The use of titanium in production automobiles: Potential and challenges

Titanium offers a number of attractive features for use in high-production-volume automobiles; however, high cost has been a barrier to application, thus far. This article discusses the potential and challenges for the use of titanium in the family automobile. A.M. Sherman earned his Ph.D. in metallurgy at the Massachusetts Institute of Technology in 1972. He is currently senior staff technical specialist at Ford Motor Company. Dr. Sherman is a member of TMS. C.J. Sommer earned his B.S. in metallurgical engineering at University of Pittsburgh in 1982. He is currently manager of automotive marketing at Timet. F.H. Froes earned his Ph.D. in physical metallurgy at Sheffield University in 1967. He is currently the director of the Institute for Materials and Advanced Processes at the University of Idaho. Dr. Froes is also a member of TMS.     

Assessment of oxygen in silicon carbide fibres

Five different types of SiC fibre produced by chemical vapour deposition were analysed using Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and X-ray (WDX) analysis. Fibres studied include SCS0, SCS6, Sigma SM1240 and two types of SiC fibres denoted SAM1 and SAM2, produced in the Commonwealth of Independent States (Ukraine, former USSR). Fibres were fracturedin situ in the Auger spectrometer. For each fibre, the oxygen, carbon and silicon yields were measured and qualitative assessment of oxygen was performed. Results suggest that the SCS0 fibre contains less oxygen than other SiC fibres. It was revealed that the SAM1 fibre (120 m diameter) has a duplex SiC and carbon coating deposited over a 20 m tungsten core prior to the main SiC deposition, to decouple mechanically the tungsten core from the main SiC deposition.     

Deformation behavior of blended elemental ti-6ai-4v compacts

A blended elemental Ti-6A1-4V alloy powder, sintered to 99 pct theoretical density, was tested in tension and fatigue and characterized by optical, scanning, and transmission electron microscopy and by X-ray energy dispersive analysis. The microstructure consisted of a combination of equiaxed and low aspect ratio lamellar alpha phase. Two types of pores were observed: macropores at grain boundaries or triple points, and micropores within alpha regions. Chemical homogeneity was achieved within individual alpha or beta regions with slight compositional fluctuations between different grains. The deformation modes in alpha regions were investigated by transmission electron microscopy on thin foils prepared from tensile and cyclically deformed specimens. Tensile deformation occurred by homogeneous slip on both prismatic and pyramidal alpha slip planes. In cyclic deformation, on the other hand, little slip activity was found except for some heterogeneous slip on the basal plane associated with a relatively large micropore. Micropores of ?0.5 μm size were found to act as dislocation pinning sites.     

Mechanochemical processing of nanocrystalline Ti-6Al-4V alloy

Synthesis of nanocrystalline Ti-6Al-4V was explored using mechanochemical processing. The reaction mixture was comprised of CaH₂, Mg powder, anhydrous AlCl₃, anhydrous VCl₃, and TiCl₄. The milled powder (reaction product) primarily consisted of nanocrystalline alloy hydride having a composition (Ti-6Al-4V)H_1.942, along with MgCl₂ and CaCl₂ as by-products. Aqueous solutions of nitric acid, sulfuric acid, and 1 pct sodium sulfite were found to be very effective in leaching of the chlorides from the milled powder. The (Ti-6Al-4V)H_1.942 on dehydrogenation at 375°C resulted in nanocrystalline Ti-6Al-4V alloy powder.     

Processing and Deformation Behavior of Gamma TiAl Alloys with Fine-Grained Equiaxed Microstructures

This paper describes how a submicrocrystalline structure can be produced by isothermal deformation of cast and powder metallurgy -TiAl-based alloys at temperatures 1000°C and below using relatively inexpensive nickel-based superalloy die tooling. A detailed analysis of the effects of initial microstructure, chemical compositions, conditions of heat treatment and hot working on the formation of a homogeneous fine-grained microstructure in -TiAl-based alloys is presented.     

Thermochemical processing of titanium alloys

As the performance requirements of structures and devices increase, new and improved materials and processes are required. One such technique is thermochemical processing, which involves the use of hydrogen as a temporary alloying element. Thermochemical processing significantly enhances both the fabricability and mechanical behavior of titanium alloys.     

Rapidly solidified microstructure of AI-8Fe-4 lanthanide alloys

AI-817e and AI-8Fe-4RE (cerium, erbium, neodymium and gadolinium) alloys were rapidly solidified by the melt-spinning technique. The microstructure and phases of alloy ribbons were studied using optical metallography, SEM, TEM and X-ray diffraction techniques. The study has indicated that Re additions to AI-8Fe: (1) result in formation of an increased amount of fine microstructure region, (2) increase the hardness and stability, and (3) generally suppress the formation of needle-type Al₃Fe compounds by substituting them with globular Al₃Fe₂RE compounds. The addition of gadolinium appears to produce the best results.