Influence Of Prior Deformation Research Articles

The influence of prior deformation on phase composition and strength properties of austenitic stainless steel in ion-plasma treatment

The influence of prior deformation on phase composition and strength properties of austenitic stainless steel in ion-plasma treatment

Modelling of the Influence of Prior Deformation of Austenite on the Martensite Formation in a Low-Alloyed Carbon Steel

The current work aims at developing models supporting design of the rolling and quenching processes. This requires a martensite formation model that can account for effect of previous plastic deformation as well as evolution of stress and temperature during the quenching step. The effect of deformation prior to the cooling on the transformation is evaluated. The experimental result shows that prior deformation impedes the martensite transformation due to the mechanical stabilisation of the austenite phase. Larger deformation above 30 % reduces the effect of the mechanical stabilisation due to increase in martensite nucleation sites. The computed transformation curves, based on an extended version of the Koistinen-Marburger equation, agree well with experimental results for pre-straining less than 30 %.

Aging of Copper-Titanium Dilute Alloys in Hydrogen Atmosphere: Influence of Prior-Deformation on Strength and Electrical Conductivity

The influence of prior-deformation on the mechanical and electrical properties of Cu-4.2 mol% Ti alloys aged in a hydrogen pressure of 0.8 MPa was examined. This follows from the results of aging solution-treated Cu-Ti alloys in a hydrogen atmosphere, which significantly improved their electrical conductivity over alloys conventionally aged in vacuum, without degradation of the mechanical strength. The maximum-strength was enhanced in the prior-deformed specimen, and the strengthening and increase in electrical conductivity were accelerated during aging in a hydrogen atmosphere, compared to that for the non-deformed specimen. As a result, the balance between the strength and the conductivity is improved within shorter aging time for specimens that are more severely deformed and then aged in a hydrogen atmosphere. The strengthening is mainly due to age-hardening by the growth of finely dispersed precipitates of Cu4Ti and TiH2, which are preferentially nucleated at lattice defects such as dislocations and nano-sized deformation twins. The improved conductivity is closely related to reduction of the solute Ti concentration in the copper matrix, which is attributed to the precipitation of TiH2 and Cu4Ti. Thus, prior-deformation assists to render a good combination of strength and electrical conductivity for Cu-Ti dilute alloys during aging in a hydrogen atmosphere.

Effect of Prior Cold-Working on Strength and Electrical Conductivity of Cu-Ti Dilute Alloy Aged in a Hydrogen Atmosphere

Aging solution-treated Cu-Ti alloys in a hydrogen atmosphere significantly improved their electrical conductivity without degradation of the mechanical strength, compared to conventionally aged alloys. In this study, the influence of prior deformation on the mechanical and electrical properties of Cu-4.2 at.% Ti alloys aged in a hydrogen atmosphere was examined. The Vickers hardness of the solution-treated specimen increased from 127 kgf/mm2 to 265 kgf/mm2 by aging at 673 K for 180 h in a hydrogen atmosphere of 0.8 MPa, while that of the deformed specimen achieved a maximum of approximately 280 kgf/mm2 by aging for 100 h in the same atmosphere. Prior deformation resulted in a more rapid increase in conductivity during aging than that without deformation. The conductivity at the peak-hardness of the deformed specimen was 22% IACS (International Annealed Copper Standard), which exceeded that for the solution-treated specimen. Thus, prior deformation assisted in a significant improvement of the mechanical and electrical properties during aging in a hydrogen atmosphere.

Multiscale Characterisation of the Transformation Texture in a High Performance Steel

The orientation relationships operating during the austenite (FCC) to BCC phase transformation were investigated in a high performance steel using X-ray and electron diffraction techniques and employing several length scales. These steels contain some retained austenite that permits the direct comparison of the textures of the parent (austenite) and product (ferrite, bainite, martensite) phases. X-ray diffraction allowed the global texture of the rolled parent austenite phase to be determined as well as that of its transformation product. EBSD techniques permitted study of the orientation relationships on a local scale. The observed correspondence relations are expressed in Rodrigues-Frank space. The exact Kurdjumov-Sachs relation was never found. The local spread of orientation in the parent austenite (due to deformation) is seen to be inherited by the bainite. This is attributed to the displacive mode of transformation to bainite. The influence of prior deformation of the austenite on the occurrence of variant selection was also studied. It appears that a critical strain is necessary to produce a significant amount of variant selection.

Pre‐necking and post‐necking relaxation and creep behavior of polycarbonate: A phenomenological study

AbstractExperiments have been performed to investigate the mechanical response of unfilled polycarbonate vis‐à‐vis the influence of prior deformation on stress relaxation and creep. Piecewise linear deformation histories, which involve strain‐controlled tensile loading of a specimen to a maximum load and partial unloading to a target strain/stress point as prologue to a relaxation test, have been shown to qualitatively influence the recorded stress‐time behavior. In particular, the stress magnitude during relaxation first increases and is then followed by a decrease. Analogously, in creep tests during unloading, the strain might decrease and then increase. Time characteristics for this U‐turn in the deformation response are influenced by the placement of the test. The influence of prior specimen conditioning on this phenomenon is investigated by comparing test data from virgin samples to that of specimens having high (∼85%) inelastic strain from prior tensile elongation. Findings suggest that the observed persistence in the occurrence of this reversal effect for both types of specimens is evidence of the need to incorporate this behavior into the fold of material modeling. Additionally, this novel relaxation and creep behavior has been observed in other amorphous (poly(phenylene oxide)) and crystalline (high‐density polyethylene) polymers. Polym. Eng. Sci. 44:1783–1791, 2004. © 2004 Society of Plastics Engineers.

Influence of prior deformation on the age hardening of a phosphorus-containing Cu–0.61wt.%Cr alloy

A copper alloy containing 0.61 wt.% Cr and 0.07 wt.% P was solution annealed and cold deformed to true strains ranging from 0.1 to 0.9. After being aged at 510°C for different times, the deformed alloy was characterized using the measurement of Vickers hardness, optical microscopy and transmission electron microscopy. During the isothermal aging, the hardness of the deformed alloy showed three distinct stages as a function of aging time; this hardness behavior was associated with the interactions between precipitation, recovery and recrystallization. The amount of prior deformation and aging time influenced the interactions of the three processes. On aging, the lightly deformed alloy exhibited a retarded recrystallization process and therefore an efficient hardening response. The heavily deformed alloy (>0.7 strain) showed an accelerated process of recrystallization so that a long time aging (e.g. 60 min) resulted in an inefficient precipitation hardening due to the increased softening with the progress of recrystallization. The results of this study suggest that the precipitation process should occur before the onset of recrystallization during the aging of a deformed supersaturated alloy in order to result in an efficient hardening. This condition can be achieved by controlling the amount of prior deformation, aging temperature and time.

Elimination of Intergranular Corrosion Susceptibility of Cold-Worked and Sensitized AISI 316 SS by Laser Surface Melting

Susceptibility to intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) due to sensitization is one of the major problems associated with austenitic stainless steels. Thermal exposures encountered during fabrication (welding, hot working, etc.) and elevated temperature service may lead to sensitization of components of austenitic stainless steels. Laser surface melting (LSM) is an in-situ method to increase the life of a sensitized component by modifying the surface microstructure without affecting the bulk properties. In this paper, the results obtained in the attempt to improve IGC resistance of coldworked and sensitized 316 SS by LSM are presented. Type 316 SS specimens cold worked to various degrees ranging from 5 to 25% reduction in thickness and sensitized to different degrees by exposing at 898 K for different durations were laser surface melted using continuous wave (cw) CO2 laser. ASTM standard A262 practice A, optical metallography, and ASTM standard G108 were used to characterize the specimens before and after LSM. Influence of prior deformation on the desensitization behavior was evaluated for the laser melting conditions adopted during the investigation. Complete dissolution of M23C6 due to laser melting and suppression of re-precipitation due to rapid quenching result in a desensitized homogenous microstructure, which is immune to IGC. Under identical laser melting conditions, the extent of desensitization decreases with an increase in the degree of cold work, and hence, higher power levels and an extended interaction time must be adopted to homogenize the sensitized microstructure with prior cold work.

Effect of prior deformation on A s temperature of martensite in Fe-Ni alloys

The influence of prior deformation on reverse martensitic transformation temperature in Fe-high Ni alloys has been investigated by several workers. For example, Pope has studied the reverse transformation temperature of an Fe-30%Ni alloy with respect to deformation, and found that the start temperature of reverse transformation (A{sub s}) increased continuously with increasing deformation. Mel'nikov et al. have examined the variation in A{sub s} with deformation temperature in an Fe-30%Ni alloy, and reported that the deformation at ambient temperature shifted the A{sub s} to higher temperature, while deformation applied between 60 and 100 C lowered the A{sub s}. The above investigation dealt only with the A{sub s} of lenticular martensite having partially twinned substructure, but few studies have been made on lath martensite with highly dislocated substructure of an Fe-Ni alloy. In the present study, lath martensite of an Fe-15%Ni and lenticular martensite of an Fe-31%Ni alloy were prepared, and the variation in A{sub s} with prior deformation at room temperature was investigated and compared with each other.

Influence of prior deformation on the sensitization of AISI Type 316LN stainless steel

The sensitization behaviour of a nuclear grade AISI 316LN stainless steel (SS) was studied for various cold-work levels ranging from 0% (mill-annealed) to 25% reduction in thickness. ASTM standard A262 Practices A and E were adopted to detect the susceptibility to intergranular corrosion. The results obtained in these tests were used to construct time-temperature-sensitization (TTS) diagrams. Using these data, the critical linear cooling rate was calculated, above which there is no risk of sensitization. In order to predict the sensitization behaviour during practical cooling conditions, Continuous-cooling-sensitization (CCS) diagrams were established utilising the TTS diagrams by a mathematical method. The influences of prior deformation and nitrogen in the alloy on the sensitization kinetics are discussed. It was found that nitrogen addition retards the sensitization kinetics and that t min (minimum time required for sensitization at nose temperature) increases by two orders of magnitude in Type 316LN SS compared to that of Type 316 SS at the different prior deformation levels. Cold-working up to 15% accelerates the onset of carbide precipitation and on further cold working there is not much difference in the kinetics. Desensitization is faster in highly cold-worked material, especially at high temperatures.

The influence of prior deformation on hydride precipitation in zircaloy

Precipitation of hydrides has been studied in samples of Zircaloy subjected to prior tensile or compressive deformation before charging with hydrogen. The mean residual stress pattern in the alloys prior to charging was assessed by neutron diffraction techniques and provided a rough guide as to the preferred site of hydride nucleation. Heterogenous hydride nucleation at grain boudaries or twin boundaries was commonly found in samples subjected to 4% prior deformation, while transgranular hydrides were most frequently observed after a prior 1/2% compressive deformation or an annealing. The local stress state at grain boundary facets or twins is thought to be the deciding factor in determining where hydrides nucleate and how hydride stacks form.

Influence of Prior Deformation on The Sensitisation of AISI Type 304 Stainless Steel and Applicability of EPR Technique

The influence of prior plastic deformation on the degree of sensitisation (DOS) of AISI 304 stainless steel has been studied for various levels of cold work ranging from 0 to 25% using the ASTM standard A262 practices A and E, and the electrochemical potentiokinetic reactivation (EPR) technique. Peak current density and reactivation charge density were determined from single loop EPR experiments and the ratio of the peak current during reactivation to that during activation was determined from double loop EPR experiments. The feasibility of using these techniques for determining the DOS in cold worked samples was examined. The reproducibility of the EPR results is rather poor. There appears to be no well defined systematic trend between the degree of cold work and the DOS as estimated from the EPR parameters. EPR parameters were found to be dependent on the temperature of aging and the degree of prior cold work. Threshold values above which a sample can be treated as sensitised cannot therefore be determined from EPR tests without being confirmed independently by conventional ASTM standard methods.

Influence of prior deformation on precipitation of Cu-1.9 wt% Be-0.1 wt% Mg alloy

Influence of prior deformation on precipitation of Cu-1.9 wt% Be-0.1 wt% Mg alloy

Effect of prior deformation on Co-Ti, Co-Ti-Nb and Co-Ti-Fe alloys

The influence of prior deformation in spinodally decomposing Co-Ti, Co-Ti-Nb and Co-Ti-Fe alloys has been investigated using transmission electron microscopy and hardness isotherms. Deformation seems to have an influence on the decomposition sequence in Co-3% Ti alloy; however, it does not affect the sequence of transformations in the ternary alloys. The ternary alloys show peak hardness after deformation and subsequent annealing at 873 K. The peak hardness of the deformed alloys occurred quite early, compared with the undeformed alloys.

Influence of Prior Deformation and Composition on Continuous Cooling Sensitization of AISI 304 Stainless Steel

Abstract This paper addresses the question of the combined effect of carbon content and prior cold work on the sensitization of AISI 304 stainless steel (SS). It was found that prior.cold work increased the critical cooling rate required to produce sensitization (i.e., made it easier) for steels containing from 0.017 to 0.077 wt% C. Both A262 practice A and practice E tests were used. The A262A test revealed sensitization at higher cooling rates than the A262E test (for all heats studied). The influence of peak temperature was also studied. Sensitization was found to be most rapid when the peak temperature was in the 700 to 800 C range, with the exact temperature depending upon the carbon content.

Yielding anisotropy from the bauschinger effect and crystallographic texture in drawn HSLA steel sheet

The influence of prior deformation by in-plane compression, a laboratory technique used to simulate drawing in sheets, on the yield-strength anisotropy of an 80-ksi minimum yield-strength vanadium-nitrogen HSLA steel has been documented and the origin of this anisotropy has been investigated. A large tensile yield-strength anisotropy (40 to 50 ksi difference between orthogonal directions in the plane of the sheet) was observed for all prior effective strains investigated (from ee ≃ 0.1 to ee ≃ 0.5). Based on: (1) an analysis of Tresca-type yield loci obtained before and after in-plane compression, and (2) yield-strength anisotropy calculations performed with a Taylor model and a Sachs model using results of crystallographic texture measurements, it was concluded that the tensile yield-strength anisotropy originates primarily from the Bauschinger effect. The anisotropy due to texture is much smaller (15 pct of the total yield strength difference) and of opposite sign.

The Influence of Prior Deformation on Continuous Cooling Sensitization of Type 304 Stainless Steel

Abstract Continuous cooling sensitization (CCS) of Type 304 stainless steel results from cooling through the sensitization temperature range, rather than isothermally heat treating at a specific temperature. In a previous study,1 CCS was performed on specimens which were annealed prior to the CCS thermal cycle. This present study is concerned with CCS on specimens which were deformed prior to the CCS test. Prior deformation alters both the isothermal sensitization behavior and the CCS. This paper compares the two and constrasts the behavior of deformed specimens with specimens which have been annealed. Deformation increases the cooling rate at which sensitization can occur, providing the peak temperature is 900 C or lower. If the peak temperature is 1000 C or higher, recrystallization removes the worked structure, and the material sensitizes at the same rate as annealed material.

The influence of prior deformation on the yield stress of a metastable Fe-Ni-C austenite

The influence of prior deformation on the yield stress of a metastable Fe-Ni-C austenite

Continued tensile creep studies on extruded chromium alloys

The high-temperature properties of a variety of chromium alloys, ranging from binary to quinternary systems, have been assessed by tensile creep tests in air at 1038° and 1065°C. The influence of prior deformation and chromium purity on creep properties, and the relationship between structure and creep strength, are considered.

The tensile creep properties of some extruded chromium alloys

The high temperature properties of a variety of extruded chromium alloys, ranging from binary to quinternary systems, have been assessed by tensile creep tests in air at 1038°, 1050° and 1065°C. A ternary alloy consisting of 2% tantalum and 0.05% boron has given the best result, with a rupture life in excess of 100 h at 1065°C under a load of 20,000 lb./in. 2 Attention is directed both to the role of precipitation and the influence of prior deformation on creep properties.