[Kovove materialy - Metallic materials]
    Wed - May 04, 2016 - 15:32 No. of hits : 720623 ISSN 1338-4252 (online) ISSN 0023-432X (printed)
© Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Bratislava, Slovak Republic

VOLUME 44 (2006), Issue 1

Effect of heat treatments on the microstructure and mechanical properties of directionally solidified multiphase intermetallic Ni-Al-Cr-Ta-Mo-Zr alloy
vol. 44 (2006), no. 1, pp. 1 - 11

The effect of heat treatments on the microstructure and mechanical properties of directionally solidified (DS) multiphase intermetallic Ni-21.9Al-8.1Cr-4.2Ta-0.9Mo-0.3Zr (in at.%) alloy was studied. Two-step solution annealing of DS alloy at 1373 K for 100 h and 1483 K for 2 h leads to dissolution of spherical α-Cr and needle-like γ´ (Ni3Al) precipitates within the β (NiAl) dendrites. In the interdendritic region, dissolution of Cr-based particles and formation of irregular shaped γ areas in the vicinity of dendritic-interdendritic interfaces were observed. During ageing at temperatures from 1223 to 1323 K the growth of spherical α-Cr and lath-shaped γ´ precipitates in the β dendrites was observed. In the interdendritic region, the ageing leads to intensive precipitation of lath-shaped α-Cr precipitates, formation of irregular shaped Cr-based particles and transformation of γ matrix (Ni-based solid solution) with γ´ precipitates to the γ´ matrix with needle-like γ precipitates. The studied heat treatments can be successfully applied to soften the DS alloy. All Vickers hardness values measured for specimens aged at 1273 and 1323 K are lower than those for DS samples. A linear relationship between the Vickers hardness and compressive yield strength is determined for DS and heat-treated (HT) specimens, which allows the mechanical properties of the alloy to be predicted from simple hardness measurements. Optimal combination of the yield strength, ultimate compressive strength and plastic deformation to fracture is achieved after ageing at 1323 K for 30 h.

Key words
nickel aluminides, Ni3Al, NiAl, microstructure, heat treatment, mechanical properties

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Full title of this journal is bilingual: Kovové materiály - Metallic Materials.
The official abbreviation in accordance with JCR ISI is Kovove Mater.

Article abstracts updated: 2016-05-03 13:14     
Articles in press revised: 2016-04-22 09:53    
Full text pdf uploaded: 2016-04-08 12:48   
Information updated: 2015-09-20 09:12  

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