Microstructural aspects of martensite transformation in coarse-grained Fe-31.1 pct Ni-0.02 pct C

1979 ◽  
Vol 10 (1) ◽  
pp. 109-112 ◽  
Author(s):  
J. R. C. Guimarães ◽  
J. C. Gomes
Keyword(s):  
Martensite Transformation ◽  
Coarse Grained

Martensite Transformation of Ultrafine Grained Austenite in Fe-28.5at%Ni Alloy

2006 ◽  
Vol 503-504 ◽  
pp. 913-918 ◽  
Author(s):  
Hiromoto Kitahara ◽  
Nobuhiro Tsuji ◽  
Yoritoshi Minamino
Keyword(s):  
Martensite Transformation ◽  
Lamellar Spacing ◽  
Alloy Sheet ◽  
Coarse Grained ◽  
Boundary Structure ◽  
Ultrafine Grained ◽  
Ni Alloy ◽  
Mean Grain Size ◽  
The Mean ◽  
Lamellar Boundary

Martensite transformation of the ultrafine grained (UFG) austenite fabricated by the accumulative roll bonding (ARB) process was studied. The Fe-28.5at.%Ni alloy sheet was severely deformed in austenite state by the ARB process up to 5 cycles. The ARB processed sheet had the ultrafine lamellar boundary structure. The mean lamellar spacing was 230 nm in the 5 cycles specimen. The sheets ARB processed by various cycles were cooled down to 77 K to cause the martensite transformation. Martensite transformation starting (Ms) temperature decreased with increasing the number of the ARB process. The Ms temperature of the ultrafine lamellar austenite in the 5 cycles specimen was 225 K, which was lower than that (247 K) of the conventionally recrystallized specimen with mean grain size of 22 μm. The martensite having characteristic morphologies appeared from the UFG austenite, although the martensite transformed from the coarse-grained specimen showed typical plate (or lenticular) morphology. The strength of the nano-martensite transformed from the UFG austenite was about 1.5 times higher than that of the UFG austenite, and it reached to 970 MPa.

scholarly journals Role of Reversed Austenite Behavior in Determining Microstructure and Toughness of Advanced Medium Mn Steel by Welding Thermal Cycle

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2127 ◽  
Author(s):  
Yunxia Chen ◽  
Honghong Wang ◽  
Huan Cai ◽  
Junhui Li ◽  
Yongqing Chen
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Significant Role ◽  
Heat Affected Zone ◽  
Martensite Transformation ◽  
Thermal Cycle ◽  
Retained Austenite ◽  
Coarse Grained ◽  
Reversed Austenite ◽  
Austenite Transformation

Reversed austenite transformation behavior plays a significant role in determining the microstructure and mechanical properties of heat affected zones of steels, involving the nucleation and growth of reversed austenite. Confocal Laser Scanning Microscope (CLSM) was used in the present work to in situ observe the reversed austenite transformation by simulating welding thermal cycles for advance 5Mn steels. No thermal inertia was found on cooling process after temperature reached the peak temperature of 1320 °C. Therefore, too large grain was not generated in coarse-grained heat-affected zone (CGHAZ). The pre-existing film retained austenite in base metal and acted as additional favorable nucleation sites for reversed austenite during the thermal cycle. A much great nucleation number led to the finer grain in the fine-grained heat-affected zone (FGHAZ). The continuous cooling transformation for CGHAZ and FGHAZ revealed that the martensite was the main transformed product. Martensite transformation temperature (Tm) was higher in FGHAZ than in CGHAZ. Martensite transformation rate was higher in FGHAZ than in CGHAZ, which is due to the different grain size and assumed atom (Mn and C) segregation. Consequently, the softer martensite was measured in CGHAZ than in FGHAZ. Although 10~11% austenite retained in FGHAZ, the possible Transformation Induced Plasticity (TRIP) effect at −60 °C test temperature may lower the impact toughness to some degree. Therefore, the mean absorbed energy of 31, 39 and 42 J in CGHAZ and 56, 45 and 36 J in FGHAZ were exhibited at the same welding heat input. The more stable retained austenite was speculated to improve impact toughness in heat-affected zone (HAZ). For these 5Mn steels, reversed austenite plays a significant role in affecting impact toughness of heat-affected zones more than grain size.

scholarly journals Behavior of Inelastic and Plastic Strains in Coarse-Grained Ti49.3Ni50.7(at%) Alloy Deformed in B2 States

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 741
Author(s):  
Dorzhima Zhapova ◽  
Victor Grishkov ◽  
Aleksandr Lotkov ◽  
Victor Timkin ◽  
Angelina Gusarenko ◽  
...  
Keyword(s):  
Martensite Transformation ◽  
Elastic Moduli ◽  
Inelastic Strain ◽  
Martensite Phase ◽  
Coarse Grained ◽  
Internal Stresses ◽  
Plastic Strains ◽  
Torsional Strain ◽  
Interphase Boundaries ◽  
B2 Phase

The regularities of the change in inelastic strain in coarse-grained samples of the Ti49.3Ni50.7 (at%) alloy are studied when the samples are given torsional strain in the state of the high-temperature B2 phase. During cooling and heating, the investigated samples underwent the B2–B19′ martensite transformation (MT); the temperature of the end of the reverse MT was Af = 273 K. It was found that at the temperature of isothermal cycles “loading-unloading” Af + 8 K, when the specimen is assigned a strain of 4%, the effect of superelasticity is observed. With an increase in the torsional strain, the shape memory effect is clearly manifested. It is assumed that the stabilization of the B19′ phase in unloaded samples is due to the appearance of dislocations during deformation due to high internal stresses at the interphase boundaries of the B2 phase and the martensite phase during MT. The appearance of dislocations during the loading of samples near the temperatures of forward and reverse MT can also be facilitated by the “softening” of the elastic moduli of the alloy in this temperature range. At a test temperature above Af + 26 K, the superelasticity effect dominates in the studied samples.

The Alteration of the Pore Spaces in Sandstones

1973 ◽  
Vol 31 ◽  
pp. 210-211
Author(s):  
R. E. Ferrell ◽  
G. G. Paulson
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
The Other ◽  
Coarse Grained ◽  
Depositional Fabric ◽  
Soluble Components ◽  
Scanning Electron ◽  
Shape And Size

The pore spaces in sandstones are the result of the original depositional fabric and the degree of post-depositional alteration that the rock has experienced. The largest pore volumes are present in coarse-grained, well-sorted materials with high sphericity. The chief mechanisms which alter the shape and size of the pores are precipitation of cementing agents and the dissolution of soluble components. Each process may operate alone or in combination with the other, or there may be several generations of cementation and solution.The scanning electron microscope has ‘been used in this study to reveal the morphology of the pore spaces in a variety of moderate porosity, orthoquartzites.

On the Origin of the Microscystalline Structure in Rapidly Solidified IN-100 Powder

1977 ◽  
Vol 35 ◽  
pp. 260-261
Author(s):  
J. M. Walsh ◽  
K. P. Gumz ◽  
J. C. Whittles ◽  
B. H. Kear
Keyword(s):  
The Other ◽  
Coarse Grained ◽  
Microcrystalline Structure ◽  
Routine Examination ◽  
Atomization Process ◽  
Centrifugal Atomization ◽  
Splat Quenching ◽  
Powder Particles ◽  
Dendritic Microstructures ◽  
Rapidly Solidified

During a routine examination of the microstructure of rapidly solidified IN-100 powder, produced by a newly-developed centrifugal atomization process1, essentially two distinct types of microstructure were identified. When a high melt superheat is maintained during atomization, the powder particles are predominantly coarse-grained, equiaxed or columnar, with distinctly dendritic microstructures, Figs, la and 4a. On the other hand, when the melt superheat is reduced by increasing the heat flow to the disc of the rotary atomizer, the powder particles are predominantly microcrystalline in character, with typically one dendrite per grain, Figs, lb and 4b. In what follows, evidence is presented that strongly supports the view that the unusual microcrystalline structure has its origin in dendrite erosion occurring in a 'mushy zone' of dynamic solidification on the disc of the rotary atomizer.The critical observations were made on atomized material that had undergone 'splat-quenching' on previously solidified, chilled substrate particles.

Observation by HVEM of the martensite transformation and the superconducting transition in Nb3Sn

1988 ◽  
Vol 46 ◽  
pp. 788-789
Author(s):  
M. A. Kirk ◽  
M. C. Baker ◽  
B. J. Kestel ◽  
H. W. Weber
Keyword(s):  
Thin Films ◽  
Low Temperature ◽  
Superconducting State ◽  
Martensite Transformation ◽  
Sputter Deposition ◽  
Diffusion Reaction ◽  
Solute Diffusion ◽  
Superconducting Transition ◽  
Twin Boundaries ◽  
Martensite Structure

It is well known that a number of compound superconductors with the A15 structure undergo a martensite transformation when cooled to the superconducting state. Nb3Sn is one of those compounds that transforms, at least partially, from a cubic to tetragonal structure near 43 K. To our knowledge this transformation in Nb3Sn has not been studied by TEM. In fact, the only low temperature TEM study of an A15 material, V3Si, was performed by Goringe and Valdre over 20 years ago. They found the martensite structure in some foil areas at temperatures between 11 and 29 K, accompanied by faults that consisted of coherent twin boundaries on {110} planes. In pursuing our studies of irradiation defects in superconductors, we are the first to observe by TEM a similar martensite structure in Nb3Sn.Samples of Nb3Sn suitable for TEM studies have been produced by both a liquid solute diffusion reaction and by sputter deposition of thin films.

The butterfly martensite nucleation in an iron and nickel alloy

1990 ◽  
Vol 48 (4) ◽  
pp. 906-907
Author(s):  
Q.Z. Chen ◽  
X.F. Wu ◽  
T. Ko
Keyword(s):  
Nickel Alloy ◽  
Ethyl Alcohol ◽  
Dislocation Structure ◽  
Martensite Transformation ◽  
Room Temperature ◽  
The Matrix

Some butterfly martensite nuclei were observed in an Fe-27.6Ni-0.89V-0.05C alloy. The alloy was austenitized at 1200°C for 1 hour. Some samples were aged at 850° C for 40 minutes and quenched in 10% brine at room temperature. All the samples were cooled in ethyl alcohol for martensite transformation.A nucleus in an unaged specimen is shown in Fig.1. The nucleus has certain contrast different from the matrix and is shaped like one wing of a butter fly martensite. The SADP of the circled region is measured to be: da=dh, and approximate to dγ(111) and dm(110) with ∠AOB = 55° . It is similar to [011]f.c.c and b patterns in the anglez ∠AOB and the ratio ra/rb, respectively. The SADP shows that the structure of the nucleus is between f.c.c and b.c.c. The dislocation structure within the nucleus is shown in Fig.2. Their Burgers vectors and line directions are also given in it. There are many long dislocations near it without dislocations piled up as shown in Fig.3.Long dislocations are closed at one end as an envelope.

Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)

1990 ◽  
Vol 48 (4) ◽  
pp. 928-929
Author(s):  
Wang Zheng-fang ◽  
Z.F. Wang
Keyword(s):  
Stainless Steel ◽  
Thermal Cycle ◽  
Secondary Phase ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
Test Environment ◽  
Fine Grained ◽  
Evaluation Test ◽  
Welding Thermal Cycle ◽  
Micro Analysis

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.

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