High Temperature Mechanical Behavior of SiCf/Ti-Al Composites
- PDF / 2,171,558 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 33 Downloads / 276 Views
HIGH TEMPERATURE MECHANICAL BEHAVIOR OF SiCf/Ti-Al COMPOSITES H.Y. CHOU*, S.C. YANG*, K.L. WANG*, C.I. CHEN* and S.E. HSU* * Materials R&D Center, CSIST, P.O. Box 90008-8, Lungtan, Taiwan, R.O.C.
ABSTRACT Titanium aluminide was reinforced by AVCO SCS-6 continuous SiC fibers in unidirectional or 00/+450/-450 direction to make SiCf/Ti-Al composites through hot-pressing of Ti and Al powder mixture. The toughness of the composites is greatly improved at room temperature. The typical tensile elongation is over 0.8%. The room temperature strength of the composite can be sustained up to about 7000C. The processes developed in this study have two merits: (1) Ti and Al powders instead of Ti-Al powder can be directly used as raw materials, and (2) the mechanical properties of composites can be tailored in a similar fashion as those of conventional composites. Introduction Titanium aluminide has recently gained much attention due to its relatively high melting point and some other attributes, such as high specific strength and good corrosion resistance [1,2]. However, the biggest drawback of the Ti-Al intermetallic compound is its brittle nature. Therefore, finding ways to improve the ductility is an important effort of alloy development. One of the approaches to toughen the Ti-Al intermetallic compound, in both ductility and strength, is to incorporate the SiC-continuous fibers into the Ti-Al matrix to form SiCf/Ti-Al composites [3,4]. In this work, an innovative process was developed for the fabrication of unidirectional and 0o0145o/0o plied SiCf/Ti-Al composites by hot-pressing Ti and Al powder mixture through a spontaneous reaction [51 to form the titanium aluminide matrix as stated our previoustest paper of this temperatures, paper are: (1)and to report results inof both[6].at The roomobjectives and at elevated (2) to the investigate themechanical formation of intermetallic compound matrix during hot-press process. Experiments Fibers used in this study were AVCO SCS-6 SiC fibers of a 143pm diameter with a double coated surface layer of 4pm thickness. The fibers were wound over a rotating drum and coated with an organic binder to form fiber tape [7]. The raw materials used to form the matrix of composite were titanium powder (3-51pm, >99.9%) and aluminum powder (-100 mesh, >99.9%) with a stoichiometric composition. An organic binder was added into the powder mixture to form a metal powder tape. The fiber tape (A) and metal powder tape (B) were stacked in an ABAB sequence with fiber reinforcement in unidirectional or 00/+450/-450 direction. The stacks were put into a
stainless steel case. After removing the binder by heating the unconsolidated laminates to 5000C for 4 hours, the case was degassed and vacuum-sealed. The case with laminates inside was heated to 9500C with a heating rate of 15oC/min., then hot-pressed at a pressure of 10000 psi. Tensile and bending specimens were prepared from consolidated composites along the unidirectional and 900 transverse direction for 00/+450/-450 reinforcement and
were tested from r
Data Loading...
