Effect Of Prior Plastic Deformation Research Articles

Effect of Prior Plastic Deformation on the α-Cr Precipitation in a Binary Ni-Cr Alloy

The effect of prior plastic deformation on the discontinuous precipitation in a supersaturated binary Ni-Cr alloy (42 wt pct Cr) was investigated. Solutionised samples were cold rolled to different extents of reduction (20, 50 and 70 pct) and then subjected to aging heat treatments in the temperature range of 923 K to 1123 K (650 °C to 850 °C) for different time periods, resulting in the precipitation of α-Cr in various morphologies. The α-Cr precipitates were in the form of lamellar discontinuous precipitation, acicular continuous precipitation along the deformation bands, globularization and equiaxed precipitation concurrently with matrix recrystallization. The volume fraction of each morphology varied according to the heat treatments. Overall, the prior plastic deformation had a retarding effect on the kinetics of discontinuous precipitation and accelerated the kinetics of continuous precipitation. The retardation of discontinuous precipitation was attributed to the loss of supersaturation of the matrix due to the other competing modes of precipitation supported by deformation. Plastic deformation prior to aging is shown to be a possible route for engineering the microstructure in this alloy.

Effect of prior plastic deformation and deformation rate on the corrosion resistance of AISI 321 austenitic stainless steel

In this work, the role of prior plastic deformation and rate of deformation on the corrosion behavior of plastically-deformed metastable AISI 321 austenitic stainless steel in 3.5 wt% NaCl solution was investigated. Samples were deformed under dynamic (έT = 8.8 × 103 s−1) and quasi-static (έT = 4.4 × 10−3 s−1) loading conditions to a common true strain of ~0.86 using a split Hopkinson pressure bar and Instron R5500 mechanical testing systems, respectively. While the specimen subjected to quasi-static compression experienced substantial deformation-induced martensitic transformation, phase transformation was significantly suppressed in the specimen subjected to dynamic loading due to temperature rise during impact. The yield strength of the specimen under dynamic impact loading is higher than that of the specimen compressed under quasi-static loading condition. However, the specimen deformed under quasi-static loading shows higher strain-hardening rate compared to the specimen subjected to dynamic impact load which is dominated by thermal softening at true strain beyond ~0.6. Using the Tafel polarization and impedance spectroscopic techniques, the deformed specimens were found to be more resistant to chloride-induced intergranular corrosion at room temperature compared to the undeformed ones. The specimen subjected to quasi-static loading exhibits significantly higher corrosion resistance in comparison with those subjected to dynamic loading. This could be attributed to the formation of a denser passive film on the specimen subjected to quasi-static loading on exposure to the test electrolyte over time. In addition to the role of particles on pitting formation in metals exposed to corrosive environment, the current work affirms the important role of prior plastic deformation on the corrosion behavior of the investigated alloy. Evolution of twins and stable-end orientation (preferred crystallographic orientation) in both parent (austenite) and product (martensite) phases nullified what would have been the negative effects of plastic deformation (due to the associated deformation-induced martensitic phase and stored defects) on the corrosion resistance of the investigated stainless steel.

Effect of ausforming on the anisotropy of low temperature bainitic transformation

Ausforming is the process by which austenite is plastically deformed prior to bainitic or martensitic transformation. The advantages of such a process on the kinetics of the bainitic transformations have already been reported, but little is found about the effect on the morphology and crystallography of the final microstructure, and in most cases the studies deal with high C steels. Since ausforming has been suggested to be an alternative to transfer the concept of nanostructured bainite to medium carbon contents, the necessity to study the effect of prior plastic deformation on the subsequent bainitic transformation in those steels arises. By means of techniques such as high-resolution dilatometry, scanning electron microscopy, electron backscatter diffraction and X-Ray diffraction, it has been proven that, in a medium carbon steel (0.4 wt%), the macroscopic isotropy that characterizes the bainitic transformation can be altered, under certain conditions, by plastically deforming austenite prior to transformation. The alteration is such that, at low temperatures, the interpretation of the dilatometric response or the plate thickness measurements can be hindered. In addition, the final microstructure is also affected, presenting highly ordered bainitic ferrite plates, most of them correspondent to specific crystallographic variants.

Influence of plastic deformation on the precipitation sequence in an AA6061 alloy

The purpose of this work is to study the effect of prior plastic deformation on the precipitation mechanisms of MgxSiy in an AA6061 alloy. Differential scanning calorimetry (DSC), tensile testing and transmission electron microscopy (TEM) were used to characterize the precipitation sequence in samples that were isothermally aged at 180 °C with and without prior plastic deformation. Compressively deforming the AA6061 alloy by 4% caused a shift in the exothermal precipitation peaks to lower temperatures (DSC) and enabled the peak strength condition to be reached after a shorter aging period, revealing that plastic deformation accelerated the precipitation kinetics. TEM analysis determined that the accelerated precipitation kinetics in the deformed material was due to heterogeneous precipitation of the Q′ phase along dislocation lines and a modification of the precipitation sequence with the L, C and Q′ phases dominating over the β′′ phase (which is dominated in the non-deformed material). Additionally, the formation of β′ was largely suppressed by plastic deformation.

The effect of deformation on γ-ε martensitic transformation in an Fe-Mn-Mo alloy

Effect of prior plastic deformation of austenite on the martensite start temperature, volume fraction and strength of martensite have been studied in an Fe-14.3%Mn-3.7%Mo alloy. Mo was chosen to examine the possible effect of the third alloying element in an Fe-Mn based alloy and the obtained results were compared with those of the Fe-Mn binary alloys given in the literature. Predeformation of austenite created considerable changes on the formation characteristics and also the strength of the martensitic phase and the obtained results were discussed in terms of the dislocations formed during the deformation process.

Effect of prior plastic deformation and creep strain on fatigue damage for a high-temperature alloy

A procedure is developed, an experimental study is provided, and a comparative evaluation is given for the effect of prior plastic deformation and creep strain on fatigue damage for high-temperature metallic materials on the example of alloy eI827. A different effect is demonstrated for prior plastic deformation and creep strain on fatigue damage of this alloy at 1073 K. In the case of prior creep a marked difference is established from the hypothesis of linear summation for damage in the direction of weakening during evaluation of the overall fatigue and static damage both in the form of relative endurance and relative strain.

The mechanical properties of the matrix in continouos-fibre 6061 aluminum-alloy metal-matrix composites

Various factors affecting the matrix properties of metal-matrix composites have been investigated by a series of experiments on the unreinforced matrix material. The effect of the rate of cooling from the fabrication temperature to room temperature is studied by comparing the stress-strain behaviour of quenched and air-cooled specimens. During cooling, fibres constrain the contraction of the matrix owing to the difference in thermal-expansion coefficients of the two materials. The effect of this constrains was simulated by clamping aluminum specimens to a steel plate during heat treatment. It was found that the main effect of the constraint was to produce strain-hardening and a much sharper yield point. The strain-hardened stress-strain curve can be predicted in terms of the material's room-temperature stress-strain curve if the temperature change and the coefficients of thermal expansion of the fibre and matrix are known. Subsequent ageing of the matrix was also examined. The presence of rseidual stress does not affect the amount of age-hardening. However, the effect of prior plastic deformation reduces the amount of precipitation-hardening. Creep of the matrix during cooling appears to be negligible, but some relaxation of residual stress in the matrix material may subsequently occur at room temperature.

Effect of temperature and deformation on the destruction of bimetal steel 80-steel 12Kh18N10T

Many structural composite materials operate under elevated temperature conditions. The properties of these materials at temperatures exceeding 600 o C have been previously studied although there is practically no information in the literature about their operation at 200-500 o C. In view of this a study was made in the present work of a composite material (bimetal) which is a cylindrical core of carbon steel 80 clad with steel 12Kh18N10T. The study of the bimetal and its components was performed at 200-500 o C. The effect of prior plastic deformation at these temperatures on bimetal properties was studied simultaneously

Effect of prior plastic deformation on the low-cycle fatigue of 03Kh13AG19 chrome-manganese steel at a temperature of 4.2�K

Effect of prior plastic deformation on the low-cycle fatigue of 03Kh13AG19 chrome-manganese steel at a temperature of 4.2�K

Eu precipitation in plastically deformed alkali halides

The effect of prior plastic deformation on the precipitation kinetics of europium-doped NaCl, KCl and KBr has been analysed using optical absorption, photoluminescence and electron paramagnetic resonance techniques. In the host NaCl, plastic deformation produces a considerable influence on the Eu precipitation processes into the metastable and stable phases. The introduction of defects by mechanical treatment strongly favours the formation of a second phase precipitate which does not nucleate in the undeformed samples and which can be tentatively identified as either NaEuCl3 or Na2EuCl4. In contrast, in the hosts KCl and KBr, plastic deformation does not influence Eu precipitation into the metastable phase which nucleates at low temperatures (<100 degrees C) and was previously related with the Suzuki phase, indicating that the nucleation of this phase is homogeneous. However, the rate of Eu precipitation into metastable and stable phases with EuX2 structure (X=Cl, Br) which nucleate at high temperatures ( approximately 200 degrees C) is enhanced in the plastically deformed samples, suggesting that the nucleation of these phases is heterogeneous. The effect of dislocation on pre-existing Eu second phase precipitates in both KCl and KBr has also been investigated. The results suggest that moving dislocations cause the re-solution of the preexisting Suzuki precipitates, creating complexes of a much simpler nature, while they create plate-like zones when acting on pre-existing stable dihalide EuX2 second phase precipitates.

The influence of thermal and mechanical histories on case II sorption of methanol by PMMA

Previously published data [6] relating kinetics of the Case II penetration of methanol into PMMA to the thermal history of the samples are discussed in relation to the detailed predictions of a model of the sorption process [4]. It is clear that fast cooling through T g enhances sorption rates through the influence of the thermal history on the rate of mechanical response of the polymer glass. Detailed measurements are reported of the effect of prior plastic deformation of the polymer glass on the Case II kinetics. The results indicate that the sorption rate is enhanced as a consequence of the yielding process itself, irrespective of whether the hydrostatic component of the stress is compressive or tensile. In addition to this “yield factor”, there is another factor which becomes significant at high strains. It is related to the sign of the plastic strain in the glass in the direction normal to the penetrant front. Prior extension normal to the front is found to reduce the penetration rate as a function of strain, and compression to further enhance it. The effect is described as the “retraction factor”.

Effect of prior plastic deformation of high-strength steel on the form of the critical-state curves

Effect of prior plastic deformation of high-strength steel on the form of the critical-state curves

Effect of plastic deformation on the physicomechanical properties of tungsten carbide-cobalt hard alloys

A study was made of the effect of prior plastic deformation on the hardness, strength, coercive force, and electrical resistivity of tungsten carbide-cobalt hard alloys containing 10–25% cobalt. Plastic deformation decreases the hardness of the alloys. Up to a deformation of about 5–6%, all the alloys investigated showed a marked drop in hardness. Further deformation did not decrease the hardness of alloy VK25; for the alloys with lower cobalt contents, the hardness decrease was less pronounced.