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1 Zeszyty Naukowe. Mechanika / Politechnika Opolska

1 2010

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Directional solidification - the method of structural modification of Ni3Al-B alloys

Malcharcziková J., Kursa M., Pohludka M.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2010

z. 97

20-20

For purpose of investigation of high purity materials Ni-22Al-1B and Ni-24Al-1B alloys (all in at.%) were prepared by melting of basic components in vacuum induction furnace. The cylinder castings were afterwards directionally solidified in two-phase super-kanthal resistance furnace working on Bridgman's method principle. Re-melting proceeded in corundum tubes with the apex angle at 1 550°C and at uniform rate 50 mm/h. The alloys fabricated by this way were crossly and longitudinally cut and the sections were used for determination of porosity, micro-hardness and for evaluation of micro-structure. The common feature of micro-structure of the both alloys was its coarseness. Further features of structure were different. Long parallel lines of mesh passed through the sections with 22 at.% Al. It was not observed in the sections with 24 at.% Al. B-rich phase was inside of these structures. Definite composition of phase is still determinating for reason of boron low sensitivity of many detection devices. Micro-hardness determination of the samples of both alloys was measured on micro-hardness tester FM-100 with automatic testing unit FM-ARS 900. Two types of measurement were carried out. The first on unetched samples. This value characterized sample as component. The second it was measured micro-hardness of structures presented on scratch patterns after their etching. Average values of matrix micro-hardness were about 270š20 HV 0.05. The B-rich phase had much greater values. It is assumed, that phase can cohesively strengthen these alloys. The last measurement carried out on the samples of both alloys was determination of their porosity. Resultant values were approximally 0.05š0.03%.