Tensile properties and microstructural characteristics of indirect rheoformed A356 aluminum alloy

Bolouri, A.,Bae, J.W.,Kang, C.G. Elsevier Sequoia 2013 Materials science & engineering. properties, micro Vol.562 No.-

The effects of rheoforming parameters such as the rheoforming temperature and pressure on the tensile properties of H-shaped components were examined. An H-shaped component is useful for practical investigation into the influence of different wall thicknesses on the microstructural and mechanical properties. A simulation study on the effect of forming pressure on the die filling was conducted using the DEFORM-3D package, and the results were compared with that obtained using the actual rheoforming. The semisolid slurries were prepared by employing the electromagnetic stirring (EMS) technique. The components were rheoformed at different forming conditions and their tensile properties in the center and side positions were evaluated and linked to the corresponding microstructure. The tensile properties remained approximately constant when the rheoforming temperature was increased from 580<SUP>o</SUP>C to 590<SUP>o</SUP>C, but was followed by a substantial reduction at 600<SUP>o</SUP>C. Moreover, the tensile properties in the center and side positions were distinct. Increasing the rheoforming pressure from 200MPa to 250MPa had a harmful effect on the elongation values, whereas the effect on the ultimate tensile strength values was limited. This trend could be linked to the increase in prevalence of internal defects such as the liquid segregation.

Effect of strain rate on the defect susceptibility of tensile properties to porosity variation

Lee, Choongdo,Youn, Jeongil,Kim, Youngjig Elsevier 2017 Materials science & engineering. properties, micro Vol.683 No.-

<P><B>Abstract</B></P> <P>The contribution of the strain rate to the dependence of tensile properties on the microporosity variation in A356 casting alloy was investigated in terms of the defect susceptibility of tensile properties to the microporosity variation with variations of the strain rate as well as the relative contribution of microporosity and strain rate to overall tensile properties. The test samples were prepared using a low-pressure die-casting process and subsequent T4 treatment (12-h at 540°C), and the tensile test was carried out at room temperature for strain rates varying in the 1.4×10<SUP>−4</SUP>∼1.4×10<SUP>−1</SUP> s<SUP>−1</SUP> range. The overall dependence of tensile properties on the strain rate is not described precisely owing to remarkable deviations in the data that mainly arose from the variation of the fractographic porosity; these deviations can be clearly attributed to the variability in the defect susceptibility coefficient of the tensile properties to the microporosity variation. The defect susceptibility coefficient of ultimate tensile strength (UTS) to microporosity variation increases with the strain rate, whereas the defect susceptibility coefficient of elongation decreases. Although the UTS for the sample with a low microporosity level increases with increasing strain rates, the UTS above a certain porosity level is affected adversely and decreases with the increasing strain rates. However, the nominal level of tensile elongation on the variation of the strain rate clearly decreases with the increase of the microporosity. The fractographic porosity practically decreases with the increase of the strain rate, and the overall fracture path between the micro-voids depends practically upon a certain transition of the fracture mode of Si particles accompanying the variation of the strain rate. Additionally, the damage evolution of eutectic Si particles is transited from a mixed mode of cracking and debonding failure to a failure mode which the debonding failure dominates as the strain rate increases.</P>

Tensile and Corrosion Properties of Anodized Ultrafine‑Grained Ti–13Nb–13Zr Biomedical Alloy Obtained by High‑Pressure Torsion

Dragana Barjaktarević,Bojan Medjo,Primož Štefane,Nenad Gubeljak,Ivana Cvijović‑Alagić,Veljko Djokić,Marko Rakin 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

Severe plastic deformation (SPD) is a popular group of techniques applied to achieve the nanostructuring of the metallic biomaterials and improvement of their mechanical characteristics. One of the most commonly used SPD methods is the highpressure torsion (HPT) technique which enables the obtainment of the microstructure with small grains and high strength. In the present study, the influence of the plastic deformation and surface modification treatment on the tensile and corrosion properties of the Ti–13Nb–13Zr (wt%) alloy is investigated. In that purpose, the coarse-grained (CG) Ti–13Nb–13Zr (TNZ) alloy was subjected to the HPT processing by applying a pressure of 4.1 GPa with a rotational speed of 0.2 rpm and 5 revolutions at room temperature to obtain the ultrafine-grained (UFG) microstructure. The alloy microstructure before and after HPT processing was analysed using the scanning electron microscopy (SEM) and the X-ray diffraction (XRD). The homogeneity of the UFG TNZ alloy was determined by microhardness testing and microscopic observations. The nanotubular oxide layer on the surface of the TNZ alloy, both in CG and UFG condition, was formed by electrochemical anodization in 1 M H3PO4 + NaF electrolyte for 90 min. SEM analysis was used to characterise the morphology of the anodized surfaces, while energy dispersive spectroscopy was applied to determine the chemical composition of the nanostructured layers formed at the alloy surfaces. Mechanical properties of the TNZ alloy, before and after HPT processing and electrochemical anodization, were determined by tensile testing. After tensile testing, the fractographic analysis was conducted to identify the fracture mechanisms. The potentiodynamic polarization technique was used to determine the corrosion resistance of the alloy before and after plastic deformation and surface modification treatment. The obtained results showed that the alloy is reasonably homogeneous after the HPT processing. The XRD analyses reviled the presence of α′ and β phases in the CG TNZ alloy microstructure, while the additional ω phase was detected in the microstructure of the UFG TNZ alloy. The HPT obtained alloy exhibits higher hardness and improved tensile properties than the alloy in the as-received CG condition, while the electrochemical anodization leads to a decrease of its mechanical properties. Both CG and UFG alloys show excellent corrosion stability in Ringer’s solution. Moreover, electrochemical anodization leads to a decrease or an increase of the corrosion resistance of these materials, depending on the morphology of the formed nanotubular surface layers. The results indicate that the anodized CG TNZ alloy is characterized by a lower modulus of elasticity and better corrosion resistance properties than the anodized UFG TNZ alloy.

Prediction of the mechanical properties of granites under tension using DM techniques

Martins, Francisco F.,Vasconcelos, Graca,Miranda, Tiago Techno-Press 2018 Geomechanics & engineering Vol.15 No.1

The estimation of the strength and other mechanical parameters characterizing the tensile behavior of granites can play an important role in civil engineering tasks such as design, construction, rehabilitation and repair of existing structures. The purpose of this paper is to apply data mining techniques, such as multiple regression (MR), artificial neural networks (ANN) and support vector machines (SVM) to estimate the mechanical properties of granites. In a first phase, the mechanical parameters defining the complete tensile behavior are estimated based on the tensile strength. In a second phase, the estimation of the mechanical properties is carried out from different combination of the physical properties (ultrasonic pulse velocity, porosity and density). It was observed that the estimation of the mechanical properties can be optimized by combining different physical properties. Besides, it was seen that artificial neural networks and support vector machines performed better than multiple regression model.

고령사회에 대비한 노인 건강 의류 제품 개발을 위한 기초 연구 -니트 소재 압박복을 중심으로-

박명자 ( Myung Ja Park ),상정선 ( Jeong Seon Sang ) 복식문화학회 2011 服飾文化硏究 Vol.19 No.2

A study on compressive garments guarantee the required pressure and form depending on the type of disease and the state of injury can be used in the preventive treatment of cardiovascular disease. This research is to provide a preliminary data to develop medical clothing products, especially knitted compression garments. Starling from analyzing knitted structure of imported pressure goods to apply to test samples, 11 kinds of knitted stretchy fabrics were manufactured under the various knitting conditions, then their tensile, mechanical and hand properties were measured. In comparison size changes by knitting structure, luck stitch applied structure showed an increase in course direction and decrease in wale direction. Float stitch applied structure indicated the contraction of size in width because of unformed loops and floated yam on the technical back of fabric. As a result of tensile properties in tuck and float applied structure, tensile strength was increased in the course direction. On the other hand, the more loops overlapped due to the tuck and float stitch, the more decreased their elongation and elastic recovery were. In case of mechanical properties, as the tuck and float stitch were overlapped double or triple the bending and shearing properties were risen. Accordingly, the drape of fabric becomes stiff, and its surface becomes rough and uneven. The measurements of hand properties showed that the value of KOSHI, FUKURAMI NUMERI in tuck and float applied structure are higher than the plain structure. This results from the relationship between the mechanical and hand properties.

고용 강화 및 결정립 미세화를 통한 마그네슘 합금 주조재의 기계적 물성 향상

김상훈,문병기,유봉선,박성혁 한국주조공학회 2017 한국주조공학회지 Vol.37 No.6

This study investigated the effects of the addition of Zn, Ca, and SiC on the microstructure and mechanical properties of Mg-Al alloys. The tensile properties of homogenized Mg-xAl (x = 6, 7, 8, and 9 wt.%) alloys increased with increasing Zn content by the solid-solution strengthening effect. However, when the added Zn content exceeded the solubility limit, the strength and ductility of the alloys decreased greatly owing to premature fracture caused by undissolved coarse particles or local melting. Among the MgxAl- yZn alloys tested in this study, the AZ74 alloy showed the best tensile properties. However, from the viewpoints of the thermal stability, castability, and tensile properties, the AZ92 alloy was deemed to be the most suitable cast alloy. Moreover, the addition of a small amount (0.17 wt.%) of SiC reduced the average grain size of the AZ91 alloy significantly, from 430 μm to 73 μm. As a result, both the strength and the elongation of the AZ91 alloy increased considerably by the grain-boundary hardening effect and the suppression of twinning behavior, respectively. On the other hand, the addition of Ca (0.5-1.5 wt.%) and a combined addition of Ca (0.5-1.5 wt.%) and SiC (0.17 wt.%) increased the average grain size of the AZ91 alloy, which resulted in a decrease in its tensile properties. The SiC-added AZ92 alloy exhibited excellent tensile properties (YS 125 MPa, UTS 282 MPa, and EL 12.3%), which were much higher than those of commercial AZ91 alloy (YS 93 MPa, UTS 192 MPa, and EL 7.0%). The fluidity of the SiC-added AZ92 alloy was slightly lower than that of the AZ91 alloy because of the expansion of the solid-liquid coexistence region in the former. However, the SiC-added AZ92 alloy showed better hot-tearing resistance than the AZ91 alloy owing to its refined grain structure.

Green Composites. I. Physical Properties of Ramie Fibers for Environment-friendly Green Composites

Nam Sung-Hyun,Netravali Anil N. The Korean Fiber Society 2006 Fibers and polymers Vol.7 No.4

The surface topography, tensile properties, and thermal properties of ramie fibers were investigated as reinforcement for fully biodegradable and environmental-friendly 'green' composites. SEM micrographs of a longitudinal and cross sectional view of a single ramie fiber showed a fibrillar structure and rough surface with irregular cross-section, which is considered to provide good interfacial adhesion with polymer resin in composites. An average tensile strength, Young's modulus, and fracture strain of ramie fibers were measured to be 627 MPa, 31.8 GPa, and 2.7 %, respectively. The specific tensile properties of the ramie fiber calculated per unit density were found to be comparable to those of E-glass fibers. Ramie fibers exhibited good thermal stability after aging up to $160^{\circ}C$ with no decrease in tensile strength or Young's modulus. However, at temperatures higher than $160^{\circ}C$ the tensile strength decreased significantly and its fracture behavior was also affected. The moisture content of the ramie fiber was 9.9 %. These properties make ramie fibers suitable as reinforcement for 'green' composites. Also, the green composites can be fabricated at temperatures up to $160^{\circ}C$ without reducing the fiber properties.

Effects of Mn and Mo addition on high-temperature tensile properties in high-Ni-containing austenitic cast steels used for turbo-charger application

Jung, Seungmun,Jo, Yong Hee,Jeon, Changwoo,Choi, Won-Mi,Lee, Byeong-Joo,Oh, Yong-Jun,Kim, Gi-Yong,Jang, Seongsik,Lee, Sunghak. Elsevier Sequoia 2017 Materials science & engineering Structural materia Vol.682 No.-

<P><B>Abstract</B></P> <P>Since turbo-chargers require more excellent high-temperature properties to maintain their structures at further higher exhaust gas temperatures up to 1050°C, a 20wt%-Ni-containing austenitic cast steel (N20 steel) has been suggested as a promising candidate cast steel. However, this steel is very expensive because it contains a large amount of expensive Ni. In order to partly replace expensive Ni by inexpensive Mn and to improve high-temperature tensile properties in the N20 steel, three austenitic cast steels were fabricated by replacing 6wt% of Ni by 6.9wt% of Mn or by adding 2–4wt% of Mo. Thermodynamically calculated fractions of equilibrium phases (austenite, ferrite, and M<SUB>7</SUB>C<SUB>3</SUB> carbide) were matched with experimentally measured fractions, although they were somewhat overestimated. The N14 steel where 6wt% Ni was replaced by 6.9wt% of Mn did not contain any ferrite, and showed comparable or more excellent high-temperature tensile properties than those of the N20 steel, which indicated the successful replacement up to 6wt% Ni by Mn, together with alloying cost reduction of 10%. The Mo addition also favorably affected high-temperature properties because Mo worked for increasing both M<SUB>7</SUB>C<SUB>3</SUB> fraction and austenite matrix hardness. Simultaneously considering mechanical properties and alloying costs, therefore, these Mo-containing N14 steels can be fully adopted for high-performance turbo-chargers requiring excellent high-temperature properties.</P>

구상흑연주철 FCD60과 Cr-Mo강 SCM440 확산접합부의 인장성질에 미치는 접합조건의 영향

송우현,김정길,강정윤 대한용접접합학회 2004 대한용접·접합학회지 Vol.22 No.1

The effect of bonding condition on tensile properties of joints diffusion bonded spheroidal graphite cast iron, FCD60 to Cr-Mo steel, SCM 440 was investigated. Diffusion bonding was performed with various temperatures, holding times, pressures and atmospheres. All tensile specimens were fractured at the bonding interface. The tensile strength and elongation was increased with increasing bonding temperature. Especially, tensile strength of joints bonded at 1123K was higher than that of a raw material, FCD60, and tensile strength of joints bonded at 1173K was equal to that of a raw material, SCM440, but elongation of all joints was lower than those of raw materials. There was little the effect of holding time on the tensile properties. In comparison with bonding atmosphere, the difference of tensile strength was not observed, but elongation of joint bonded at vacuum(6.7mPa and 67mPa) was higher than that of Ar gas. Higher the degee of vacuum, elongation increased. Tensile properties of diffusion bonds depended on microstructures of cast iron at the interface and void ratio. Microstructures of cast iron at interface changed with temperature, because decarburizing and interdiffusion at the interface occurs and transformation of austenite-1 ferrite + graphite occurs on the cooling process. The void ratio decreased with increasing temperature, especially, effected on the elongation.

Effect of Clay Type and Concentration on Optical, Tensile and Water Vapor Barrier Properties of Soy Protein Isolate/Clay Nanocomposite Films

Jong-Whan Rhim 한국포장학회 2009 한국포장학회지 Vol.15 No.3

Soy protein isolate (SPI)-based nanocomposite films with three different types of nanoclays, such as Cloisite Na+, Cloisite 20A, and Cloisite 30B, were prepared using a solution casting method, and their optical, tensile, and water vapor barrier properties were determined to investigate the effect of nano-clay type on film properties. Among the tested nanoclays, Cloisite Na+, a hydrophilic montmorillonite (MMT), exhibited the highest transparency with least opaqueness, the highest tensile strength, and the highest water vapor barrier properties, indicating Cloisite Na+ is the most compatible with SPI polymer matrix to form nanocomposite films. The film properties of SPI/Cloisite Na+ nanocomposite films were strongly dependent on the concentration of the clay. Film properties such as optical, tensile, and water vapor barrier properties improved significantly (p<0.05) as the concentration of clay increased. However, the effectiveness of addition of the clay reduced above a certain level (i.e., 5wt%), indicating that there is an optimum amount of clay addition to exploit the full advantage of nanocmposite films.