There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Highly Reversible Zn Anode Enabled by Controllable Formation of Nucleation Sites for Zn-Based Batteries

The present article will describe aspects of the science and technology of titanium aluminide (TiAl) alloy system and summarise the low and high temperature mechanical and environmental properties exhibited by different alloy generations. In terms of processing developments, conventional gravity casting and near net shape casting would be discussed in detail. Also newer and non-conventional forging and additive manufacturing routes would be briefly highlighted. Extensive investigations of TiAl alloys have enabled their commercial implementation in aerospace and automotive industries. The GEnx™ engine is the first commercial aircraft engine that used TiAl (alloy 48–2–2) for their low pressure turbine blades. Among non GE engines, recently, new β-stabilised TiAl alloy (TNM) is being used to manufacture LPT blades for PW1100G™ engines. TiAl materials and design processes can reduce engine weight and improve engine performance.

TiAl alloys in commercial aircraft engines

Recent advances in zinc anodes for high-performance aqueous Zn-ion batteries

High temperature oxidation behavior and research status of modifications on improving high temperature oxidation resistance of titanium alloys and titanium aluminides: A review

Oxidation protective intermetallic Ti–Al–Cr–Y coatings of 10 μm thickness were deposited on specimens of the near-α alloy Ti-6242 and the (α + β) alloy Ti-17 using magnetron sputtering. The oxidation behaviour of the coated samples was studied at 600 °C and 700 °C under cyclic oxidation conditions in air. The coatings exhibited very good adhesion to the substrate materials and provided effective oxidation protection to the titanium alloys at both temperatures. A thin alumina scale formed on top of the coatings which showed a multi-phase microstructure consisting of the Ti(Cr,Al)2 Laves phase and, dependent on exposure temperature and time, the γ-TiAl, r-TiAl2 and/or AlCr2 phases.

Cyclic oxidation behaviour of the titanium alloys Ti-6242 and Ti-17 with Ti–Al–Cr–Y coatings at 600 and 700 °C in air

Intermetallic Ti-Al-Cr based coatings with small additions of yttrium or zirconium were deposited on the γ-TiAl alloys Ti-48-2-2 and TNM-B1 using magnetron sputtering. The oxidation behavior of the coated substrates was investigated in the temperature range between 850 °C and 950 °C under cyclic thermal exposure conditions in laboratory air. Excellent oxidation protection to both TiAl alloys was provided by the Ti-Al-Cr-Y coating in the studied temperature range for up to 1000 1 h-cycles. Similar results were obtained for the Ti-Al-Cr-Zr coating on the Ti-48-2-2 substrate. When thermally cycled at 900 °C and 950 °C, the latter protective layer deposited on the TNM-B1 alloy locally degraded probably caused by cracks in the coating leading to substrate oxidation. During high temperature exposure the microstructure of the coatings changed due to depletion in Al and Cr. Because alloy Ti-48-2-2 contains 2 at.% Cr and has a higher Al content compared to the TNM-B1 alloy, interdiffusion between coating and the Cr bearing substrate is reduced, retarding phase transformation in the oxidation protective layers.

Oxidation behavior of protective Ti-Al-Cr based coatings applied on the γ-TiAl alloys Ti-48-2-2 and TNM-B1

Effect of hydrogen carbonate and chloride on zinc corrosion investigated by a scanning flow cell system

Tension specimens of a γ-TiAl based TNM-B1 alloy (nominal composition in at%: Ti-435Al-4Nb-1Mo-01B) were coated with oxidation protective intermetallic Ti-Al-Cr layers containing yttrium and zirconium The coated specimens were tensile tested in air at room temperature (RT) and 850 °C in the as-deposited condition and after a pre-oxidation treatment at 850 °C for 300 h in air For comparison, uncoated specimens with and without pre-oxidation were also tested The elongation after fracture of the TNM-B1 alloy was 023% at RT; it increased to 83% at 850 °C The as-deposited coatings spalled off during tensile testing at RT No coating spallation was observed at elevated temperature and after pre-oxidation due to improved adhesion by interdiffusion bonding Pre-oxidation deteriorated the RT tensile properties of the γ-TiAl based alloy The RT ductility determined for pre-oxidized coated specimens was even more reduced probably caused by the brittleness of the coatings initiating premature cracks When tensile tested at 850 °C, the coated specimens exhibited considerably enhanced elongation after fracture in both the as-deposited and pre-oxidized conditions in comparison to the bare substrate alloy The increase in ductility was attributed to the high environmental protection of the substrate by the coatings

Nadine Laska

Papers

Cyclic oxidation behaviour of the titanium alloys Ti-6242 and Ti-17 with Ti–Al–Cr–Y coatings at 600 and 700 °C in air

Oxidation behavior of protective Ti-Al-Cr based coatings applied on the γ-TiAl alloys Ti-48-2-2 and TNM-B1

Effect of hydrogen carbonate and chloride on zinc corrosion investigated by a scanning flow cell system

Effect of intermetallic coatings on the tensile properties of a γ-TiAl based TNM alloy

Oxidation behaviour of a fluorinated beta-stabilized γ-TiAl alloy with thermal barrier coatings in H2O- and SO2-containing atmospheres