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Chang S.-H.,National Taipei University of Technology | Huang K.-T.,National Siluo Agricultural Industrial High School | Liu C.-M.,Lunghwa University of Science and Technology
International Journal of Cast Metals Research | Year: 2011

The effect of hot isostatic pressing (HIP) temperature on mechanical properties of 713LC cast superalloy was investigated; three temperatures (1453, 1468, 1483 K) were tested for a HIP soaking time of 2 h and pressure of 150 MPa. HIP treatment at1453 K was found to be optimal. Extensive c9 precipitation was observed and the optimal HIP treatment decreased porosity by ̃57.1%. Under tension testing at a fast strain rate (0.001 s-1), the tensile strength was increased by 5.2% at room temperature, 9.8% at 813 K and 7.9% at 923 K, whereas at a very slow strain rate (0.0001 s-1), tensile strength was increased by 1.2% at room temperature and 7.8% at 813 K. © 2011 W. S. Maney & Son Ltd. Source


Chang S.-H.,National Taipei University of Technology | Lee S.-C.,National Cheng Kung University | Huang K.-T.,National Siluo Agricultural Industrial High School
Materials Transactions | Year: 2010

In our previous work, the parameters of solid-solution treatment for 718 alloy were discussed. The results showed that a solution temperature of 1020°C is optimum. The Laves and S phase can complete solution after 1020°C, 1 h solid-solution treatment. The aim of this study is to discuss the effect of various aging treatments for as-HIP treated 718 alloy. In the experiment, seven different aging treatments were used: 720°C for 2,4, 8 and 16h, furnace cooled to 620°C, soak for 8h, and air cooled to room temperature; 720°C for 8h, furnace cooled to 620°C, soak for 2,4,8 and 16 h, and air cooled to room temperature. Experimental results showed that 1020°C solid-solution, 720°C for 8 h and 620°C for 4h of aging treatment for as-HIP treated 718 alloy is optimum. AU the precipitations are MC carbides; the dimension of γ" precipitations is 30.41 nm, which with a maximum tensile strength (1407.2MPa) and elongation (14.5%) at room temperature. © 2010 The Japan Institute of Metals. Source


Chang S.-H.,National Taipei University of Technology | Lee C.-W.,National Taipei University of Technology | Huang K.-T.,National Siluo Agricultural Industrial High School | Wu M.-W.,National formosa University
Key Engineering Materials | Year: 2013

The experimental results indicated that the WC-12wt% Co specimens showed excellent mechanical properties and microstructure by the optimal sintering process. The G5 specimen sintered at 1400°C/1 h achieved a relative density of 98% and a hardness of HRA 88.5. Meanwhile, the TRS increased to 2400 MPa. F12 specimens that sintered at 1350°C/1 h achieved a relative density of 99% and a hardness of HRA 92.5. The TRS was also enhanced to 2170 MPa. In this study, the η phase (Co3W3C) precipitated at a high sintering temperature. The precipitations generated by liquid phase sintering gathered in some specific regions of the specimens and reacted with the WC particles. In addition, Co3W3C was a hard and brittle phase that resulted in a low TRS for the specimens; and a large amount of η phases were detrimental to the fracture toughness of the specimens. © (2013) Trans Tech Publications, Switzerland. Source


Chang S.-H.,National Taipei University of Technology | Chen S.-H.,National Taipei University of Technology | Huang K.-T.,National Siluo Agricultural Industrial High School
Materials Transactions | Year: 2012

Powder metallurgy is the conventional process for the production of CrCu alloys. Enhanced vacuum sintering techniques and the use of HIP processes can be applied to obtain higher densities and decreased porosity in the sintered parts. In this study, the optimal sintering process of Cr50Cu50 alloy targets is 1270°C for 1 h; a high density and low electrical resistivity of the alloy targets is obtained. The experimental results also indicate that the relative density of the Cr50Cu50 vacuum sintering targets can reach 99.42%, and that apparent porosity decreases to 0.54% after 1050°C at 175 MPa for 4 h of HIP treatments. The crystal property of sintered CrCu alloy is improved, and the resistivity decreased to 589 × 10 -8Ω.cm; IACS is also enhanced to 29.27% via HIP optimal treatment. This study shows that the high density and optimum properties of sintered Cr50Cu50 alloy targets can be produced by utilizing a suitable HIP treatment. © 2012 The Japan Institute of Metals. Source


Chang S.-H.,National Taipei University of Technology | Lee S.-C.,National Cheng Kung University | Huang K.-T.,National Siluo Agricultural Industrial High School | Liang C.,National Taipei University of Technology
Applied Mechanics and Materials | Year: 2012

The aim of this study is to explore alloy 718 that treated at an optimal HIP process, and then imposed various solid-solution temperatures and aging treatment. The experimental results indicated that Laves and δ precipitations obviously appeared within the grain boundary, under HIP treatment and lower solid-solution temperatures (940°C), which would result in poor mechanical properties. However, Laves and δ phase can be completely dissolved at 1020°C 1 hour solid-solution treatment. The tensile strength was increased to 1331.5 MPa, and elongation reached up to 6.1% under a 1020°C solid-solution and aging treatment. Increasing the solid-solution temperature to 1060°C would cause parts of the NbC to dissolve, thus a large number of the thin sheet-shaped NbC would appear in the solid-solution and aging specimen. The yield stress is slight increase, but a lot of NbC precipitations will result in the decreasing tensile strength (1298.8 MPa) and elongation (5.4%). As a result, the optimal solid-solution treatment parameter of alloy 718 is 1020°C for 1-hour. © (2012) Trans Tech Publications. Source

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