On the Heterogeneous Equilibria relating to liquid phase in the iron-corner.
By thermal analysis and microscopic examination, the melting points and the structural constituents of iron rich Fe-Cr-Si alloys containing up to 33% Si and up to about 50% Cr were determined. These alloys used were made of electrolytic iron, low carbon ferro-chromium and refined silicon by means of 3KVA. high frequency induction furnace.
In this composition range, there lie five primary crystallization surfaces, on which α, δ, η, ε and ∑ phases crystallize out. The phase ∑ is the ternary compound based on the super lattice of FeCr. The δ and η phases are all proportionally miscible solid solutions of FeSi-CrSi and Fe₅Si₃-Cr₅Si₃. respectively. The η phase in the Fe-Si system is formed during cooling in solid by the peritectoid reaction α+δ→η, while in the ternary system, Fe-Cr-Si, this phase crystallizes out primarily on cooling from liquid.
The following three invariant reactions take place;
Melt+δ_??_η+α, 1182°, Melt+ε_??_η+α, 12100°; Melt+∑_??_ε+α, 1230° and these invariant points are at 7.5% Cr 21.0% Si, 25.5% Cr 17.0%Si and 30.5% Cr 15.5% Si, respectively.

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From zero to two percent of Mg, Si and Mn has been added singly to Al-Cu (4%) alloy, and the effect of these elements on the “Rückbildung” Phenomenon was investigated.
The results obtained may be summarised as follows:
(1) Amount of retrogression decreases gradually when the contents of Mg were increased.
(2) Addition of Si does not affect to the amount of retrogression of the alloy which has been previously aged at room temperature, but when the alloy has been previously tempered at 170° for 2 days, the same effect as Mg appeared.
(3) Mn has no essential effect on the “Ruckbildung” Phenomenon of this alloy neither previously aged nor tempered.

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Gas in aluminium and cast aluminium alloys, i.e. Silumin, Y alloy, and Lautal, was estimated by means of hot extraction porcess in vacuum.
It was found that the amount of gas in commercial aluminium was about 1.5 cc/100 grams and 2 or 3 times in aluminium alloys for casting.
The extracted gas is composed of 85_??_94% hydrogen and 4_??_8% CH₄, CO and CO₂ being almost absent.
Huge amount of gas in aluminium, which is frequently reported by different authors, is proved to be attributed to the surface contamination of the sample as is already pointed out by Steinhäuser.
A new method for obtaining the sample free from surface, contamination is proposed; the method consists in cutting out the sample with a clean saw and scraper, which are previously washed with benzene and alcohol and are heated by small gas flame.

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Various tests were carried out on aluminium light alloy clad sheets actually used in our country. From the test results, it is concluded that the clad layer needs not always adhere to the 10% standard. From the point of view of corrosion resistance, as far as the required strength is obtainable, the layer should, be as thick as possible. That is, even though the 10% standard layer increases to 12%, strength over 42kg/mm² can be obtained, and both 1m/m sheet with 6% layer and 0.8m/m sheet with 8% layer, have sufficient corrosion resistance. Therefore, sheets thicker than 0.8m/m are sufficient with 8% layer, but sheets thinner than 0.6m/m must at least have layer above the 10% standard.

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The duralumin wires which were “Rückbilden” ed and age-hardened again were compared with the ordinary age-hardened duralumin wires as to their properties. The result indicated that they were found to possess almost the same mechanical properties, but to differ decidedly in their chemical properties such as stress-corrosion and the quantity of gas generated by corrosion. Our inference is that a small measure of segregation took place in a part of the alloy which was subjected to the “Rückbildung” heat-treatment.

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The corrosion tests of mild steel, 15% Si iron, 13% Cr steel, 30% Cr steel and 18-8 Cr-Ni steel were carried out by dip method. The corrosion resistance was examined in 5_??_98% HNO₃ at 30_??_70° by measuring the weight loss for 10 hours, and the corrosion rate was expressed as g/m² hr.
The results obtained are as follows. (1) Mild Steel; the resistivity of mild steel against conc. HNO₃ is small. (2) 15%Si Iron; the resistivity is excellent, though this iron is slightly corroded in dil. HNO₃. (3) 13%Cr Steel; this steel is corroded in dil. HNO₃, but against 40_??_60% HNO₃ the resistivity is fairly, good, and in more conc. HNO₃ this steel is corroded slightly. (4) 30% Cr Steel; the resistivity of 30% Cr steel is excellent. (5) 18-8 Cr-Ni Steel; the resistivity of this steel is excellent, though this steel is slightly corroded in conc. HNO₃ at 70°

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Es ist festgestellt nach Oszillograme, daβ das Passivwerden der Bleianode in H₂SO₄ in zwei Stufe vor sich geht. Die erste Passivität wird von der primären Bedeckung von PbSO₄ verursacht; die zweite beruht auf die Abscheidung von Pb(SO₄)₂, das als die sekundäre anodische Reaktion in Lösung gelit, oder die von PbO₂, das Hydrolysenprodukt von Pb(SO₄)₂. Nach der zweite Passivierung sinkt der Strom allmählich ab, der, nach einiger Zeit steigt wieder auf mit gleichzeitiger O₂ Entwicklung. Im Bereich der gesuchten Säurekonz., 0.2_??_8.0n, tritt die Passivitat am spätesten bei 5.0n ein.

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