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23.06.2010 17:06 -
Доклад изнесен и публикуван. Металофизика. Международна конференция в София
INFLUENCE OF Cr AND Mn ON SOLID PHASE REACTIONS
UNDER AGING OF CASTING AUSTENITE QUENCHING ALLOYS
OF THE Fe-Mn-Cr-C-N, Fe-Mn-Cr-C, Fe-Cr-Mn-C SYSTEMS
Dr.Eng.Bogomil Velicov Kolcv Institute of Metal Science, BAS , 67 Shipchenski prohod Str., 1574 Sofia, Bulgaria
Summary There are presented graphic results about the influence ofCr and Mn on the quantity of ferro-magnetic phase, resp. on solid phase reactions under "aging " of austenite quenching casting alloys of the Fe-Mn-Cr-C system which may contain or not contain nitrogen. Experrimental results confirm a previosly stated hypothesis about thermal metastability and its accompanying solid-phase reactions under the influence ofCr and Mn. 1. Itroduction Theoretical and experimental studies on aging of double and triple systems of non-ferrous and heavy metals and alloys are comparatively well presented and explained [1, 2]. Experimental stuff on founded alloys (nickel-free) of Fe-Cr-Mn-C system, containing and non -containing N (including some stainless deformable steels - below O,1%C) is uterrly insufficient to explain the characteristics of these processes. Probably this is the reason why there is no theory about this phenomenon. The reason may also be the smaller interest towards these alloys, resp. towards N-alloyed after the first studies of Dulis and co. [3]. Afterwards, developing Methods of gaseous counter-pressure treatment of materials reestablished the studies in the period after 1961-1968 (The authors studies began in 1967). This gave rise to studies on obtaining new N-containing alloys (HNS) in other countries as well, after two decades of hard work in Bulgaria. World congresses were held - France (1988), Germany (199O), Ukraine (1993), Japan (1995), Finland-Sweden (1998). Obtaining and research on new N alloyed founded alloys in Bulgaria began in 1967-68, research on aging of austenite-tempered founded alloys began as late as 1974-75. For unexplainable reasons studies on thermal instability are basically focused on austenite stainless of Crl8NMnl2 type after plastic deformation [3, 4]. This includes our institute [4]. The absence of experimental data about founded alloys containing 0-30%Cr, from 7-8 (even from 1%) up to 25-30%Mn, 0,3-4%C containing N and N free (including above equilibrium quantity) is the other reason for the difficulties in clarr fying the theoretical basis of processes connected with thermal metastability (aging) of austenite tempered non nickel founded alloys of the Fe-Cr-Mn-C-N, Fe-Mn-Cr-C, resp. Fe-Cr-Mn-C, Fe-Mn-C, Fe-Cr-MN-C, Fe-Cr-C-(N) systems. In [5] is stated a hypothesis, result of more than 20 years of studies on "aging" of austenite-tempered alloys with different component ratio in the systems : Fe-Cr-Mn-C-(N), Fe-Mn-Cr-C-(N), Fe-MN-C-(N), Fe-Cr-C-(N). We assume that Cr and Mn in Ni-free austenite tempered founded alloys are the basic elements which determine the character of thermal metastability processes. They form solid solutions of substitution (Cr is feritizator, Mn-austenitizator and austenite stabilizer). Togheder with solid solution forming elements of installstion (C, N austenitizators and austenite stabilisers) they define the character of solid phase reactions. Heating and cooling (aging) can be carried out without any release of magnetic phases as shown in [5] stainless steels and cast iron remain non magmetic (with decomposition, to ferro-magnetic phases) low alloyed and Cr free austenite-tempered founded alloys on magnetic base containing N and N-free. [5] shows that this is probably due to an eutectoid reaction. Cr and Mn influence on aging processes by shifting the eutectoid point lo the left or to the right under homogenization and opposite under release or decomposition of carbide , nitride carbonitride phases. In average- and high alloyed with Cr founded austenite tempered alloys processes are practically above - eutcctic and in Mn (Cr-frce) allovs - eutectic...
In [6] was proved that under aging of stainless steels of Crl8NMnl2 type in perlite like columns more Cr than Mn (5-7 times) is released. This is probably due to the smaller free energy of combining of Cr atoms with C and N atoms in comparison with the energy of combining of MVi with C and N. As a result the solid solution wich releases Cr faster than Mn, can be stabilized to a certain extent. Residual Mn and N are sufficient enough to maintain the non magnetic above-eutectic process. Cr not only constricts the g-area, but also changes the g / g + k boundary [5, 7]. Similar aging processes preserving the alloy"s non magnetism are observed in founded austenite-tempered alloys containing 0,l-3%C, 8-18%Mn, above 12-14% Cr, 0,08-1,5% N [5, 7]. The recorded disintegration to ferrite and cementite ferro-magnetic phases) iaMn steels of the Hatfield type [5-10], resp. the recorded solid phase reactions (y—>y residual + a + Me3C) as well as the stated in [5] hypothesis necessitated additional experimental stuff to prove [5]. The aim was to study the influence of Cr and Mn on solid phase reactions, characteristics, resp. on ferro-magnetic phase quantity in austenite-tempered founded alloys not containing N. The study of N-free alloys was imposed by the common idea that aging processes are determined by Cr and N. As a matter of fact in [15] it was proven that in alloys of the Fe-Mn-Cr-C system with Cr below 0,5-1% and N free there is a big range of variation of C as well as a solid-phase reaction similar to those in Hatfield steel C110Mnl3. 2. Experiumental procedure and results To clarify the influence of Cr and Mn chiefly in low and average Cr alloyed founded alloys there have been carried out studies on two basic series of founded austenite tempered Ni-free alloys. Those of the Fe-Mn-Cr-C-N system contain 3-4% Cr and those of the Fe-Mn-Cr-C system transforming into Fe-Cr-Mn-C system contain from 0,4 to 25-30% Cr. To this end ferro-magnetic phasefFMPh) has been measured. This phase is the most typical and certain indicator (along with X-ray phase analisis) for solid phase processes under heating and cooling of austenite-tempered alloys [15]. FMPh has been measured in a surface with 1,5 mm in radius and 1,5 mm deep. Hence, the ferritometer delivers information for FMPh in 7 mm3. When recording a ferrite phase in the range 50-100%, the measunnent accuracy is 8-10% i.e smaller. Current experiments recorded FMPh below 50%. The results of FMPh measurement by ferritoscope have been confirmed by X-ray structure analysis [15, 16]. Studies have been carried out on well polished metallographic laps 15 mm in diameter. Results have been shown graphically, where each point represents the average value of it least 5-6 measurements. In Fig. 1, 2 is shown the influence of Cr (Cr/C, Cr/C+N) and of Mn (Mn/C, Mn/C+N) on FMPh quantity after heating and cooling (aging) for 10 hours at 700°C of N containing alloys, Fig.3-5 show the influence of Cr ( 1,4 to 25%) on FMPh quantity, after aging for 10 hours at 500°C, 700°C- 900°C of founded N free austenite tempered alloys of the Fe-Mn-Cr-C system, resp. Fe-Cr-Mn-C system. Fig. 5, 6, 7 show Cr and Mn distribution in the solid solution and in the carbide phase resp. for alloys of the Fe-Mn-Cr-C and Fe-Cr-Mn-C-N systems [11-14]. Studies on dispersion needle-like phases are presented in Figs. 8-11. 3. Results analysis The results shown in Fig. 1-7 confirm the previoosly stated hypothesis [5]. Increasing Cr content resp. the reatios Cr/C, Cr/C+N, FMPh quantities decrease, unexpectedly at first glance. The reason is the predominant drovving out of Cr in comparison with Mn from newly released phases carbides, nitrides and carbonilridcs. Cr affinity to
words C and N and vice versa is higher than Mn affinity towards C and N when Cr and Mn coexistics are more favourable than those of Mn: quantity, diffusion coefficient, mobility, atomic characteristics free energy of combining with C and N, etc. This is how Cr can stabilize and austenize the solid solution. Fig.2 shows that increasing Mn content, resp. the ratios Mn/C, Mn/C+N, FMPh quantity after aging of founded austenite-tempered alloys of the Fe-Mn-Cr-C-N system containing ~ 3%Cr decreases. Unlike Cr, Mn rarely stabilizes the solid solution. Cr contains the release of Mn in the newly formed carbide, nitride and carbonitride phases. But still, Mn can be drown ouf in the form of cementite. The recorded small quantities of FMPh above 12-14% are result of the release and disintegration of ever diminishing quantities of a phase and of the release of ferromagnetic phases of (Fe Mn)3C, (FeMn)4N types. In other words it is proven that processes of heating and cooling ("aging") are carried out in time at respective temperatures accordings to the equilibrium condition diagrams [5, 7], forN-alloys there are no diagrams drawn-up yet. For the Fe-MN-Cr-C system, resp. Fe-Cr-Mn-C (above O,1%C) system there are no condition diagrams either. The exeception are some N alloyed and N free polithermal and isothermal sections [5, 7] and presumptive polythermal sections [5]. Cr influence is also proven in aging of founded austenite-tempered alloys of Fe-Mn-Cr-C system, resp. Fe-Cr-Mn-C system (Fig. 3-5) with different C content. Carbon is austenitisator and reduces the quantity of FMPh. Although a feritizator, Cr also leads to FMPh reduction because of its above stated functions. The figures show y boundary according to Cr and C contents. FMPh are: a (ferrite martensite and disintegration products, Me3C, Me4N). Predominant release of Cr in the cementite (carbide) phase is also observed in primary crystallization of alloys of Fe-Mn-Cr-C-N system [11]. During cast iron crystallization predistribution of Cr takes place. The better part of Cr is included in C phases. By the carbide analisis method predominant Cr concentrastion in cementite under primary crystallization in low Cr-alloyed cast iron (1-2) has been determined [12-14]. Interphase Cr distribution in high Cr alloyed founded allooys, steels and cast iron in Fe-Cr-Mn-C(N), Fe-Cr-C(N), Fe-Mn-Cr-C(N) systems has been practically not studied. Our research confirms that in Cr-alloyed founded alloys Cr is predominanttaly released in carbide phases in primary crystallization as well as in secondary pre-crystallization, i.e in solid-phase reactions due to aging of austenite-tempered alloys of the studied systems. Cr content 9,5-10% leads to the release of carbides of the Me3C, after which starts the release of Me7C3. This is connected with a break in Fig. 2. Under primary crystallization of Mn-alloys of Fe-Mn-C system Mn is concentrated in the carbide phase [5-7]. The above mentioned studies after heating and cooling (aging) confirm the fact that Mn is concentrated in the carbide phase under secondary Fe-crystallization processes too, Fig. 8-11. Since Cr and Mn are predominantly released in the carbide phases under primary crystallization and secondary processes of thermal treatment ("heating and cooling) and since Cr is contained in comparison with Mn in these processes when Cr is in considerable quantities, it is obvious that thermal metastability is due to and is determined by condition diagrams: degree saturation, composition, to pressure. We carried out metallography [15, 16], transmission electron microscopy on thin foils for the morphology of dispersion phases, electron difraction in order to determine the type of the crystal lattice and X-ray microanalisis, by energy dispersion analysis in a point in order to determine the phases composition. These analises (Fig. 8-11) showed that under quick cooling in water after homogenization followed by aging (300-700°C) in alloys of Fe-Mn-Cr-C and Fe-Mn-C-N systems containing low quantities of Cr (below 2-5%) are observed typical needle-like phases formed through a diffusion-free mechanism. Under slow cooling in a fumance they are absent and disintegration is observed [8]. Metallographic there are observed primary carbides (ledeburite and into the grains). Preferrable surface for formation of needles is the most dense part of the paskage illlj They are distributed in packages in angles multiple of 30% (%%), Fig. 8. The needles consist of Mn, Fe and
Cr where Mn is more than Cr. They are tube-like shaped with outer diameter O,5 u.m and wall thickness 1=0,2 mm. Most probably these are carbides of Me3C type with stoichiorrietry Fe6MnMC2O, hexagonal crystall lattice and parameters: a=55A, c=6.98A [17], It is possible in the course of the aging processe process the ratio Fe, Mn, Cr, to vary in fovour of Mn. Increasing C and N separately or together leads to making the tube walis thinner (outer 0=0,25u.m, l=belovv 0,lp.m, alloy C320CrMnl5). The packages increase and become thicker. Residual austenite sharply decreases. In N alloys part of the needls break. Cr and Mn quantity in primary carbides (ledeburite) and in secondary needles is higher than the quantity in the matrix (Fig. 8-11). In the needless remote from the ledeburitite Cr and Mn coptent is almost one and the same with that in the matrix (Fig. 10-11). Cr content is almost one and the same with that in the matrix (Fig. 10-11). Cr content in the remotest secondary needles and in the matrix is insignificant and disappears against C backround. This research on the type of the needle-like phases is confirmed by X-ray structure analysis [15, 16]. The quantity of defections dislocations and micro-duplicates on the plains {111} in austenite of a C320CrMnl5 alloy is higher than the quantity in a 200CrMnl5 alloy. The aging process takes place in the solid phase reaction according to the hypotheis in [5] (C=l,8-2%, 15%Mn, Cr
Summary There are presented graphic results about the influence ofCr and Mn on the quantity of ferro-magnetic phase, resp. on solid phase reactions under "aging " of austenite quenching casting alloys of the Fe-Mn-Cr-C system which may contain or not contain nitrogen. Experrimental results confirm a previosly stated hypothesis about thermal metastability and its accompanying solid-phase reactions under the influence ofCr and Mn. 1. Itroduction Theoretical and experimental studies on aging of double and triple systems of non-ferrous and heavy metals and alloys are comparatively well presented and explained [1, 2]. Experimental stuff on founded alloys (nickel-free) of Fe-Cr-Mn-C system, containing and non -containing N (including some stainless deformable steels - below O,1%C) is uterrly insufficient to explain the characteristics of these processes. Probably this is the reason why there is no theory about this phenomenon. The reason may also be the smaller interest towards these alloys, resp. towards N-alloyed after the first studies of Dulis and co. [3]. Afterwards, developing Methods of gaseous counter-pressure treatment of materials reestablished the studies in the period after 1961-1968 (The authors studies began in 1967). This gave rise to studies on obtaining new N-containing alloys (HNS) in other countries as well, after two decades of hard work in Bulgaria. World congresses were held - France (1988), Germany (199O), Ukraine (1993), Japan (1995), Finland-Sweden (1998). Obtaining and research on new N alloyed founded alloys in Bulgaria began in 1967-68, research on aging of austenite-tempered founded alloys began as late as 1974-75. For unexplainable reasons studies on thermal instability are basically focused on austenite stainless of Crl8NMnl2 type after plastic deformation [3, 4]. This includes our institute [4]. The absence of experimental data about founded alloys containing 0-30%Cr, from 7-8 (even from 1%) up to 25-30%Mn, 0,3-4%C containing N and N free (including above equilibrium quantity) is the other reason for the difficulties in clarr fying the theoretical basis of processes connected with thermal metastability (aging) of austenite tempered non nickel founded alloys of the Fe-Cr-Mn-C-N, Fe-Mn-Cr-C, resp. Fe-Cr-Mn-C, Fe-Mn-C, Fe-Cr-MN-C, Fe-Cr-C-(N) systems. In [5] is stated a hypothesis, result of more than 20 years of studies on "aging" of austenite-tempered alloys with different component ratio in the systems : Fe-Cr-Mn-C-(N), Fe-Mn-Cr-C-(N), Fe-MN-C-(N), Fe-Cr-C-(N). We assume that Cr and Mn in Ni-free austenite tempered founded alloys are the basic elements which determine the character of thermal metastability processes. They form solid solutions of substitution (Cr is feritizator, Mn-austenitizator and austenite stabilizer). Togheder with solid solution forming elements of installstion (C, N austenitizators and austenite stabilisers) they define the character of solid phase reactions. Heating and cooling (aging) can be carried out without any release of magnetic phases as shown in [5] stainless steels and cast iron remain non magmetic (with decomposition, to ferro-magnetic phases) low alloyed and Cr free austenite-tempered founded alloys on magnetic base containing N and N-free. [5] shows that this is probably due to an eutectoid reaction. Cr and Mn influence on aging processes by shifting the eutectoid point lo the left or to the right under homogenization and opposite under release or decomposition of carbide , nitride carbonitride phases. In average- and high alloyed with Cr founded austenite tempered alloys processes are practically above - eutcctic and in Mn (Cr-frce) allovs - eutectic...
In [6] was proved that under aging of stainless steels of Crl8NMnl2 type in perlite like columns more Cr than Mn (5-7 times) is released. This is probably due to the smaller free energy of combining of Cr atoms with C and N atoms in comparison with the energy of combining of MVi with C and N. As a result the solid solution wich releases Cr faster than Mn, can be stabilized to a certain extent. Residual Mn and N are sufficient enough to maintain the non magnetic above-eutectic process. Cr not only constricts the g-area, but also changes the g / g + k boundary [5, 7]. Similar aging processes preserving the alloy"s non magnetism are observed in founded austenite-tempered alloys containing 0,l-3%C, 8-18%Mn, above 12-14% Cr, 0,08-1,5% N [5, 7]. The recorded disintegration to ferrite and cementite ferro-magnetic phases) iaMn steels of the Hatfield type [5-10], resp. the recorded solid phase reactions (y—>y residual + a + Me3C) as well as the stated in [5] hypothesis necessitated additional experimental stuff to prove [5]. The aim was to study the influence of Cr and Mn on solid phase reactions, characteristics, resp. on ferro-magnetic phase quantity in austenite-tempered founded alloys not containing N. The study of N-free alloys was imposed by the common idea that aging processes are determined by Cr and N. As a matter of fact in [15] it was proven that in alloys of the Fe-Mn-Cr-C system with Cr below 0,5-1% and N free there is a big range of variation of C as well as a solid-phase reaction similar to those in Hatfield steel C110Mnl3. 2. Experiumental procedure and results To clarify the influence of Cr and Mn chiefly in low and average Cr alloyed founded alloys there have been carried out studies on two basic series of founded austenite tempered Ni-free alloys. Those of the Fe-Mn-Cr-C-N system contain 3-4% Cr and those of the Fe-Mn-Cr-C system transforming into Fe-Cr-Mn-C system contain from 0,4 to 25-30% Cr. To this end ferro-magnetic phasefFMPh) has been measured. This phase is the most typical and certain indicator (along with X-ray phase analisis) for solid phase processes under heating and cooling of austenite-tempered alloys [15]. FMPh has been measured in a surface with 1,5 mm in radius and 1,5 mm deep. Hence, the ferritometer delivers information for FMPh in 7 mm3. When recording a ferrite phase in the range 50-100%, the measunnent accuracy is 8-10% i.e smaller. Current experiments recorded FMPh below 50%. The results of FMPh measurement by ferritoscope have been confirmed by X-ray structure analysis [15, 16]. Studies have been carried out on well polished metallographic laps 15 mm in diameter. Results have been shown graphically, where each point represents the average value of it least 5-6 measurements. In Fig. 1, 2 is shown the influence of Cr (Cr/C, Cr/C+N) and of Mn (Mn/C, Mn/C+N) on FMPh quantity after heating and cooling (aging) for 10 hours at 700°C of N containing alloys, Fig.3-5 show the influence of Cr ( 1,4 to 25%) on FMPh quantity, after aging for 10 hours at 500°C, 700°C- 900°C of founded N free austenite tempered alloys of the Fe-Mn-Cr-C system, resp. Fe-Cr-Mn-C system. Fig. 5, 6, 7 show Cr and Mn distribution in the solid solution and in the carbide phase resp. for alloys of the Fe-Mn-Cr-C and Fe-Cr-Mn-C-N systems [11-14]. Studies on dispersion needle-like phases are presented in Figs. 8-11. 3. Results analysis The results shown in Fig. 1-7 confirm the previoosly stated hypothesis [5]. Increasing Cr content resp. the reatios Cr/C, Cr/C+N, FMPh quantities decrease, unexpectedly at first glance. The reason is the predominant drovving out of Cr in comparison with Mn from newly released phases carbides, nitrides and carbonilridcs. Cr affinity to
words C and N and vice versa is higher than Mn affinity towards C and N when Cr and Mn coexistics are more favourable than those of Mn: quantity, diffusion coefficient, mobility, atomic characteristics free energy of combining with C and N, etc. This is how Cr can stabilize and austenize the solid solution. Fig.2 shows that increasing Mn content, resp. the ratios Mn/C, Mn/C+N, FMPh quantity after aging of founded austenite-tempered alloys of the Fe-Mn-Cr-C-N system containing ~ 3%Cr decreases. Unlike Cr, Mn rarely stabilizes the solid solution. Cr contains the release of Mn in the newly formed carbide, nitride and carbonitride phases. But still, Mn can be drown ouf in the form of cementite. The recorded small quantities of FMPh above 12-14% are result of the release and disintegration of ever diminishing quantities of a phase and of the release of ferromagnetic phases of (Fe Mn)3C, (FeMn)4N types. In other words it is proven that processes of heating and cooling ("aging") are carried out in time at respective temperatures accordings to the equilibrium condition diagrams [5, 7], forN-alloys there are no diagrams drawn-up yet. For the Fe-MN-Cr-C system, resp. Fe-Cr-Mn-C (above O,1%C) system there are no condition diagrams either. The exeception are some N alloyed and N free polithermal and isothermal sections [5, 7] and presumptive polythermal sections [5]. Cr influence is also proven in aging of founded austenite-tempered alloys of Fe-Mn-Cr-C system, resp. Fe-Cr-Mn-C system (Fig. 3-5) with different C content. Carbon is austenitisator and reduces the quantity of FMPh. Although a feritizator, Cr also leads to FMPh reduction because of its above stated functions. The figures show y boundary according to Cr and C contents. FMPh are: a (ferrite martensite and disintegration products, Me3C, Me4N). Predominant release of Cr in the cementite (carbide) phase is also observed in primary crystallization of alloys of Fe-Mn-Cr-C-N system [11]. During cast iron crystallization predistribution of Cr takes place. The better part of Cr is included in C phases. By the carbide analisis method predominant Cr concentrastion in cementite under primary crystallization in low Cr-alloyed cast iron (1-2) has been determined [12-14]. Interphase Cr distribution in high Cr alloyed founded allooys, steels and cast iron in Fe-Cr-Mn-C(N), Fe-Cr-C(N), Fe-Mn-Cr-C(N) systems has been practically not studied. Our research confirms that in Cr-alloyed founded alloys Cr is predominanttaly released in carbide phases in primary crystallization as well as in secondary pre-crystallization, i.e in solid-phase reactions due to aging of austenite-tempered alloys of the studied systems. Cr content 9,5-10% leads to the release of carbides of the Me3C, after which starts the release of Me7C3. This is connected with a break in Fig. 2. Under primary crystallization of Mn-alloys of Fe-Mn-C system Mn is concentrated in the carbide phase [5-7]. The above mentioned studies after heating and cooling (aging) confirm the fact that Mn is concentrated in the carbide phase under secondary Fe-crystallization processes too, Fig. 8-11. Since Cr and Mn are predominantly released in the carbide phases under primary crystallization and secondary processes of thermal treatment ("heating and cooling) and since Cr is contained in comparison with Mn in these processes when Cr is in considerable quantities, it is obvious that thermal metastability is due to and is determined by condition diagrams: degree saturation, composition, to pressure. We carried out metallography [15, 16], transmission electron microscopy on thin foils for the morphology of dispersion phases, electron difraction in order to determine the type of the crystal lattice and X-ray microanalisis, by energy dispersion analysis in a point in order to determine the phases composition. These analises (Fig. 8-11) showed that under quick cooling in water after homogenization followed by aging (300-700°C) in alloys of Fe-Mn-Cr-C and Fe-Mn-C-N systems containing low quantities of Cr (below 2-5%) are observed typical needle-like phases formed through a diffusion-free mechanism. Under slow cooling in a fumance they are absent and disintegration is observed [8]. Metallographic there are observed primary carbides (ledeburite and into the grains). Preferrable surface for formation of needles is the most dense part of the paskage illlj They are distributed in packages in angles multiple of 30% (%%), Fig. 8. The needles consist of Mn, Fe and
Cr where Mn is more than Cr. They are tube-like shaped with outer diameter O,5 u.m and wall thickness 1=0,2 mm. Most probably these are carbides of Me3C type with stoichiorrietry Fe6MnMC2O, hexagonal crystall lattice and parameters: a=55A, c=6.98A [17], It is possible in the course of the aging processe process the ratio Fe, Mn, Cr, to vary in fovour of Mn. Increasing C and N separately or together leads to making the tube walis thinner (outer 0=0,25u.m, l=belovv 0,lp.m, alloy C320CrMnl5). The packages increase and become thicker. Residual austenite sharply decreases. In N alloys part of the needls break. Cr and Mn quantity in primary carbides (ledeburite) and in secondary needles is higher than the quantity in the matrix (Fig. 8-11). In the needless remote from the ledeburitite Cr and Mn coptent is almost one and the same with that in the matrix (Fig. 10-11). Cr content is almost one and the same with that in the matrix (Fig. 10-11). Cr content in the remotest secondary needles and in the matrix is insignificant and disappears against C backround. This research on the type of the needle-like phases is confirmed by X-ray structure analysis [15, 16]. The quantity of defections dislocations and micro-duplicates on the plains {111} in austenite of a C320CrMnl5 alloy is higher than the quantity in a 200CrMnl5 alloy. The aging process takes place in the solid phase reaction according to the hypotheis in [5] (C=l,8-2%, 15%Mn, Cr
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