-built condition and a subsequent hot isostatic pressing process to achieve the desired dense material. The approach here is to use the standard process route as described, but intentionally increase the process speed and accept a certain value of porosity. The focal objective of this study is the identification of a parameter-set with the highest potential for an increase of process speed and subsequently reduce the internal defects during the hot isostatic pressing process to achieve completely dense components.