Pure Metal Type Research Articles

Influence of P Content on Microstructure and Texture Evolution of the Oxygen-Free Copper

The present work aims to systematically investigate the influence of P content on the microstructure and texture evolution of oxygen-free copper during intermediate annealing and final cold rolling. The microstructure and texture evolution were studied by electron backscattered diffraction and transmission electron microscopy. With the addition of P, the grains refined and a large fraction of low angle grain boundaries (LAGBs) emerged after intermediate annealing. The texture transformed from pure metal type for pure Cu to the α-fiber texture which included brass and Goss texture as P was added. The recrystallization temperature increased with the addition of P, and refined grains after the final cold rolling process. The addition of elemental P would reduce the stacking fault energy, and then influence the transformation of the deformation and recrystallization texture of the copper. Accompanied by the evolution of the deformation texture, the recrystallization cubic texture {001}<100> was suppressed and a strong {236}<385> brass recrystallization texture emerged with the addition of elemental P after the intermediate annealing and subsequent final cold rolling process.

Microstructure and texture of heavily cold-rolled and annealed fcc equiatomic medium to high entropy alloys

The evolution of microstructure and texture after heavy cold-rolling and annealing was investigated in FCC equiatomic medium to high entropy alloys. For this purpose medium entropy ternary CoFeNi and quaternary CoCrFeNi, and high entropy quinary CoCrFeMnNi alloys were cold-rolled to 90% reduction in thickness and annealed at different temperatures. The ternary alloy showed the development of lamellar microstructure and pure metal type texture after heavy cold-rolling. In contrast, the quaternary and quinary alloys showed heavily fragmented microstructure and brass dominated texture. After annealing, the ternary alloy showed abnormal grain growth at lower annealing temperatures and strengthening of the cube component ({001}<100>) with increasing annealing temperature. In contrast, the quinary and quaternary alloys showed more homogenous grain growth and only minor changes in the volume fraction of different texture components during annealing. The observed differences in the microstructure and texture formation during cold-rolling could be understood considering the differences in the stacking fault energy of the three alloys. On the other hand, the evolution of microstructure and texture of the quarternary and quinary alloys was affected by the sluggish diffusion behavior.

Effect of cold-rolling strain on the evolution of annealing texture of equiatomic CoCrFeMnNi high entropy alloy

The effect of cold-rolling strain on the evolution of microstructure and texture during annealing was studied in an equiatomic CoCrFeMnNi high entropy alloy. For this purpose the alloy was cold-rolled to 60%, 80% and 95% reduction in thickness. The three cold-rolled materials were isochronally annealed for 1h at temperatures ranging between 700°C and 1200 °C. With increasing rolling reduction, the texture transition from pure metal type (<60% reduction) to an alloy type texture (>80% reduction) was observed. The final recrystallized grain size was found to decrease systematically with increasing prior cold-rolling strain. However, the effect was much less pronounced below the annealing temperature of 1200°C due to sluggish diffusion in the HEA. The recrystallization texture of different deformed materials showed the presence of similar texture components indicating that prior deformation had only limited effect on the formation of annealing texture. The typical annealing texture components of low SFE materials, such as {236}<385> or {113}<332> were not the dominant components. The volume fractions of different texture components also did not reveal significant dependence on the annealing temperature. The evolution of annealing texture in the HEA could be adequately explained by the absence of strong preferential nucleation and growth.

Effect of Prior Recovery Treatment on the Evolution of Cube Texture During Annealing of Severely Warm-Rolled Al-2.5 wt pctMg Alloy

The effect of prior recovery on the evolution of cube texture ({001}〈100〉) in severely warm-rolled and annealed Al-2.5 wt pctMg alloy was studied. The Al-2.5 wt pctMg alloy was warm rolled to 97 pct reduction in thickness at 473 K (200 °C). The warm-rolled sheets were isochronally annealed for 1 hour at temperatures ranging from 523 K to 673 K (250 °C to 400 °C) without and with prior recovery treatments. In case of prior recovery, the sheets were pre-treated at 473 K (200 °C) for different time intervals ranging from 3.6 × 103 seconds (1 hour) to 8.64 × 104 seconds (24 hours) before the annealing. The warm-rolled alloy showed finely subdivided lamellar structure and strong presence of pure metal type texture. The annealed materials without any prior recovery treatment showed strong cube texture after annealing which could be attributed to the oriented nucleation of cube grains resulting from the preferentially recovered structure of cube regions in the warm-rolled state. In contrast, the cube texture was significantly weakened in materials subjected to different prior recovery treatments. The prior recovery treatments resulted in homogenous recovery which was confirmed by microstructural, textural, and conductivity measurements. Homogenous recovery eliminated the nucleation advantage of cube regions originating from the preferentially recovered structure and weakened the cube texture significantly. The present results indicated that prior recovery treatment could be effectively used to control recrystallization cube texture in severely warm-rolled aluminum alloys.

Evolution of microstructure and texture during annealing of Al-2.5%Mg-0.2%Sc severely deformed by a combination of accumulative roll bonding (ARB) and conventional rolling

Evolution of microstructure and texture during heavy cold-rolling and annealing of Al-2.5%Mg-0.2%Sc alloy was investigated. For this purpose recrystallized sheets of 1mm thickness having finely dispersed precipitates were processed to 3 cycles of ARB (equivalent strain, εeq=2.4) followed by conventional rolling to a final thickness of 200μm resulting in total equivalent strain of 4.0. Evolution of ultrafine microstructure and strong copper or pure metal type texture were observed during deformation. During annealing very stable microstructure was observed up to 400°C but further annealing resulted in formation of a layered microstructure with deformed layer sandwiched between recrystallized layers. Formation of strong cube texture is not observed in the recrystallized layers. Isothermal annealing for longer time at 500°C leads to abnormal growth of Q orientation ({013}<213>) within the deformed layer.

Deformation behavior of a Ni3Al(B,Zr) alloy during cold rolling: Part II. Microstructural and textural changes

Part I of this study described the changes in order and of structure during cold rolling of a Ni3Al(B,Zr) alloy. The textural and microstructural changes that occur during deformation are reported in this part. In addition to other features, a high density of shear bands start forming in this alloy from a rather early stage of deformation. The cold rolling texture of the material, which is basically of pure metal type at low strain levels, changes into alloy type after rolling between 35 and 45 pct. The maximum pole density of the alloy type texture is obtained at the {168}〈211〉 location. Transmission electron microscopy (TEM) micrographs show the presence of twins in the material from a deformation level of 35 pct onward, their density increasing with increase in deformation level. As has been proposed earlier, a structural transformation from L12 to DO22 appears to take place in the γ′ phase during rolling. This will change the deformation mode from primarily slip to twinning and this could be responsible for the observed textural change with rolling. The γ phase deforms by slip in a manner similar to a fcc material with high stacking fault energy. The final texture of the material actually reflects an aggregate of the components developed in the two phases.

Microstructure and texture evolution in ECAE processed A5056

Equal channel angular extrusion (ECAE) represents an effective means of microstructural refinement through severe plastic deformation. In aluminum based alloys microstructures obtained by this process generally result in interesting and remarkable combinations of mechanical properties, such as for instance enhanced strength together with high levels of ductility. In the present investigation, the evolution of the tensile properties, microstructures and crystallographic textures during ECAE has been studied for an Al-Mg based workhardening type alloy (A5056) by metallographic observation, transmission electron microscopy (TEM) and X-ray diffraction. The mechanical and microstructural characteristics of these alloys have been compared to extrudates of the same material prepared by conventional extrusion. The results show that dynamic recovery and the development of subgrains, mainly separated from each other by low angle grain boundaries, play an important role with respect to the formation of the ultrafine microstructures observed. No evidence for recrystallization and the nucleation of new grains occured up to pressing temperatures of 300°C and very sharp deformation textures were found to develop. Similar to rolling deformation a transition from a pure metal type texture to an alloy type texture in function of the deformation degree occurs. The formation of these ECAE-textures is discussed on the basis of the Taylor theory of polycrystalline deformation.

応力緩和挙動から導かれるB2型NiAl金属間化合物の高温変形機構

In order to study mechanisms of high temperature deformation of NiAl intermetallic compound with a B2-type crystal structure, internal stresses (σi) and effective stresses (σe) have been estimated by stress-relaxation tests conducted in the temperature region from 1223 to 1373 K. Two methods, i.e., Kikuchi’s method and Li’s method, are used to analyze the results of the relaxation behavior. The mobile dislocation densities remain constant during the relaxation tests in the temperature range tested so that Kikuchi’s method and Li’s method is relevant for analyzing the relaxation behavior of NiAl. The internal stresses and effective stresses estimated from the two methods are in relatively good agreement with each other. The ratio of internal stress σi to flow stress σs, (i.e., σi/σs) indicates that the flow stress includes the effective stress and that the pure metal type and alloy type high temperature deformation mechanisms coexist in high temperature deformation. Activation volume of the mobile dislocation is 102∼103b3, indicating that effective stress in NiAl is related to dragging stress of jogged screw dislocations. Thus mobile dislocations in NiAl at high temperatures move viscously as a result of the dragging stress acting on jogged screw dislocations and not as a result of the lattice friction associated with the Peierls stress.

純アルミニウム板の集合組織と成形性に及ぼす片ロール駆動冷間圧延の影響

Single roller driving cold-rolling (SRCR) was tried to develop the shear texture component {111}〈110〉 in pure aluminium, and the effect of the process on the texture development, r value and deep drawability was studied. The SRCR process, on the one hand, promotes the shear texture component {111}〈110〉 to some extent, and on the other hand, reduces the development of the pure metal type texture. The higher the reduction in thickness is, the more remarkable the effect of the SRCR process on the textural changes is. The shear texture component {111}〈110〉 almost disappears by subsequent annealing, suggesting that it may be unstable in the recrystallization process. Since the development of rolling texture in the SRCR processed sheets is weak, the recrystallization texture is considerably randomized, leading to \barr=0.8∼0.85 and Δr\fallingdotseq0. As a result, the SRCR processed sheet presents a large increase in the limit drawing ratio and very low earing height, in comparison with the conventionally cold-rolled sheet. It is suggested that perfect or inplane isotropy should be realized to improve deep drawability of aluminium and its alloy sheets, if the preferential development of the {111} texture component were unexpected.

Subboundary Characterization and Creep Deformation in Investment Cast Ti-48Al-2Nb-2Cr

AbstractSubgrain boundaries (subboundaries) in a creep deformed investment cast Ti-48Al-2Nb-2Cr specimen were characterized. A multi-stress drop test was performed at temperature 765 °C and stresses from 276 MPa to 103 MPa. The stress exponent n = 7. Subboundaries were observed both in equiaxed γ grains and within γ laths in lamellar grains. Dislocations within the subboundaries are characterized to be ordinary 1/2&lt;110] dislocations. Subboundaries are found to occur on many crystallographic planes and no preferred crystallographic planes are found for subboundary formation in the crept TiAl specimen. Misorientations across the subboundaries are less than 1°. Analysis of subboundary formation mode indicates that the creep deformation in TiAl is pure metal type.

Creep of niobium and solid solution strengthened Nb-1wt.%Zr

The search for new materials for advanced aerospace structural applications at elevated temperatures has renewed an interest in niobium and its alloys due to its high melting point (2741 K), low thermal neutron cross section, good corrosion resistance against liquid lithium, and low density (8. 58 gm/cc) compared to other refractory metals. However, the diffusivity of bcc niobium is high and, as a result, the creep strength of niobium is inherently weak. Solid solution strengthening is one approach to improve the creep strength of metallic materials. Solid solution strengthening of class M (pure metal type) materials changes the creep response and rate controlling deformation mechanism. Class M materials show a normal transient during the primary stage in a semilogarithmic plot of [dot [Epsilon]] versus [Epsilon] and the rate controlling mechanism is dislocation climb. Class A (alloy type) materials show an inverse transient during the primary stage in a [dot [Epsilon]] versus [Epsilon] semilogarithmic plot, and the rate controlling mechanism is viscous glide. The objective of this paper is to study and compare the creep behavior of niobium and Nb-1wt. %Zr.

Ｃｕ‐Ｎｉ‐Ａｌ合金の加工熱処理に及ぼすＴｉ添加の影響

The improvement of mechanical properties by a thermomechanical treatment (TMT) has been investigated on a Ti-added Cu-Ni-Al alloy. Characteristics in microstructure and rolling texture were examined in relation to the mechanical properties.In the thermomechanically treated Cu-Ni-Al-Ti alloy, the hardness, 0.2% proof stress and ultimate tensile strength reached the maximum values of 275Hv, 120kg/mm2 and 121kg/mm2, respectively.These values were much higher than those obtained in similarly treated Cu-Ni-Al alloys. The hardness increment of 100Hv obtained by cold rolling for the Cu-Ni-Al-Ni alloy was extremely higher than that of 60Hv for a Cu-Ni-Al alloy.The transmission electron microscopy of the preaged and cold rolled Cu-Ni-Al-Ti alloy indicated that deformation proceeded only in matrices and the concentrated stress in matrices leads mechanical twinning. X-ray pole figures on {111} reflection showed that the rolling texture was changed into an alloy type from a pure metal type observed in a Cu-Ni-Al alloy.

Deformation of cold-rolled wire-reinforced copper composites

Copper composites made by hot-pressing, and reinforced with nickel, molybdenum, tungsten and stainless steel wires, were cold-rolled and tested for their mechanical properties, microstructures, and orientation textures. The amount of reduction in rolling to wire instability was related to the work-hardening behaviour of both wire and matrix. The fibre lengths after multiple necking and fracture were related to the critical transfer length at fibre instability. Fibre fracture modes varied with matrix deformation mechanisms operative at various reductions. Strengthening in the direction of the wires followed ‘rule of mixtures’ predictions, but transverse strengthening was lower than predicted by theory. Matrix orientation textures were only slightly different from the pure metal type textures.

〈００１〉軸方位Ａｌ‐２ａｔ％Ｍｇ 合金単結晶の高温定常変形

Tensile tests on the <001> oriented single crystals were carried out at elevated temperatures from 623 to 873k to invertigate the deformation behavior. The deformation behavior changes from pure metal type to alloy type with increase in stress in a low stress region and vice versa in a high stress region. The stress exponent of steady state strain rate, n, is about 5 in the low stress region, about 3 in the middle stress region and 5 or more in the high stress region. The mobile dislocation density ih the steady state is expressed as: ρm=β(σ/μ)2 where σ is the applied stress, μ the shear modulus, and β depends on the deformation temperature. The general rate equation showing the relation between strain rate and steady state stress for the alloy type behavior is introduced.

Cu-Sn固溶体合金の高温定常変形

Polycrystals of Cu-Sn solid solutions containing 1 to 4 at%Sn were deformed in tension at temperatures of 823, 873 and 923 K and at strain rates of 1.7×10−5∼8.3×10−4 s−1. The results obtained are as follows:(1) In the steady state deformation stage the strain rate is represented by the relation-ship of \dotε∝σn, where n=3.1∼3.7 in high tin content alloys and n=4.7∼5.7 in low tin content alloys. The steady state deformation behaviour changes from a pure metal type (n∼5) to an alloy type (n∼3) with increasing tin content.(2) In the high concentration alloys showing an alloy type behaviour a work softening phenomenon was always observed. The high temperature deformation in these alloys is controlled by the dragging of solute atomosphere for dislocation motion.(3) In the low concentration alloys showing a pure metal type behaviour, the parameter m*, the effective stress sensitivity of dislocation glide velocity, was found to be 1.0∼2.5. In many cases except the region of high strain rate, the dislocation motion is viscous.(4) The steady state strain rate is independent of the stacking fault energy when n∼3, but depends on it when n∼5.(5) In the case that the dislocation velocity is proportional to the effective stress the method of determining the internal stress by stress relaxation test was examined. The results obtained by this method was approximately in accord with those by the dip test using an extrapolation technique.

The Development of Texture in Copper and Copper-Zinc Alloys

The crystallite orientation distribution function has been determined for cold-rolled copper, copper-10 per cent zinc and copper-30 per cent zinc ( α -brass) at cold reductions of 0, 20, 40, 60, 80, 90 and 95 per cent. The copper texture exhibits a steady development and contains a tube of orientations between limits which have previously been shown to be stable during multiple slip processes ( { 110 } 〈 112 〉 to { 4411 } 〈 11118 〉 ). The textures of the copper-zinc alloys both show a similar initial development to that of copper but a transition occurs above a reduction of about 40 per cent. This indicated that an additional deformation mode had become active. The features of the transition are consistent with those expected if the additional deformation mode were mechanical twinning. The development of the basic texture (pure-metal type) is in agreement with predictions based on the assumption of multiple slip conditions incorporating a considerable amount of cross-slip.

銅単結晶の圧延における(513)[\bar121]方位の挙動について

The copper single crystals with the (513)[\bar121] orientation which is an ideal orientation of the pure metal type rolling texture of fcc metals were rolled under various conditions. The strain rate dependence of the stability of this orientation during rolling was studied by means of the reflective electron-diffraction analysis of lattice rotation and the slip line observation using replica techniques.The single crystals were rolled such that the rolling direction was (1) normal to the transverse direction (TD) and (2) parallel to the longitudinal direction (LD), referred to undeformed crystals.In the case of the rolling referred to TD, the lattice rotation from (513)[\bar121] to (211)[\bar111] via \simeq(513)[\bar455] was observed independent of the strain rates of 10−1/sec and 102/sec. This orientation changes may be connected with the shape change of the crystal resulting from the deformation. These would seem to indicate that the orientation of (513)[\bar121] is not stable for a single crystal during rolling deformation. In the case referred to LD, on the other hand, the stability of the (513)[\bar121] orientation depended on the strain rates. At the low strain rate rolling (10−1/sec), the initial orientation was retained up to high reductions, while at the high strain rate rolling (102/sec), the lattice rotation toward (101)[\bar121] occured gradually. It was found from the slip line observation that there are no changes in active slip systems and no marked differences in slip band configurations except for the degree of the fragmentation of slip bands, in both strain rates. These results were discussed from the view-point of dislobation structures comparing with the reported models for the formation of the (513)[\bar121] ideal orientation.

銅単結晶の圧延における{211}&amp;lang;\bar111&amp;rang;方位の挙動について

In order to clarify the strain rate dependence of the stability of the {211}〈\bar111〉 orientation which is a second component of pure metal type rolling textures in fcc metals, the copper single crystals with the initial orientation (211)[\bar111] were rolled at room temperature at the rolling rates of 0.1 m/min and 100 m/min, which correspond to the strain rates of 10−1/sec and 102/sec respectively. The orientation changes during rolling were determined by the reflection electron diffraction method and the deformation substructures were observed by the transmission electron microscope. The results obtained are summarized as follows,(1) The stability of the (211)[\bar111] orientation during rolling depended on the strain rate.(2) At the low strain rate (10−1/sec), the initial (211)[\bar111] orientation was maintained until over 98% reduction.(3) At the high strain rate (102/sec), there were two different cases. First, the deviation from initial orientation to (513)[\bar121] was observed at about 30∼50% reduction. Secondly, the initial orientation was retained accompanying twinning deformation, and the (211)[\bar111]+(011)[100] orientations were developed at about 98% reduction.It may be concluded that these results are closely connected with the dynamical recovery due to the cross slip of screw dislocations and with the dynamic effects of the strain rate during rolling deformation.

On the Development of the Pure Metal Type Rolling Textures in &lt;I&gt;FCC&lt;/I&gt; Metals due to Slip Rotations

On the Development of the Pure Metal Type Rolling Textures in &lt;I&gt;FCC&lt;/I&gt; Metals due to Slip Rotations

(112)[1\bar10]方位を有する多結晶銅板の圧延によるすべり回転

Polycrystalline copper with a (112)[1\bar10] orientation was cold-rolled up to 85 pct and the slip rotations toward the stable end position was studied.The normal to the rolling plane rotates toward [\bar111] and the rolling direction toward [101]. After rolling of 85 pct, the rolling plane normal arrives at the vicinity of [\bar123] without passing [011] and the rolling direction approaches [2\bar11]. Then the pure metal type texture containing (\bar112)[1\bar11] as a minor component is developed. These slip rotations can be well explained as due to the operation of slip systems bearing the highest resolved shear stress and their cross slip systems. So, the minor component is considered to be described as an orientation near (\bar112)[2\bar11] rather than (\bar112)[1\bar11], since it is necessary that slip systems taking the rolling direction toward [1\bar11] must operate extensively to cause the orientation near (\bar112)[2\bar11] to displace to (\bar112)[1\bar11]. In consequence, the results obtained in the present work are not consistent with the theory of Dillamore et al. which proposed the pattern {011}〈211〉→{123}〈211〉→{112}〈111〉.