Copper Roll Research Articles

Effect of Cu-doping on the microstructure and magnetic properties of low-cost MM-Fe-B melt spun ribbons

In this paper, MM-Fe-B ribbons with different MM contents were prepared by melt spun technique at a fixed copper roll speed of 25 m/s. The maximum magnetic energy product of the MM15Fe78B7 ribbon is 9.22 MGOe and the coercivity is 6005 Oe. With the increase of MM contents, the coercivity of the magnet was increased, and the highest coercivity reached 9352 Oe in MM18Fe75B7. In addition, the microstructure and magnetic properties of Cu-doped MM15Fe78-xB7Cux (x = 0, 0.4, 0.6, 1 at.%) ribbons were systematically investigated. The results show that the introduction of Cu can suppress the formation of α-Fe soft magnetic phase in the melt spun ribbons. When the Cu content is 0.4 at.%, the grain size decreased from 61 nm to 44 nm, and the coercivity was improved from 6005 Oe to 8527 Oe, which is an increment of about 42 %, whereas the remanence and the magnetic energy product can remain basically unchanged. The addition of Cu element can not only refine the grain size, but also facilitate the enhancement of the homogeneity of the microstructure of the ribbons.

Effect of Roll Material on Strip Solidification between the Rolls of a Vertical-Type High-Speed Twin-Roll Caster

Tool steel for hot working is usually used for the rolls of conventional twin-roll casters for aluminum alloys. In a vertical high-speed twin-roll caster, copper rolls are used to rapidly solidify the aluminum alloys and to increase the casting speed, since the thermal conductivity of copper is higher than that of tool steel. However, the degree of superiority of copper rolls over steel rolls is not clear. In the present study, the effect of the roll material on strip solidification between the rolls of a vertical high-speed twin-roll caster was investigated by inserting a thermocouple in the strip during casting. The Al-4.8%Mg alloy was used, since it does not stick to the steel rolls in the absence of a parting material. Both copper rolls and mild steel rolls were used. The cooling rate, the supercooling of the liquidus temperature, and the temperature of the strip cast using the copper rolls were superior to those of that cast using the mild steel rolls. The copper rolls were better than the steel rolls in terms of achieving high-speed roll casting, rapid solidification of the strip, and high productivity.

Casting Process at Roll Bite in Strip Cast Using Vertical-Type High-Speed Twin-Roll Caster

The solidification process in strip casting using a vertical-type high-speed twin-roll caster was clarified by inserting a 0.1 mm diameter K-type thermocouple into a strip during casting. The roll speeds of the copper rolls were 10 m/min and 30 m/min, and the roll loads were 5 kN and 20 kN. Al-Si alloys with a Si content of 2%, 6%, and 12% were used to investigate the influence of latent heat and viscosity in the semisolid state. The strip temperature increased after exiting the rolls. This indicated that the inside of the strip had not completely solidified at the roll bite, and secondary cooling was necessary to rapidly solidify the inside of the strip. The distance from the roll bite to the solidification starting position ranged from 30 mm to 63 mm. The cooling rate and degree of supercooling increased as the Si content decreased. The cooling rate ranged from 400 °C/s to 4000 °C/s. The cooling rate and degree of supercooling decreased as the viscosity of the semisolid increased.

Twin Roll Caster for Clad Strip

Production of aluminum alloy clad strips requires many processes, and a reduction in the number of processes has long been demanded. A method to cast clad strips directly from molten metal using a twin roll caster with copper rolls is proposed in this work. Two types of twin roll casters were designed and tested. One was a vertical-type tandem twin roll caster and the other was a twin roll caster equipped with a scraper. The casting of the clad strips was conducted in an oxidizing atmosphere. The clad strips were cast at speeds higher than 15 m/min. This casting speed is much higher than that of conventional twin roll casters for aluminum alloys. The roll load was smaller than 0.2 kN/mm. This small roll load means that strips were not bonded by hot rolling. The clad strips had a clear interface between strips, and elements in each strip did not diffuse into other strips. The clad strips did not fracture at the interface in a tension shear test. This means that the clad strips were strongly bonded.

Calorimetric and structural analysis of the Zr–Fe–Co–B–Mo–W amorphous alloys doped with gadolinium

Abstract The paper presents the calorimetric and structural analysis of the rapidly solidified GdxZr10Fe58-xCo10B15Mo5W2 (where: x = 0, 1, 2, 3, 4, 5) alloy ribbons in as-cast state. The base alloys were obtained by the arc-melting of the high purity constituent elements under a low pressure of Ar protective atmosphere. Subsequently, the ribbon samples were produced by the single-roll melt spinning technique under the low Ar pressure at the linear velocity of the copper roll surface of 32 m/s. X-ray diffraction (XRD) studies have shown amorphous structure of all the alloy. The microstructure of the samples was examined by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) measurements were performed at various heating rates. These allowed to determine the thermal stability of the amorphous phase. The Kissinger, Ozawa and Augis-Bennett plots were constructed to determine the activation energies Ea for crystallization. The positron annihilation lifetime spectroscopy (PALS) was used to study the structural changes as well as a degree of disorder in the atomic structure caused by doping the base alloy with Gd.

Microstructure and mechanical properties of high-manganese-containing high-speed twin-roll cast Al-Mn-Si alloy strips and their cold-rolled sheets

Al-Mn based alloys with high-manganese content are expected to have improved mechanical properties due to solid solution hardening and/or dispersion hardening. However, the increase of Mn solubility of the alloy is difficult by using the conventional DC casting. In order to solve this problem, in the present study, we focused on the twin-roll casting method which is characterized by high cooling rates. Several kinds of high Mn-containing Al-Mn-Si alloy strips were fabricated by using a vertical-type high-speed twin-roll caster equipped with a pair of water-cooled copper rolls. Direct temperature measurement of the liquid melt during the casting was also performed. The alloy strips of various compositions containing up to 4 Mn and 2 Si (wt%) were successfully obtained. By observing the microstructure of the cross section of the strip, we found the characteristic solidified structure. The solidified structure consisted of three layers. Two solidified shells with a columnar dendrite structure grew from the roll surfaces toward the strip center. In the mid-thickness region, the band structure consisting of equiaxed dendrites and globular grains was observed between the solidified shells. Very fine primary particles were observed in the matrix near the strip surface, while, relatively coarse particles with blocky and needle-like shape were observed in the central band of the as-cast strip. The electric conductivity measurement was performed for the as-cast strips. Mn solubility in Al matrix was estimated from the obtained values. The estimated Mn solubility in the Al-2Mn-xSi strips was between 1.5 ~ 1.8wt% Mn. It was over 1.43wt%Mn for the Al-4Mn-xSi strips. We found that the Mn solubility of the as-cast strips was considerably high. The strips were cold-rolled to the sheets and then annealed at various conditions. They were subjected to the tensile tests, and the effects of solid solution hardening and dispersion hardening are discussed.

The Structure and Properties of Rapid Cooled Iron Based Alloy

In this paper we studied the structure of rapidly cooled alloy which composition was based on iron. Samples were prepared using arc melting under protective atmosphere of argon and then casted in the process of rapid cooling into water cooled copper mold. Samples of the same composition were also made using the liquid melt casting method on a spinning copper roll. The high purity samples in the form of rods and ribbons were obtained. As expected, the obtained samples were characterized by an amorphous structure as confirmed by Mössbauer spectroscopy and X-ray diffraction studies.

Microstructural Evolution of Al-Mn Based Alloy Fabricated by Vertical-Type High-Speed Twin-Roll Casting

For decades, twin-roll casting has been applied for manufacturing aluminum alloy sheets. This conventional process contributes to make thin aluminum sheets from the molten metal directly. Recently, vertical-type high-speed twin-roll casting (HSTRC) has been developed with much higher casting speed rather than the horizontal-type. Some modifications such as feeding nozzle and water-cooling system of copper rolls contribute to increase cooling rates. This characteristic leads to many metallurgical advantages like grain refinement, super-saturation of alloying elements and fine distribution of secondary particles. The objective of this study is to investigate the constituent particles in HSTRC aluminum alloy. The commercial Al-Mn alloy strip was successfully fabricated by HSTRC. Clearly different microstructure was found in thickness direction. Many constituent particles observed along the grain boundaries/cell boundaries as well as inside of Al matrix on the surface area, while eutectic structure around globular grain boundaries was observed in mid-central area. The morphology as well as chemical compositions of the constituent particles were investigated.

6000 Series Aluminium Alloy Strip Casting Using a Vertical Type Twin Roll Caster

A vertical type twin roll caster with two side dams was used to cast aluminium alloy strip with a thickness of about 5mm at speed higher than 10m/min. The characteristics of the twin roll caster with two side dams are as follows: The diameter of the copper roll is 500mm, the width of the copper roll is 110mm and the thickness of the copper roll sleeve is 25mm.The maximum casting speed is up to 60m/min. Using the vertical type twin roll caster, a 4.5mm thickness of 6111 strip could be cast at a speed of 30m/min. The microstructure of the as-cast strip was equiaxed and spherical, not columnar. The mechanical properties of the strip casted from the vertical type twin roll caster were almost as same as that of the strip made from the conventional cast ingot.

Experimental investigation of the influence of chip interference on burr height in machining micro V-grooves on electroplated copper roll die

The roll-to-roll imprinting technology is considered as the most promising process for manufacturing large-area microstructured surface in a high-precision, high-efficiency and low-cost way. However, the existence of cutting burr of microstructures on roll die will deteriorate the quality of microstructures on target surface in roll-to-roll imprinting processing. For electroplated copper material, this article presents the influence of chip interference on burr in cutting process. The parameter that illustrates the level of chip interference is deduced. The influences of cutting depth and included angle of V-shaped diamond tool on burr height of V-grooves are revealed by analyzing the chip interference. A series of experiments are carried out to verify the theoretical study. The results show good agreement between theoretical derivation and experimental analysis. The reason for chip interference of cutting process is made clear. Then, the optimal process of multi-step cutting process was given as the guidance to enhance the surface quality of micro V-grooves on electroplated copper roll die. With the optimal cutting parameters, the high-quality surface of micro-prism array is achieved.

急冷凝固Al-Mg-Si合金の機械的性質に及ぼす亜共晶Si量の影響

Rapidly solidified powders of Al-10 mass% Mg based alloys with or without additions of 1, 5 or 10 mass% Si were produced by atomizing and subsequent splat quenching on a water-cooled copper roll. Consolidation of the powders was done by cold pressing, vacuum degassing and hot extrusion (P/M materials). The microstructures of as-extruded P/M materials contained fine scale of intermetallic compounds. The size of the compounds in the Al-10Mg-1Si alloy was finer than that in the other alloys. The alloys containing excess Mg to the Mg2Si composition showed higher hardness and tensile strength than those containing excess Si to the Mg2Si composition at room temperature. Al-10Mg-1Si and Al-10Mg-10Si P/M materials showed the highest tensile strength of 480 MPa at room temperature and 140 MPa at 573 K, respectively.

Mechanical and Structural Characterization of Rapidly Solidified Al-Fe-Mg Alloys

Series of experiments on a series of Al-Fe-Mg alloys were performed to determine the effect of rapid solidification (RS) on the material strengthening, which result from the refining of thegrain size and intermetallic compound. Additionally, an enhancement of the material strengthening due to magnesium addition was also observed. Manufacture of RS Al-Fe-Mg alloys combined a spraydeposition of the molten alloy on the rotating water-cooled copper roll and plastic consolidation bymeans of powders pressing and hot extrusion methods. The results suggest that the rapid solidification provides an effective method of microstructure refinement and, in combination with solid solutionhardening due to Mg, leads to significant improvement of mechanical properties of Al-Fe-Mg based alloys.

An Analysis of the Microstructure and Mechanical Properties of Rapidly Solidified Al-1Fe-1Ni-5Mg Alloy

Experiments on Al-1Fe-1Ni-5Mg alloy were performed to determine the effect of rapid solidification (RS) on the material strengthening, which result from the refining of the grain size and intermetallic compounds. Additionally, an enhancement of the material strengthening due to magnesium addition was also observed. RS procedure was performed using spray deposition of the molten alloy on the rotating water-cooled copper roll. As a result, highly refined structure of rapidly solidified flakes was obtained. Using common powder metallurgy (PM) techniques, i.e. cold pressing, vacuum degassing and hot extrusion, as received RS-flakes were consolidated to the bulk PM materials. For comparison purposes, the conventionally cast and hot extruded Al-1Fe-1Ni-5Mg alloy was studied as well. RS process combined with hot pressing and extrusion procedure was found to be very effective method for the manufacture of fine grained material and effective refinement of intermetallic compounds. However some inhomogenity of particles distribution was observed, which was ascribed to varied cooling rate dependent on the particular spray-drop size. Mechanical properties of as-extruded material were examined using compression test at 293K – 873K. High strength and ductility of as-extruded RS material with respect to conventionally produced alloy were observed. However, the effect of enhanced mechanical properties of RS material is observed only at low deformation temperatures. It was found that increasing deformation temperature above 400K results in negligible hardening of RS samples if compared to conventionally produced material.

Casting of High-Aluminum-Content Mg Alloys Strip by a Horizontal Twin-Roll Caster

This study was aimed to investigate casting of high-aluminum-content Mg alloys strip by a horizontal twin-roll caster. A horizontal-type twin-roll caster was equipped with a nozzle. This nozzle was movable. The roll size was φ300 × W150, and copper rolls were used. The rolling road was very small. It was possible to cast AZ91D and AZ121 magnesium alloys continuously by a horizontal twin-roll caster. There was gloss and no crack. The thickness of as-cast strip of AZ91D was 4.5 mm and that of AZ121 was 4.6 mm, respectively. In the case that roll velocity was 48 m/min, the thickness of as-cast strip of AZ121 was 2.0 mm. A 2.0-mm-thick strip was able to coil, and the diameter was φ500 mm. The microstructures of the as-cast strip of AZ91D and AZ121 magnesium alloys were observed using light optical microscopy. Isometric dendrite crystals were observed at the as-cast strip. The as-cast strip without facing of AZ91D and AZ121 magnesium alloys were able to hot rolling of 75 pct reduction. The surface of the as-rolled sheet was flat and glossy. The tensile strength of the as rolled was 230 MPa and the elongation of as rolled was 4 pct.

Microstructure and mechanical properties of rapidly solidified/powder metallurgy Mg–6Zn and Mg–6Zn–5Ca at room and elevated temperatures

Rapid solidification/powder metallurgy (RS/PM) Mg–6Zn and Mg–6Zn–5Ca (wt.%) alloys in form of rods were prepared by hot extrusion with RS powders, produced via atomization of the alloy melt and subsequent splat-quenching between a couple of water-cooled copper rolls. The microstructure and mechanical properties of the alloys at both room and elevated temperatures were investigated. The results showed that with an addition of 5wt.%Ca to the Mg–6Zn alloy, the microstructure of the alloy was refined significantly, in which the grain size ranged from 500nm to 1μm and the number of finely dispersed particles increased substantially. This resulted in an increase in the compressive strength of alloy up to 408MPa at room temperature. Although the strength of both the alloys decreased with an increase in test temperature, the Mg–6Zn–5Ca alloy exhibited a high strength of 202MPa at 200°C, which resulted mainly from the formation of particles of the stable intermetallic phase Ca2Mg6Zn3, which were effective in pinning dislocations and grain boundaries at elevated temperatures. In addition, the formation of deformation twins and their intersections, and the interaction between the twins and the Ca2Mg6Zn3 particles during compressive deformation at 200°C contributed to the strengthening of the alloy. However, the Mg–6Zn alloy exhibited a very low strength of 41MPa at 200°C, which resulted from dynamic recrystallization softening.

Microstructure and magnetic properties of hard magnetic Pr9Fe52Co13Zr1Ti3B22alloy ribbons

In the present work the phase constitution, microstructure and magnetic properties of the Pr9 Fe52 Co13 Zr1 Ti3 B22 alloy ribbons in the as-cast state and subjected to short time annealing were investigated. The ribbons were obtained by melt-spinning technique (with the velocity of the copper roll surface of 15 m/s). Subsequently, the samples were annealed for 5 min at temperatures ranging from 923 to 1013K. The ribbon samples in as-cast state were fully amorphous and exhibited soft magnetic properties. Annealing at 923K resulted in partial devitrification of samples that has not changed considerably their magnetic properties. Heat treatment of specimens at higher temperatures caused the increase of volume fractions of hard magnetic phase, which was accompanied by significant changes of their hysteresis loops. The evolution of microstructure was studied by transmission electron microscopy TEM. Magnetic interactions between the grains of crystalline phases of selected samples were investigated basing on the deltaM plots determined from recoil curves.

Structural and Mechanical Features of Rapidly Solidified Al-2Fe-2Ni-5Mg Alloy

Rapid solidification (RS) of Al-2Fe-2Ni-5Mg alloy and following mechanical consolidation of powders by means of powder metallurgy (PM) methods was used with success to produce a bulk RS-material. RS powders were manufactured using an inert gas atomizing of the molten alloy and the spray deposition on the rotating water-cooled copper roll. Rods of 7 mm in diameter were received by means of the cold pressing of the flakes, vacuum degassing and hot extrusion method. For comparison purposes, the conventionally casted and hot extruded Al-2Fe-2Ni-5Mg alloy was tested as well. Mechanical properties of as-extruded materials were examined at 293 K – 873 K by compression tests performed at constant true strain rate of 5·10-3[s-1]. It was found that relatively high strength of as-extruded RS/PM material was accompanied by the high ductility of the samples deformed by hot compression tests. It was noticed that the most effective solution strengthening due to particles refining was observed at low deformation temperatures. Rising the test temperatures above ~ 420 K, was found to result in reduction of the flow stress to the values received for the industrial material (IM).The formation of coarse primary intermetallic compounds, which is typical for IM material, was effectively reduced for RS material. However some inhomogeneity of fine precipitates distribution in RS/PM material was observed. Nevertheless, it was considered that both solid solution hardening due to Mg addition and the dispersion strengthening due to refining of intermetallic compounds substantially increase the mechanical properties of the RS/PM material.

Roll Casting of Al-40%Sn-1%Cu Alloy Strip

In this study, the roll casting of Al-40%Sn-1%Cu alloy was tried by an unequal diameter twin roll caster. The unequal diameter twin roll caster could continuously cast the strip. The casting load of the roll was small to prevent the flow out of the Sn. The roll-load was 0.1kN/mm(unit width). The roll casting of 400mm-width strip of 8mm-thick was tried, and it was attained. The gravity segregation of Sn did not occur. The as-cast strip could be cold rolled down to 1mm. However, this strip had much porosity. The rapid solidification was useful to prevent the porosity. The copper roll was better than steel roll to increase cooling ability. The copper roll was suitable to prevent the porosity. The temperature of solidified metal was important factor which influenced the porosity. The 4mm-thickness strip with little porosity was could be cast at the speed of 30m/min.

Microstructure and Mechanical Properties of Rapidly Solidified Al-Fe-Ni-Mg Alloys

Rapid solidification (RS) combined with following mechanical consolidation of RS powders is considered as a valuable commercial method for the production of a wide range of metallic materials having fine-grained structures. Reported research results for various alloys demonstrate better compositional homogeneity, smaller grain size and relatively fine precipitates distributed homogenously in RS alloys than that for the materials produced by conventional metallurgical processing. The effect of rapid solidification on the microstructure and mechanical properties of selected Al-Fe-Ni-Mg alloys have been investigated. The basic item of the research work was obtaining aluminum PM materials strengthened by highly-dispersed transition metal compounds and aluminum-magnesium solid solution. Rapid solidification (RS) of Al-4Fe-4Ni and Al-4Fe-4Ni-5Mg alloys was performed by means of gas atomizing of the molten alloy and the spray deposition on the rotating water-cooled copper roll. Using typical powder metallurgy (PM) methods, i.e. cold pressing, vacuum degassing and hot extrusion, the RS-flakes were consolidated to the bulk PMmaterials. For comparison purposes, the conventionally cast and hot extruded Al-4Fe-4Ni and Al-4Fe-4Ni-5Mg alloys were studied as well. Mechanical properties of as-extruded materials were examined by compression tests performed at 293 K – 873 K. It was found that relatively high strength of as-extruded PM materials was accompanied by high ductility of samples deformed by hot compression test. Structural observations confirmed beneficial influence of rapid solidification on effective refining of intermetallic compounds, although some inhomogeneity of fine precipitates distribution was observed. Nevertheless, it was considered that an effective increase of the microhardness and strength of tested RS materials mostly result from achieved dispersion of structural components and can be intensified by solid solution hardening due to Mg-addition.

MECHANICAL PROPERTIES OF P/M MATERIALS OF RAPIDLY SOLIDIFIED Al-Co-Mg ALLOYS AT ELEVATED TEMPERATURES

With an aim of obtaining aluminum P/M materials strengthened by dispersion of transition metal compounds and solid solution of Mg , Al -2 mass % Co and Al -5 mass % Co alloys with varied Mg additions of 0, 1 and 5 mass% were prepared by rapid solidification techniques. Rapidly solidified flakes were produced by argon gas atomization and subsequent splat quenching on a water-cooled copper roll. The flakes were consolidated to the P/M (Powder metallurgy process is named as P/M) materials by hot extrusion after vacuum degassing. Cast ingots of these alloys were also hot-extruded under the same conditions to the I/M (Ingot metallurgy process is named as I/M) reference materials. Uniform dispersion of fine intermetallic compounds ( Co 2 Al 9) was observed in all the as-extruded P/M materials. Added Mg was present as the solute in the P/M and I/M materials alloy even after annealing at 773K. The P/M materials containing Mg exhibited higher hardness and strength than those without Mg at room temperature. Tensile strength increased with increasing amount of Mg in the I/M materials at elevated temperatures. However, strength of the P/M materials decreased with addition of Mg at 573K and 673K. According to the steady state creep rate and creep rapture time, the creep resistance of the P/M materials containing Mg was clearly inferior to that of Mg -free alloys. Thus the positive effects of Mg additions on mechanical properties of the P/M materials of Al - Co - Mg alloys disappeared at high temperature.