Austenitization is the first step of heat treatment preceding the isothermal quenching of ductile iron in austempered ductile iron (ADI)

manufacturing. Usually, the starting material for the ADI production is ductile iron with more convenient pearlitic matrix. In this paper we

present the results of research concerning the austenitizing of ductile iron with ferritic matrix, where all carbon dissolved in austenite must

come from graphite nodules. The scope of research includedcarrying out the process of austenitization at 900o

Cusing a variable times

ranging from 5 to 240minutes,and then observations of the microstructure of the samples after different austenitizing times. These were

supplemented with micro-hardness testing. The research showed that the process of saturating austenite with carbon is limited by the rate

of dissolution of carbon from nodular graphite precipitates.

The results presented in this paper are a continuation of the previously published studies. The results of hest treatment of ductile iron with

content 3,66%Si and 3,80% Si were produced. The experimental castings were subjected to austempering process for time 30, 60 and 90

minutes at temperature 300o

C. The mechanical properties of heat treated specimens were studied using tensile testing and hardness

measurement, while microstructures were evaluated with conventional metallographic observations. It was again stated that austempering

of high silicone ferritic matrix ductile iron allowed producing ADI-type cast iron with mechanical properties comparable with standard

ADI.

The results of experimental study of solid state joining of tungsten heavy alloy (THA) with AlMg3Mn alloy are presented. The aim of

these investigations was to study the mechanism of joining two extremely different materials used for military applications. The

continuous rotary friction welding method was used in the experiment. The parameters of friction welding process i.e. friction load and

friction time in whole studies were changed in the range 10 to 30kN and 0,5 to 10s respectively while forging load and time were constant

and equals 50kN and 5s. The results presented here concerns only a small part whole studies which were described elsewhere. These are

focused on the mechanism of joining which can be adhesive or diffusion controlled. The experiment included macro- and microstructure

observations which were supplemented with SEM investigations. The goal of the last one was to reveal the character of fracture surface

after tensile test and to looking for anticipated diffusion of aluminum into THA matrix. The results showed that joining of THA with

AlMg2Mn alloy has mainly adhesive character, although the diffusion cannot be excluded.

Ductile iron casts with a higher silicone content were produced. The austempering process of high silicone ductile iron involving different

austempering times was studied and the results presented. The results of metallographical observations and tensile strength tests were

offered. The obtained results point to the fact that the silicone content which is considered as acceptable in the literature may in fact be

exceeded. The issue is viewed as requiring further research.

The results of structure observations of Ni base superalloy subjected to long-term influence of high pressure hydrogen atmosphere at 750K

and 850K are presented. The structure investigation were carried out using conventional light-, scanning- (SEM) and transmission electron

microscopy (TEM). The results presented here are supplementary to the mechanical studies given in part I of this investigations. The

results of study concerning mechanical properties degradation and structure observations show that the differences in mechanical

properties of alloy subjected different temperature are caused by more advanced processes of structure degradation during long-term aging

at 850K, compare to that at 750K. Higher service temperature leads to formation of large precipitates of δ phase. The nucleation and

growth of needle- and/or plate-like, relative large delta precipitates proceed probably at expense strengthening γ" phases. Moreover, it can't

be excluded that the least stable γ" phase is replaced with more stable γ' precipitates. TEM observations have disclosed differences in

dislocation structure of alloy aged at 750K and 850K. The dislocation observed in alloy subjected to 750K are were seldom observed only,

while in that serviced at high stress and 850K dislocation array and dislocation cell structure was typical.

The results of studies of W-Ni-Co-Fe experimental alloy, with chemical composition assuring a possibility of producing Ni-based supersaturated solid solution are presented. The alloy was prepared from tungsten, nickel, cobalt and iron powders which were first mixed then melted in a ceramic crucible where they slowly solidified in hydrogen atmosphere. Next specimens were cut from the casting and heated at a temperature 950o C. After solution treatment the specimens were water quenched and then aged for 20 h at a temperature 300o C. The specimens were subjected to microhardness measurements and structure investigations. The latter included both conventional metallography and SEM observations. Moreover, for some specimens X-ray diffractometry studies and TEM investigations were conducted. It was concluded that quenching lead to an increase of tungsten concentration in nickel matrix which was confirmed by Ni lattice parameter increase. Aging of supersaturated solid solution caused strengthening of the Ni-based matrix, which was proved by hardness measurements. The TEM observation did not yield explicit proofs that the precipitation process could be responsible for strengthening of the alloy.