Sheath Rolling Research Articles

Microstructure and Mechanical Properties of 3vol%CNT Reinforced Cu Matrix Composite Fabricated by a Powder in Sheath Rolling Method

Microstructure and Mechanical Properties of 3vol%CNT Reinforced Cu Matrix Composite Fabricated by a Powder in Sheath Rolling Method

Fabrication and Evaluation of 5 vol%CNT/Al Composite Material by a Powder in Sheath Rolling Method

A powder in sheath rolling method was applied to the fabrication of a carbon nano tube (CNT) reinforced aluminum composite. A 6061 aluminum alloy tube with outer diameter of 31 mm and wall thickness of 2 mm was used as a sheath material. A mixture of pure aluminum powder and CNTs with a volume content of 5% was filled in the tube by tap filling and then processed to an 85% reduction using multi-pass rolling after heating for 0.5 h at <TEX>$400^{\circ}C$</TEX>. The specimen was then further processed at <TEX>$400^{\circ}C$</TEX> by multi-pass hot rolling. The specimen was then annealed for 1 h at various temperatures that ranged from 100 to <TEX>$500^{\circ}C$</TEX>. The relative density of the 5vol%CNT/Al composite fabricated using powder in sheath rolling increased with increasing of the rolling reduction, becoming about 97% after hot rolling under 96 % total reduction. The relative density of the composite hardly changed regardless of the increasing of the annealing temperature. The average hardness also had only slight dependence on the annealing temperature. However, the tensile strength of the composite containing the 6061 aluminum sheath decreased and the fracture elongation increased with increasing of the annealing temperature. It is concluded that the powder in sheath rolling method is an effective process for fabrication of CNT reinforced Al matrix composites.

ARB법에 의해 강소성가공된 Al/SiCp입자분산복합재료의 미세조직 및 기계적 특성

The <TEX>$Al/SiC_p$</TEX> particle reinforced composite fabricated by a powder-in sheath rolling (PSR) method was severely. deformed by the accumulative roll-bonding (ARB) process. The ARB process was performed up to 8 cycles at ambient temperature without lubricant. The ARBed composite exhibited an ulbricant. grained structure similar to the other ARBed bulky materials. Tensile strength of the composite increased gradually with the number of ARB cycles, but from the 6th cycle it rather decreased slightly. These characteristics of the composite were somewhat different from those of Al powder compact fabricated by the same procedures. The difference in microstructure and mechanical properties between Al powder compact and the composite was discussed.

분말피복압연법에 의해 제조된 Al 분말성형체의 반복겹침접합압연

An aluminum powder compact consolidated by a powder-in sheath rolling (PSR) method was severely deformed by accumulative roll-bonding (ARB) process. The ARB process was performed up to 8 cycles at ambient temperature without lubrication. Optical microscope and transmission electron microscope observations revealed that microstructure of the ARB-processed Al powder compact is inhomogeneous in the thickness direction. The ultra-fine subgrains often reported in the ARB-processed bulky materials were also developed near surface of the Al powder compacts in this study. Tensile strength of the ARB-processed Al powder compact increased at the 1st cycle, but from the 2nd cycle it rather decreased slightly.

분말피복압연법에 의해 제조된 (SiC)p/Al 복합재료의 미세조직 및 기계적 성질

분말피복압연법에 의해 제조된 (SiC)_p/Al 복합재료의 미세조직 및 기계적 성질

분말피복압연법에 의해 제조된 Al/Al2O3복합재료의 가공열처리후의 기계적 성질 및 집합조직

분말피복압연법에 의해 제조된 Al/Al₂O₃복합재료의 가공열처리후의 기계적 성질 및 집합조직

분말시스압연법에 의해 제조한 Al/Al2O3복합재료의 미세조직 및 집합조직

Aluminum-based <TEX>$Al/Al_2O_3$</TEX> composites were fabricated by a powder-in sheath rolling method. A stainless steel tube with outer diameter of 12 mm and wall thickness of 1 mm was used as a sheath. A mixture of aluminum powder and <TEX>$Al_2O_3$</TEX> particles of which volume content was varied from 5 to 20%, was filled in the tube by tap filling and then rolled by 75% reduction in thickness at ambient temperature. The rolled specimen was then sintered at 56<TEX>$0^{\circ}C$</TEX> for 0.5 h. The mixture of Al powders and <TEX>$Al_2O_3$</TEX> particles was successfully consolidated by the sheath rolling. The <TEX>$Al/Al_2O_3$</TEX> composite fabricated by the sheath rolling showed a recrystallized structure, while unreinforced Al powder compact fabricated by the same procedure showed a deformed structure. The unreinforced Al powder compact was characterized by a deformation (rolling) texture of which main component is {112}<111>, while the <TEX>$Al/Al_2O_3$</TEX> composite showed a mixed texture oi deformation and recrystallization. The sintering resulted in recrystallization in Al powder compact and grain growth in the composite.

분말시스압연법에 의해 제조된 Al/Al2O3복합재료의 기계적 성질

The powder-in sheath rolling was applied to the fabrication of <TEX>$Al/Al_2O_3$</TEX> composite. A stainless steel tube with outer diameter of 12 mm and wall thickness of 1 mm was used as a sheath. Mixture of aluminum powder and <TEX>$Al/Al_2O_3$</TEX> particles of which volume content was varied from 5 to 20 vol.% was filled in the tube by tap filling and then rolled to 75% reduction at ambient temperature. The re]]ed specimen was sintered at 56<TEX>$0^{\circ}C$</TEX> for 0.5 hr. The <TEX>$Al/Al_2O_3$</TEX> composite fabricated by the sheath rolling and subsequent sintering showed the relative density higher than 0.96. The tensile strength of the composite increased with the volume content of <TEX>$Al_2O_3$</TEX> particles, and it reached a maximum of 90 MPa which is 1.5 times higher than unreinforced material. The elongation decreased with the volume content of <TEX>$Al_2O_3$</TEX> particles. It is concluded that the powder-in sheath rolling is an effective method for fabrication of <TEX>$Al/Al_2O_3$</TEX> composite.

분말시스압연법에 의해 제조된 알루미늄 분말성형체의 조직 및 기계적 성질

A nitrogen gas atomized aluminum powder was consolidated by powder-in sheath rolling method. A pure aluminum tube with outer diameter of 12 mm and wall thickness of 1mm was used as a sheath. The aluminum tube filled with the aluminum powder, first, was cold-rolled to the thickness of 6mm for performing, and then consolidated by the cold rolling and/or subsequent hot rolling at 360, 460 and <TEX>$560^{\circ}C$</TEX>. The aluminum powder compact fabricated by the sheath rolling showed high relative density more than 0.96 at any rolling conditions. The 0.2% proof stress increased with increasing hot rolling reduction and hot rolling temperature. Tensile strength was hardly affected by change in the hot rolling reduction, whereas it decreased with increasing hot rolling temperature. The powder compact showed the large elongation when cold rolling or hot rolling reduction was large. It was found that the sheath rolling was an effective method for consolidation of aluminum powder.

Thermomechanical behavior of Ti–25Pd–24Ni–1W shape memory alloy reinforced Ti matrix smart composites

A Ti-matrix composite reinforced by a TiPd-based shape memory alloy (SMA) with the composition of Ti–25at.%Pd–24at.%Ni–1at.%W was fabricated by sheath rolling of the SMA plates (whose austenite start temperature was 465 K) and Ti matrix plates, which were alternatively laminated and inserted in a SUS304 stainless steel pipe before rolling. Heat-treated sheath-rolled composite was found to have a multi-layered interface structure between the SMA plate and Ti plates. The thermomechanical behavior of the composite was investigated experimentally and analytically. The 0.5% yield stresses of the composite increased with increasing temperature at temperatures higher than A s(0). This stress behavior could be explained based on a one-dimensional analytical model. Hence, it can be concluded that the stress increase is caused by the accumulation of residual compressive stress formed in the matrix by a martensite-to-austenite transformation of the SMA during heating and the yield stress increase of the SMA at high temperature.

Corrosion behaviour of amorphous Ni–Cr–Nb–P–B bulk alloys in 6M HCl solution

Amorphous Ni–Cr–Nb–16P–4B bulk alloys highly corrosion-resistant in a 6 M HCl solution have been obtained by copper mould casting. The as-cast Ni–Cr–Nb–16P–4B alloys (Cr, Nb=5 or 10 at.%) of 1 mm diameter are composed of an amorphous single phase, and they are spontaneously passive in the 6 M HCl solution at 303 K. Their polarization curves are almost the same as those of the corresponding rapidly quenched amorphous alloy ribbons. A larger Ni–10Cr–5Nb–16P–4B bulk specimen of about 20×20×2 mm in size has been also prepared by consolidation of gas-atomized amorphous alloy powders by sheath rolling at 708 K, at which the alloy is in the super-cooled liquid state. Although X-ray diffraction pattern of the specimen revealed a halo, typical of amorphous structure, its corrosion resistance in the 6 M HCl is not as high as that of the as-cast one. After immersion of the sheath-rolled specimen in the 6 M HCl solution, spherical pit-like attacks have been observed on the surface, suggesting the presence of nanocrystalline precipitates locally. Thus, for the Ni–Cr–Nb–P–B alloys the formation of single amorphous phase appears to be necessary to have high corrosion resistance in aggressive environments.

Processing of TiPd shape memory alloy reinforced Ti-matrix composites and their mechanical properties

Ti and Ti-2Cu matrix composites reinforced by TiPd-based shape memory alloys (SMAs) were fabricated by sheath rolling of Ti or Ti-2Cu plates with TiPd fiber. Fibers of three TiPd SMAs were used as reinforcements. The Young's modulus of TiPd fiber increased with increasing temperature above austenite start temperature, A s. Good bonding between the fiber and matrix was obtained by heat treatment at 1123 K for 3.6 ks following sheath rolling at the same temperature. A multi-layered reaction region was formed in the vicinity of the interface between Ti or Ti-2Cu matrix and TiPd-based SMA fiber. Tensile tests were performed at various temperatures for Ti-2Cu matrix composites containing Ti–22Pd–27Ni–1W and Ti/Ti–25Pd–24Ni–1W fiber. It was found that the 0.5% offset stress of these composites increased with increasing temperature. This stress increase is mainly caused by residual compressive stresses generated in association with shape memory effects of the TiPd-based SMAs. Surface observations of fractured specimens showed that interfacial layers were fractured in a ductile fracture mode.

Fabrication and Refinement of 6061(p)/6063 Aluminum Laminate by Accumulative Roll-Bonding (ARB) Process

A 6061 aluminum powder compact is fabricated by sheath rolling method using 6063 aluminum tube as a sheath. Accumulative Roll-Bonding (ARB) process is applied to the powder compact for improvement of its mechanical properties. The ARB process of 8 cycles is performed at ambient temperature under unlubricated conditions without removing the 6063 sheath. The ARB process of 6061 solid aluminum sheet is also performed for comparison to the 6061 powder compact. The tensile strength of the 6061(p)/6063 laminate increases almost linearly with the number of ARB cycles, and reached the maximum of 465MPa at the 6th cycle, which is 2.3 times higher than that of the initial. The elongation drops abruptly at the 1st cycle, and remains at a constant value (about 7%) from the 2nd cycle to the 5th cycle. Both the strength and the elongation decrease with the number of cycles above the 6th cycle. On the other hand, the tensile strength of 6061 sheet increases with the number of cycles gradually. The increase in tensile strength per cycle is greater in the 6061(p)/6063 laminate than that in the ARBed 6061 sheet. This strengthening is probably due to the fine dispersed oxide which was at first oxide film on aluminum. The ultra-fine grains less than 500nm in diameter are developed in the 6061(p)/6063 laminate fabricated by ARB process.

Mechanical Properties of (SiC)p/Al Composite Fabricated by Sheath Rolling

Aluminum based MMC reinforced with SiC particles was fabricated by the sheath rolling method. A SUS304 stainless steel tube was used as a sheath. A tube was filled with a powder mixture of aluminum and reinforcement, reduced 75% in thickness by rolling at ambient temperature, and then sintered at 560°C for 1.8ks. The composite was thermomechanically treated to improve its mechanical properties. The results of the present study were compared to those of Al 2 O 3 /Al composite fabricated by the same method. A powder compact of which the relative density was above 0.95 was obtained by cold sheath rolling only. After sintering, the tensile strength of the composites increased with increasing volume fraction of SiC, and it reached a maximum of 100 MPa which was 67% higher than that of the unreinforced material. The elongation decreased monotonously with increasing volume fraction of SiC. Both the strength and the elongation for the composite were not improved by thermomechanical treatment. This means that the powder mixture had been consolidated already almost completely by the sheath rolling followed by sintering. The strengthening effect by reinforcement was also recognized at elevated temperatures.

Strengthening of Sheath-Rolled Aluminum Based MMC by the ARB Process

The Accumulative-Roll Bonding (ARB) process was applied to an aluminum based MMC fabricated by a sheath rolling method, in order to improve the mechanical properties. The 8 cycles of ARB were performed at ambient temperature under unlubricated conditions. The ARB process was also performed on the unreinforced material, for comparison with the composite sample. The tensile strength of the composite increases with the number of cycles up to 5 cycles of ARB, above which it decreases slightly. The tensile strength of the unreinforced material increases up to 2 cycles of ARB, above which it does not change. The strengthening in the composite by the ARB process is caused by the improvement in homogeneity of distribution of reinforcement particles with the number of cycles as well as work hardening of the matrix material, while the strengthening in the unreinforced material is only caused by work hardening. The drop in strength for both materials is caused by recovery or recrystallization. On the other hand, the elongation tends to greatly decrease after I cycle, but from 2 cycles it increases with the number of cycles for both materials. The unreinforced material shows an inhomogeneous microstructure along the thickness direction at lower cycles of ARB; having a finer grained structure near surface and bonded interfaces than the other area. However, the inhomogenity of microstructure vanishes gradually as the number of cycles increases. As a result, the microstructure after 8 cycles consists almost entirely of ultra-fine grains under 1 μm in diameter along the thickness direction. The ultra-fine grain initiate to develop at lower ARB cycle in composite than in unreinforced material. This is probably due to enhanced strain induced by locally accumulated deformation around reinforcement particles.

Fabrication of Al/Al&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt; Particle Reinforced Metal Matrix Composite by Sheath Rolling of Powder Mixture

An Al/Al 2 O 3 particle reinforced metal matrix composite was fabricated by sheath rolling of powder mixture. A stainless steel tube with the inner diameter of 10 mm and outer diameter of 12 mm was used as a sheath. Mixture of aluminum powder and Al 2 O 3 powder of which volume fraction was varied from 5 to 20% were filled in sheath and rolled to the reduction of thickness of 75% at ambient temperature. Rolled powder compact was sintered, and after sintering additionally rolled and annealed for improvement of mechanical properties. The powder mixture could be consolidated by sheath rolling at ambient temperature. Relative density of composite became more than 0.96. The strongest composite in the present process was obtained after additional cold rolling subsequent to sintering, while it had poor ductility. The strength and ductility of the sintered composite was improved by additional cold rolling and annealing. The strength of sintered composite and that of additionally rolled and annealed composite increased with increasing volume fraction of Al 2 O 3 particles. It became about one and a half times as that of unreinforced powder compact at the volume fraction of 20%. It is proved that the sheath rolling method is promising process for fabricating metal matrix composites on powder metallurgy route.

Consolidation of Nitrogen Gas Atomized Aluminum Powder by Sheath Rolling

Nitrogen gas atomized aluminum powder was consolidated by a powder-in sheath rolling method. Aluminum powder was filled in aluminum tube of 12 mm in outer diameter and 10 mm in inner diameter. The sealed tube containing powder was rolled to the thickness of 6 mm at ambient temperature for compaction and then consolidated by the combination of cold rolling and subsequent hot rolling at various temperatures ranging from 360 to 560°C. Rolling schedule is determined as to obtain flat bar with the thickness of 3 mm. The relative density of consolidated powder compact was more than 0.96. The mechanical property of powder compact was affected by rolling schedule and temperature. The strength of powder compact was comparable to that of bulk material. When cold reduction or hot reduction was large, the elongation of powder compact became large. However, elongation decreased with the combination of moderate cold and hot rolling. The interparticle bonding necessary for consolidation was accomplished during heating after cold rolling when large cold reduction is adopted. On the other hand, bonding is accomplished during and/or after hot rolling in large hot reduction. This method is promising for fabricating composite materials on the powder metallurgy route.

Fe-30Cr-5Al合金急冷凝固粉末シースロール固化材の機械的性質に及ぼす冷間加工の影響

Fe-30Cr-5Al合金急冷凝固粉末シースロール固化材の機械的性質に及ぼす冷間加工の影響

アルミニウム合金板圧延での耳割れ防止法

Edge cracking in sheet rolling often causes a lower yield due to edge trimming, surface damage of the sheet by fragments and sheet breakage in the case of tension rolling. Several methods to prevent edge cracking have been proposed. In sheath rolling, the sheet is sheathed with other material. In edge adhering rolling, a ductile material is adhered to the edges of the sheet, and in edge restraint rolling, the rolling machine is reconstructed so as to give the edge restraint.In this experiment, edge adhering rolling was applied to the relatively thick material like a slab. To prevent edge cracking, it is not necessary that the side plate adheres all over the edge, but it is enough that it adheres only at the sheet surface. It is considered that the lateral spread at the edge is restrained and tensile stress there is compensated by the adhered side plate.