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Crystallisation and microstructure of low-silicon silumins with alloy additions

100%

Pietrowski S.

2011

tom Vol. 11, iss. 3

113-124

The paper presents the results of the analysis of crystallisation and microstructure of non-alloy silumins that contain: 2,0-6,0% of Si and alloy additions, approximately: 4,0% Ni, 4,0% of Cu and 0,5% of Mg, the knowledge of which is still very little. It has been proven that in non-alloy silumins, the increase of silicone concentration causes extending of crystallisation time of the eutectic mixture [...] and refinement of \alfa phase dendrites. It also causes the increase of the temperature of crystallisation of the eutectic mixture [...]. Alloy additions: Ni, Cu and Mg decrease by approximately 30 C the liquidus and solidus temperatures of silumins and extend the time of their crystallisation by around 100 sec. in comparison with non-alloy silumins. It is caused by crystallisation of additional phases Al3NiCu, Mg2Si and Al2Cu. Nickel, copper and magnesium refine the microstructure of castings.

Theodosius II’s solidus from Prełuki, Sanok County in material and traseological examinations

100%

Biborski M. , Biborski M.

tom LIV

285-292

The aim of the analysis of Theodosius’ II solid was to determine the chemical compounds of the coin alloy and to conduct a traseological analysis. The results show that the fineness of gold of which the coin was made was very high (obverse: 99,16% which means 23,8 karat gold and reverse of 99,20% which constitutes for the 23,81 karat gold), and the alloy metal was silver (0,65% and 0,62%). Traseological analysis has shown, that the hole in the lower part of the obverse, 2,1 mm in the diameter, was drilled with a very sharp, narrow, conical tool, the marks of which are still visible on the inside of the hole. Also, some traces of work concerning the coin’s die have been spotted. The engraving of the die was done gradually. Traces of consequent scratching with a graver are well visible both on the obverse and reverse. The character of places where sharp edges framing letters and some images are preserved serve proof of those being prepared with the use of a narrow, triangular-ended graver. All this suggests, that the maker of the die had a developed set of technical and artistic skills.