The Dependence of Tensile Ductility on Investment Casting Parameters in Gamma Titanium Aluminides
- PDF / 2,028,624 Bytes
- 6 Pages / 408.96 x 639 pts Page_size
- 36 Downloads / 225 Views
placed on analysis of microstructure development, measurement of room temperature tensile properties and fractographic characterization. EXPERIMENTAL PROCEDURE A series of twelve investment cast plates with dimensions 10.2 cm x 10.2 cm x 12.7 mm (0.5 inch) were utilized in this study [1,2]. Investment mold preheat temperature and the degree of mold insulation were varied in order to influence cooling conditions. Three mold preheats temperatures, 315'C, 815'C and 1204'C, were used along with varying degrees of mold wrapping with Kaowool insulation. Following casting, all plates were subjected to a HIP cycle (hot isostatic pressing) of 1260 'C / 170 MPa / 4hrs. A summary of the mold preheat/wrap conditions is presented in Table I along with the range of estimated local solidification times between the surface and centerline of each plate. Mechanical testing was conducted using an Instron constant extension-rate tensile testing machine at nominal strain rates of 10 3/S. A total of thirty-one cylindrical tension specimens with a gage diameter of 4 mm and gage length of 19 mm were machined in accordance with low stress grinding procedures. Specimens were removed as close as possible from the plate surface in order to minimize possible incorporation of microstructural inhomogeneities at plate centerlines (Fig. 1). Three specimens were removed from each of the twelve plates, with the exception of plates 2, 5 and 11, where only one specimen was removed. In plates where only one specimen was taken (2, 5 and 11) the specimen position corresponds to the specimen labeled "3" in Fig. 1. After testing, fracture surfaces were characterized in a scanning electron microscope (SEM). Subsequently, in order to examine the microstructure in the vicinity of the fracture surface, each specimen was sectioned transKK2.1.1 Mat. Res. Soc. Symp. Proc. Vol. 552 © 1999 Materials Research Society
Table I. Mold preheat/wrap conditions and estimated cooling rates for 12.7 mm thick plates.
Plate Number
Alloy
Casting Conditions (Mold Preheat/Wrap Condition)
1
48-2-2
315 °C / Full Wrap
11-26
39
2
48-2-2
315 °C / Partial Wrap
10-25
39
3
48-2-2
815 °C / No Wrap
13 -30
55
4 5 6 7 8 9 10 11 12
48-2-2 48-2-2 Int. B Int. B Int. B XD TM XD TM XDTM XDNTM
1204 'C / Partial Wrap 1204 °C / Full Wrap 315 °C / No Wrap 815 °C / Partial Wrap 1204 C /Full Wrap 315 C /No Wrap 315 °C / Partial Wrap 815 °C / Full Wrap 1204 °C / No Wrap
20-44 186-222 10-24 13-31 202-235 13-21. 14-22 40-50 24-35
178 1097 35 60 1217 33 33 1284 125
Range of Local Solidification I
Time to 1125 °C (s) **
Time (s) *
XD is a registered trademark of Howmet Corporation. • Range indicates times at surface and centerline, respectively. ** Time between non-equilibrium solidus and binary eutectoid (1 125°C) temperatures.
Figure 1. Specimen location within the 12.7 mm thick investment cast plates.
versely below the fracture surface for further observation. These specimens were prepared metallographically and documented either with a light optical microscope or by SEM in
Data Loading...
