The Flexural Strength and Fracture Toughness of TC4-Based Laminated Composites Reinforced with Ti Aluminide and Carbide
TiC–Ti–Al mixed powders and TC4 titanium alloy foils were overlapped layer-by-layer in the graphite die. The TC4-based laminated composite sheets reinforced by Ti aluminide and carbide were successfully fabricated via spark plasma sintering (SPS) at 1100 °C with a well-bonded interface. The composite layers were mainly composed of TiAl, Ti3Al, Ti2AlC, and Ti3AlC2 phases. The carbides particles distributed in the matrix played an important role in the deflection of cracks and the passivation of microcracks. TC4 titanium alloy layers had an obvious effect on the stress distribution during the loading process, and provided an energy dissipation mechanism, which could improve the mechanical properties of the laminated composite sheets obviously. When the theoretical amount of Ti2AlC was 20 wt %, the flexural strength and fracture toughness of the laminated composite sheets reached the maximum value in the arrester direction, which were 1428.79 MPa and 64.08 MPa·m1/2, respectively.
Strengthening and toughening of laminated TiAl composite sheets by titanium alloy layers and carbide particles
Abstract Laminated sheets with Ti2AlC/TiAl composite layers synthesized from the Ti–Al–TiC system and TC4 titanium alloy as the toughening layer were fabricated by spark plasma sintering. Their phase composition and microstructure were analyzed and flexural strength and fracture toughness measured. The composite layers mainly comprised Ti2AlC, TiC, TiAl, and Ti3Al phases. The flexural strength and fracture toughness of the sheets perpendicular to the laminated direction were 455.74 MPa and 21.65 MPa · m1/2, respectively. The TC4 layers provided a strengthening–toughening effect by changing the crack propagation model and weakening the fracture energy. Ti2AlC particles provided a strengthening effect. The synergistic effect of the two components enhanced the mechanical properties of these TiAl-based laminated composite sheets.
Ethics and the Treatment of the Mentally Ill, Homeless Person: a Perspective on Psychiatry Resident Training
ObjectiveThe authors outline the unique ethical challenges that psychiatry residents face in working with individuals who are homeless and mentally ill. The authors also propose steps to develop effective teaching methods with residents working with these patients.MethodsThe authors reviewed literature relevant to the training of psychiatry residents in ethics and treating individuals who are homeless and mentally ill.ResultsThe authors summarize current literature and, with the use of case examples, provide guidelines for effective teaching.ConclusionsTeaching psychiatry residents who are working in the community with individuals who are mentally ill and homeless needs to address a number of unique ethical conflicts that arise in this area. The authors outline approaches to this teaching.