Increase In Degree Of Deformation Research Articles

Macromolecular and pore structures of Chinese tectonically deformed coal studied by atomic force microscopy

In this study, the macromolecular and nanoscale pores of different types of tectonically deformed coals were characterized by AFM. The nanostructures of coal differed in terms of the metamorphism degree, deformation degree, and deformation properties. The macromolecular grid-like structure of low-rank bituminous coal was loosely reticular, and the round or elliptical pores between chains were largely isolated. The macromolecular reticular grid-like structure of high-rank bituminous coal was more compact than that of low-rank bituminous coal. The large molecules of anthracite exhibited enhanced polymerization with significant reductions in the spacing between macromolecular layers. The reticular grid-like structure of this coal was fairly compact, and the pores between the chains were squeezed flat. Flat micropores were the predominant pore morphology in this type of coal. Metamorphism generally increased the quantity of micropores in the coal. The macromolecular reticular grid-like structures and pore structures of coal varied according to their properties and deformation degree. Under brittle deformation, the ratio of the transitional pores and the interconnectivity of the pores increased with increasing deformation degree. This phenomenon was beneficial for gas diffusion. Under ductile deformation, the coal surface exhibited creep flow features, the surface pore morphology of the coal was irregularly developed, and the ratios of micropores and transitional pores in the coal increased.

A research on the creep properties of titanium matrix composites rolled with different deformation degrees

(TiB+La2O3)/Ti composites were in situ synthesized and deformed with different deformation degrees. The influence of TiB whisker orientation and grain refinement on the creep properties of titanium matrix composites (TMCs) are discussed. The creep test reveals that the steady state creep rate of TMCs first decreases and then increases with the increase of deformation degree, which can be attributed to competing effects: TiB whisker rotating to the rolling direction, α plate grain boundary hindering and pinning dislocations can all decrease the creep rate, however, dislocation movement on the α plate grain boundary and dislocation emitting from the α plate grain boundary can both increase the creep rate.

Influence of Rotary Forging Process on Microstructure and Properties of Niobium-Titanium Alloy

High conductive Niobium-Titanium alloy has the advantages of good corrosion resistance, high specific strength, good thermal stability, etc. The rotary forging technology of Nb-Ti alloy ingot with type prepared by vacuum smelting method was studied. The results show that coarse and homogeneous casting-microstructure becomes strip deformation microstructure after rotary forging. With the increase of deformation degree and deformation velocity, the space of strip deformation microstructure decreases and yield strength of alloy increases. Nb-Ti alloy bar after deformation is still type alloy with a thermal stability.

Research on Microstructure and Properties of Pure Copper Tube during Rolling Process

The pure copper tube with strong axial orientation columnar grain and equiaxed grain respectively were rolled using a three-roller precision tube mill. Optical microscope, hardness testing machine and universal testing machine were used to investigate the microstructure and mechanical properties of the pure copper tube rolled with different deformation degrees. The results show that the pure copper tube with two kinds of microstructure can be directly rolled from the dimension of Φ68.5mm×57.9mm to Φ34.7×30.4mm by 8 passes with accumulated deformation degree nearly 80% and without intermediate annealing. With the increasing deformation degree, the primary columnar grain boundaries of the pure copper tube with columnar grain blurred gradually until completely disappeared. However, the microstructures of pure copper tube with equiaxed grain completely transformed into fibrous microstructures when the deformation degree reaches to 79.11%. The columnar grain is without transverse grain boundaries but with small-angle boundary, which is conducive to axial deformation. It is also found that with the increasing deformation degree, the tensile strength of pure copper tube increased steadily, while the elongation decreased gradually. The elongation of pure copper tube with columnar grains is higher and the microhardness is lower than that of equiaxed grains, indicating that the cold deformation properties of pure copper tube with columnar grain was more excellent.

Effect of thermo-mechanical treatment on properties improvement and microstructure changes in copper–gold alloy

This paper reports on the changes in hardness, microhardness, electrical conductivity and microstructure using the optical and scanning electron microscopy of the copper-based alloy with 4.5at.% gold, during the complex thermo-mechanical treatment, which is used to create the conditions for development of anneal hardening effect. It was shown that the increase of deformation degree during both the prefinal and final rolling resulted in the increase of hardness, microhardness and electrical conductivity values, due to changes in the microstructure caused by the cold plastic deformation. The differences in the initial microstructure of the homogenized and quenched samples created the different deformation strengthening rates. Low-temperature annealing of the finally rolled samples contributed to a further increase of the above properties due to the anneal hardening effect. The improvement of the properties during the annealing was accomplished in two stages, and the best combination of properties was achieved in the second stage of hardening after annealing at 260°C. Minor changes in the microstructure were noticeable during the annealing at 260°C, but the EDS analysis showed a significant change in the concentration of gold atoms within the grain.

Microstructural Evolutions of a High Temperature Titanium Alloy Processed by Thermal Mechanical Treatments

TG6 alloy is a new titanium alloy which has been designed to reach the service temperature of 600°C. The microstructural evolutions of TG6 alloy under different thermal mechanical treatments were studied. It was found that lamellar microstructures with basketweave α lamella are obtained for TG6 alloy forged in β field. The evolution mechanism is transformed from dynamic recrystallization to dynamic recovery and the thickness of α lamella increases with increasing forging temperature. The aspect ratio of α lamella decreases firstly and then increases with increasing deformation degree. Grain boundary α lath appears when the deformation degree is less than 40%. The thermal mechanical treatments, including deformation in β field firstly and then deformation in α+β field result in the transformations of the microstructures drastically. The deformation degree in α+β field decides the final microstructure. The deformation degree of 20% in α+β field results in partial globular α phase.

Amorphization of Titanium Nickelide by means of Shear under Pressure and Crystallization at the Subsequent Heating

Transmission electron microscopy and X-ray diffraction were used to study structural changes in the Ti-50.5 at. % Ni alloy upon severe plastic deformation by shear under pressure and subsequent heating. An increase in the degree of deformation leads sequentially to a martensite transformation, twinning of martensite crystals, formation of reorientation bands, development of rotational modes of deformation, formation of a nanocrystalline structure, and finally amorphization. A scheme of the formation of amorphous structure of the alloy during deformation is suggested based on the observed structural changes. It has been found that a reverse martensitic transformation might be one of mechanisms of plastic deformation of the alloy. Therefore, as the degree of deformation increases, first forward and subsequently reverse martensitic transformations can occur. The formation of an amorphous structure starts as the degree of deformation reaches 4.2 (one revolution of Bridgman anvils); at a degree of deformation of 6.8 (5 revolutions of the anvils), the process is virtually completed. The crystallization of the amorphous alloy upon heating starts even at 200°C. However, upon heating up to 300°C (for 0.5-h holdings), the kinetics of crystallization is slow. After annealing at 350°C, the complete crystallization with the formation of a nanocrystalline structure with a grain size of 20-70 nm takes place

Effect of Coil Parameters on Rivet Deformation in Low Voltage Electromagnetic Riveting

Electromagnetic riveting is a kind of energy conversion technology and forming coil is the key component of energy conversion. Coil parameters include the turns and wire cross section size. The effects of coil parameters on discharge current, riveting force, rivet deformation degree and energy conversion rate were investigated by experimental method in low voltage electromagnetic riveting. The results show that with the coil turns increasing, coil inductance increases, discharge current amplitude decreases, cycle increases, rivet deformation degree increases and the energy conversion rate improves when the coil wire cross section size is the same. And with the coil wire width increasing, the coil resistance decreases, discharge current amplitude increases, rivet deformation degree increases and the energy conversion rate improves when the coil turns is same. By rational design of coil turns and wire section size, low voltage electromagnetic riveting is an effective way to realize deformation of strain rate sensitive material TA1 rivets.

고 Mn 오스테나이트계 스테인리스강의 기계적성질에 미치는 가공유기 마르텐사이트 변태의 영향

The effect of deformation induced martensite transformation on the mechanical properties in austenitic stainless steel with high Mn was studied. `-martensite was formed by deformation in austenitic stainless steel with high Mn. Deformation induced `-martensite was formed with surface relief by cold rolling. With the increase of deformation degree, volume fraction of deformation induced martensite was increased rapidly in early stage of deformation and then, increased slowly. With the increase of deformation degree, hardness and tensile strength were rapidly increased with linear relations, while elongation was rapidly decreased and then slowly decreased. Hardness, tensile strengths and elongation were influenced strongly by deformation induced martensite.

Gradual softening of Al–Zn alloys during high-pressure torsion

Evolution of the microstructure and mechanical properties of Al–30wt.% Zn alloy after the severe plastic deformation (SPD) by the high-pressure torsion has been investigated in detail in dependence on the increasing deformation degree. SPD leads to the gradual grain refinement and decomposition of the Al-based supersaturated solid solution. Measurements of the microhardness reveal a successive softening of the alloy with the increased deformation degree.

Free volume evolution of pre-annealed Zr55Al10Ni5Cu30 bulk metallic glass during rolling

Traces of nanocrystals are introduced into Zr55Al10Ni5Cu30 bulk metallic glass through isothermally annealing the glass at 715 K for 30 min. The pre-annealed samples are rolled at different strain rates up to 95% thickness reduction at room temperature. The thermal stability and the free volume of the deformed sample are examined by differential scanning calorimetry. It is found that the thermal stability does not change with deformation degree. At any strain rate, free volume content increases continuously with the increase of deformation degree without saturation. As strain rate increases, however, the free volume content with the same deformation degree first increases and then decreases, which is significantly different from the case of the metallic glass with monolithic amorphous structure under plastic deformation.

High temperature deformation of Ti alloy superplastically embedded with HA

This study is focused on the feasibility of forming titanium (Ti) alloy superplastically embedded with hydroxyapatite (HA) nanolayer. The superplastically embedded sample having a layer thickness of approximately 249 nm and a surface hardness of 661 HV is deformed under compression mode at 1200 K for 10, 20 and 30% deformation degree. The HA layer thickness decreases to approximately 241, 223 and 206 nm with increasing deformation degree. Surface morphology reveals microcracks and delaminations of HA at certain areas as deformation degree is increased. Comparison using non-superplastic embedment sample shows that a significant degree of surface deterioration occurs even at 10% deformation. Based from the results, it can be concluded that the superplastically embedded HA layer is still strongly intact to the substrate surface even after deformation process without deteriorating the HA structure.

Rolling-induced microstructure change in Zr65Al7.5Ni10Cu12.5Ag5 bulk metallic glass

The microstructures and free-volume evolutions of as-cast and pre-annealed Zr65Al7.5Ni10Cu12.5Ag5 bulk metallic glasses during rolling deformation have been investigated. No phase transformation is detected in the as-cast/rolled specimen. However, the structural stability of the glass against plastic deformation is worse after pre-annealing, indicated by nanocrystallization in pre-annealed/rolled specimens with large deformation degrees. Moreover, with increasing deformation degree, the free-volume content in a pre-annealed/rolled specimen increases at a lower average rate than that in an as-cast/rolled specimen.

Effects of stretching processing parameters on the mean elongation ratio and maximum spread ratio of heavy forgings

Heavy forgings are the essential parts of some nuclear, electrical power generation, rolling mill equipments. The rigid-viscoplastic finite element models (FEM) were established to study the effects of processing parameters (deformation degree, tool width ratio, blank width ratio, strain rate, friction, and forming temperature) on the mean elongation ratio and maximum spread ratio of heavy forgings during stretching process. A new formula (LD model) is proposed to predict the mean elongation ratio for stretched heavy forgings. The predicting capabilities of LD model were verified by experiments. Results show that: (1) The mean elongation ratio and maximum spread ratio increase with the increase of deformation degree; (2) When the tool width ratio is decreased, the mean elongation ratio increases and the maximum spread ratio decreases; (3) When the blank width ratio is increased, the mean elongation ratio increase and the maximum spread ratio decrease; (4) The mean elongation ratio is not affected by strain rate, friction, and forming temperature. However, the effects of these three process parameters on the maximum spread ratio of deformed block are significant; (5) There is a good agreement between the experimental results and predictions by LD model, which confirms that the proposed LD model is valid for the practical industrial productions.

Effect of Deformation Degree on Mechanical Properties of AZ80 Magnesium Alloy

The mechanical properties and microstructures were investigated for AZ80 Mg alloy during plane strain compression and extrusion processing. The results show the tensile strength increases with the increasing deformation degree in the two-phase zone due to sufficient dynamic recrystallization and work-hardening effect. In single-phase zone, the tensile strength increases firstly and then does not varies basically when the deformation degree is greater than a certain critical value. This is very beneficial to optimize processing parameters to obtain microstructure with improved mechanical behavior.

Numerical Simulation of Vertical Extrusion Process of Large-Sized Seamless Steel Tube with Thick Wall

The software of finite element simulation DEFORM-3D was used to simulate the extrusion process of the large diameter thick wall seamless steel tube, and the effective stress and load curves were analyzed in the situation of different concave die mould cone Angles. The simulation results show that with the increase of deformation degree, the effective stress and load of the blank increased gradually first and then reached a plateau. With the increase of the concave die mould cone Angle, the load of top die decreased.

The Thickness Distribution of Oxidation Film on Tapered Pipe Surface in Dieless Drawing

The thickness distribution of oxidation film on the surface of AISI304 stainless steel tapered pipe, its influence factors, and the effect of metal matrix deformation on oxidation behavior during dieless drawing were studied in this paper. The results showed that oxidation rate was affected strongly by induction heating temperature and deformation degree. The thickness distribution of oxidation film was uneven and increased from the larger diameter end to the smaller diameter end along the axial direction of tapered pipe. When induction heating temperature raised or the distance between heat and cold sources was increased, or feed speed was decreased, oxidation rate was accelerated and oxidation film on the tapered pipe surface thickened significantly, due to massive cracks in oxidation film induced by deformation of metal matrix. The density and width of cracks in oxidation film were enlarged, and the thickness of oxidation film increased with the increase in deformation degree.

Influence of Degree of Cold-Drawing on the Mechanical Properties of Low Carbon Steel

Low carbon steel metal is used for the manufacture of nails. Steel wire with <0.3% C content is cold-drawn through a series of drawing dies to reduce the diameter of the wire to the required diameter of the nails. A 0.12%w C steel wire cold drawn progressively by 20%, 25%, 40% and 50% was investigated. The influence of the degree of cold drawing on the mechanical properties of the carbon steel material were studied using the tensile test, impact test and hardness test experiments in order to replicate the service condition of the nails. The tensile test was done on a Montanso® tensometer to investigate the yield strength and the tensile strength of the material as the degree of deformation increases. An Izod test was used to determine the impact toughness of the steel using the Hounsfield impact machine and the hardness numbers were obtained for the different degrees of drawn deformation of the steel on the Brinnel tester. The study used the stress-strain relationship of the tensile test experiment to study the effect of the degree of cold-drawing deformation on the yield strength and tensile strength properties of the low carbon steel. The yield strength of the material was observed to reduce with increasing degree of cold-drawing, an indication of reduction in the ductility and the tensile strength of the material reduced with increasing degree of cold-drawn deformation. The ability of the material to resist impact loads when nails are hammered reduced with increasing degree of drawn deformation as a result of strain hardening of the material after the drawing operation. However the resilience of the material to further cold drawn deformation increased with increasing degree of deformation as evident in the Brinnel hardness number which increases with the degree of drawing deformation. This is an indication of the material’s approach to brittleness as the degree of drawn deformation increases.

Changes in the grain structure of metallic materials upon plastic treatment

Experimental data on structural changes in the process of plastic deformation of polycrystalline copper and stainless steel have been reviewed. It has been shown that the mechanisms of the formation of a new grain structure, i.e., dynamic recrystallization, depend on the conditions of treatment or flow stresses at the steady-state stage, which are determined unambiguously by the temperature and strain rate. Upon hot deformation (low flow stresses), it is local migration (bulging) of grain boundaries and subsequent growth of these bulgings that seem to be the main mechanism of formation of new grains. Since the nucleation of new grains in this case is of a heterogeneous character, the microstructure evolution can be classified as a discontinuous dynamic recrystallization. Upon worm or cold deformation (high flow stresses), we deal with a dynamically recrystallized structure only after very high degrees of deformation. The new grain structure is formed due to the growth of angular misorientation between subgrains with an increase in the total degree of deformation, which can be considered as a continuous dynamic recrystallization. Changes in the mechanisms of dynamic recrystallization with changes in the conditions of treatment lead to a bimodal dependence of the size of dynamically recrystallized grains on the flow stresses.

Free-volume evolution of glassy Zr65Al7.5Ni10Cu17.5 during inhomogeneous deformation

Free-volume evolutions of the as-cast and pre-annealed Zr65Al7.5Ni10Cu17.5 metallic glasses during cold-rolling were investigated using differential scanning calorimetry. As deformation degree increases, free volume in the glasses always increases first and then saturates above a critical strain, while the structure remains completely amorphous. The glass with less initial free volume possesses a higher increase rate of free-volume content during deformation, and as a result the free-volume contents of all the glasses approach each other at higher strains. Coalescence of free volume in shear bands into nanovoids is proposed to be responsible for the saturation of free-volume content at high strains.