Wyniki wyszukiwania - BazTech

1

Influence of annealing on the microstructure of cast TiAl-based alloy

Lapin J., Pelachová T.

Journal of Achievements in Materials and Manufacturing Engineering

|

2014

|

Vol. 65, nr 2

53--60

EN

Purpose: The aim of the present work is to study the influence of annealing on the microstructure of cast TiAl-based alloy. Design/methodology/approach: Effect of annealing on the microstructure of cast Ti-46Al-8Ta (at.%) alloy was evaluated at temperatures ranging from 700 to 800°C. Fine grain convoluted microstructure of heat treated alloy consisted of small lamellar colonies of α2-Ti3Al (crystal structure D019) intermetallic phase within γ-TiAl (crystal structure L10) phase. Findings: Annealing leads to precipitation of α2 and τ(crystal structure B82) particles at the grain boundaries at the expense of the α2 laths. This process is connected with a depletion of the grain boundaries of Ti and Ta and formation of Al rich γ phase. Lattice parameter a of the γ phase decreases, c increases and aspect ratio c/a increases with increasing time and temperature of ageing. Research limitations/implications: The annealing leads to an increase of lattice parameters a and c and decrease of the aspect ratio c/a of both α2 and τ phases. Originality/value: This work present the effect of long-term annealing on microstructure stability and lattice parameters of coexisting phases in this alloy at temperatures ranging from 700 to 800ºC.

2

Effect of oxygen on the microstructure of annealed TiAl based alloy

Klimova A., Lapin J.

Archives of Materials Science and Engineering

|

2014

|

Vol. 70, nr 1

21--27

EN

Purpose: The aim of the present work was to investigate the effect of oxygen on the microstructure and Vickers hardness after annealing followed by free air cooling of cast Ti-48Al-2Nb-1Cr-0.2Si (at.%) alloy. Design/methodology/approach: The effect of oxygen on the microstructure of cast intermetallic TiAl-based alloy with nominal composition Ti-48Al-2Nb-1Cr-0.2Si (at.%) was studied after isothermal annealing at temperatures ranging from 1150 to 1320°C followed by free air cooling to room temperature. The samples for annealing were prepared from an ingot with an oxygen content of 400 wt. ppm and from cast turbocharger wheels with two different amounts of oxygen of 1000 and 1800 wt. ppm. Findings: While the microstructure of the alloy with the oxygen content of 400 wt. ppm changes from duplex one composed of lamellar α2+γand single phase γgrains to nearly lamellar with increasing annealing temperature, the microstructure of the annealed samples with oxygen content of 1000 and 1800 wt. ppm remains nearly lamellar within the studied temperature range. Research limitations/implications: The evolution of the Vickers hardness with the annealing temperature is discussed from the point of view of volume fraction of single phase γgrains. The effect of oxygen on the Vickers hardness of studied castings is described. Originality/value: The alloy was studied in the form of cast ingot and centrifugally cast turbocharger wheels with different amounts of oxygen. Alloying with Cr and Nb was selected for better ductility and oxidation resistance of the studied alloy.

3

High temperature deformation behaviour of a directionally solidified Ni3Al - based alloy

Wierzbiński S., Lapin J., Czeppe T.

Archives of Metallurgy

|

1999

|

Vol. 44, iss. 2

221-237