Research

11 pages, 1235 KiB

Open AccessArticle

Selection of Parameters and Strategies to Reduce Energy Consumption and Improve Surface Quality in EN-AW 7075 Molds Machining

by Oscar Rodriguez-Alabanda, Maria Trinidad Bonilla, Guillermo Guerrero-Vaca and Pablo Eduardo Romero

Metals 2018, 8(9), 688; https://doi.org/10.3390/met8090688 - 31 Aug 2018

Cited by 4 | Viewed by 2768

Abstract

The machining of cavities for blow molding is a long and costly process, with the objective of obtaining an excellent surface finish with the minimal possible electrical energy consumption (EEC). This work has studied which combination of cutting parameters and cutting strategies to [...] Read more.

The machining of cavities for blow molding is a long and costly process, with the objective of obtaining an excellent surface finish with the minimal possible electrical energy consumption (EEC). This work has studied which combination of cutting parameters and cutting strategies to use to achieve an optimum surface finish on the mold using the minimal associated EEC: in roughing operation, tool path strategy and axial depth of cut were studied; in finishing operation, tool path strategy, spindle-speed, feed-rate, and step-over were evaluated. Thirty-two molds were machined in blocks of aluminium alloy EN-AW 7075 T6 in a machining center of a three-axis, following an orthogonal design of experiments. The analysis of results demonstrates that: a roughing strategy has influence on the surface roughness on the bottom of the mold; a finishing strategy is an influential factor on the surface roughness on the walls of the mold; certain parameters have no relevance on the surface roughness but have an influence on the EEC; an adequate selection of cutting strategies and cutting parameters permit an improvement of surface roughness of up to 70%, and a reduction of 40% in EEC, compared to the less favorable tests. Full article

(This article belongs to the Special Issue Metallic Materials and Manufacturing)

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18 pages, 6335 KiB

Open AccessArticle

Effects of Sample and Indenter Configurations of Nanoindentation Experiment on the Mechanical Behavior and Properties of Ductile Materials

by Seyed Saeid Rahimian Koloor, Atefeh Karimzadeh, Mohd Nasir Tamin and Mohd Hamdi Abd Shukor

Metals 2018, 8(6), 421; https://doi.org/10.3390/met8060421 - 05 Jun 2018

Cited by 27 | Viewed by 6581

Abstract

The nanoindentation test is frequently used as an alternate method to obtain the mechanical properties of ductile materials. However, due to the lack of information about the effects of the sample and indenter physical configurations, the accuracy of the extracted material properties in [...] Read more.

The nanoindentation test is frequently used as an alternate method to obtain the mechanical properties of ductile materials. However, due to the lack of information about the effects of the sample and indenter physical configurations, the accuracy of the extracted material properties in nanoindentation tests requires further evaluation that has been considered in this study. In this respect, a demonstrator ductile material, aluminum 1100, was tested using the Triboscope nanoindenter system with the Berkovich indenter. A 3D finite element simulation of the nanoindentation test was developed and validated through exact prediction of the structural response with measured data. The validated model was then employed to examine the effects of various test configurations on the load–displacement response of the sample material. These parameters were the different indenter edge-tip radii, different indentation depths, different sample tilts, and different friction conditions between the indenter and the material surface. Within the range of the indenter edge-tip radii examined, the average elastic modulus and hardness were 78.34 ± 14.58 and 1.6 ± 0.24 GPa, respectively. The different indentation depths resulted in average values for the elastic modulus and hardness of 77.03 ± 6.54 and 1.58 ± 0.17 GPa, respectively. The uneven surface morphology, as described by the inclination of the local indentation plane, indicated an exponential increase in the extracted values of elastic modulus and hardness, ranging from 71.83 and 1.47 GPa (for the reference case, θ = 0°) to 243.39 and 5.05 GPa at θ = 12°. The mechanical properties that were obtained through nanoindentation on the surface with 6° tilt or higher were outside the range for aluminum properties. The effect of friction on the resulting mechanical response and the properties of the material was negligible. Full article

(This article belongs to the Special Issue Metallic Materials and Manufacturing)

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17 pages, 46059 KiB

Open AccessArticle

Hot Deformation Behavior and Processing Map of Mg-3Sn-2Ca-0.4Al-0.4Zn Alloy

by Chalasani Dharmendra, Kamineni Pitcheswara Rao, Kalidass Suresh and Norbert Hort

Metals 2018, 8(4), 216; https://doi.org/10.3390/met8040216 - 27 Mar 2018

Cited by 9 | Viewed by 5234

Abstract

Among newly developed TX (Mg-Sn-Ca) alloys, TX32 alloy strikes a good balance between ductility, corrosion, and creep properties. This study reports the influence of aluminum and zinc additions (0.4 wt % each) to TX32 alloy on its strength and deformation behavior. Uniaxial compression [...] Read more.

Among newly developed TX (Mg-Sn-Ca) alloys, TX32 alloy strikes a good balance between ductility, corrosion, and creep properties. This study reports the influence of aluminum and zinc additions (0.4 wt % each) to TX32 alloy on its strength and deformation behavior. Uniaxial compression tests were performed under various strain rates and temperature conditions in the ranges of 0.0003–10 s⁻¹ and 300–500 °C, respectively. A processing map was developed for TXAZ3200 alloy, and it exhibits three domains that enable good hot workability in the ranges (1) 300–340 °C/0.0003–0.001 s⁻¹; (2) 400–480 °C/0.01–1 s⁻¹; and (3) 350–500 °C/0.0003–0.01 s⁻¹. The occurrence of dynamic recrystallization in these domains was confirmed from the microstructural observations. The estimated apparent activation energy in Domains 2 and 3 (219 and 245 kJ/mole) is higher than the value of self-diffusion in magnesium. This is due to the formation of intermetallic phases in the matrix that generates back stress. The strength of TXAZ3200 alloy improved up to 150 °C as compared to TX32 alloy, suggesting solid solution strengthening due to Al and Zn. Also, the hot deformation behavior of TXAZ3200 alloy was compared in the form of processing maps with TX32, TX32-0.4Al, TX32-0.4Zn, and TX32-1Al-1Zn alloys. Full article

(This article belongs to the Special Issue Metallic Materials and Manufacturing)

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14 pages, 27234 KiB

Open AccessArticle

Experimental Investigation of Laser Ablation Characteristics on Nickel-Coated Beryllium Copper

by Dongkyoung Lee

Metals 2018, 8(4), 211; https://doi.org/10.3390/met8040211 - 25 Mar 2018

Cited by 14 | Viewed by 5702

Abstract

As electronic products are miniaturized, the components of the spring contact probe are made very fine. Current mechanical processing may make it difficult to perform micro-machining with a high degree of precision. A laser is often used for the high precision micro-machining due [...] Read more.

As electronic products are miniaturized, the components of the spring contact probe are made very fine. Current mechanical processing may make it difficult to perform micro-machining with a high degree of precision. A laser is often used for the high precision micro-machining due to its advantages such as a contact-free process, high energy concentration, fast processing time, and applicability to almost every material. The production of micro-electronics using nickel-coated copper is rapidly increasing and laser material processing is becoming a key processing technology owing to high precision requirements. Before applying laser material processing, it is necessary to understand the ablation characteristics of the materials. Therefore, this study systematically investigates the ablation characteristics of nickel-coated beryllium copper. Key laser parameters are pulse duration (4~200 ns) and the total accumulated energy (1~1000 mJ). The processed workpiece is evaluated by analyzing the heat affected zone (HAZ), material removal zone (MRZ), and roundness. Moreover, the surface characteristics such as a burr, spatter, and roundness shapes are analyzed using scanning electron microscope (SEM). Full article

(This article belongs to the Special Issue Metallic Materials and Manufacturing)

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10 pages, 5864 KiB

Open AccessArticle

Microstructure, Texture Evolution and Magnetic Properties of Fe-6.5 wt. % Si and Fe-6.5 wt. % Si-0.5 wt. % Cu Alloys during Rolling and Annealing Treatment

by Zhaoyang Cheng, Jing Liu, Jiachen Zhu, Zhidong Xiang, Juan Jia and Yunjie Bi

Metals 2018, 8(2), 144; https://doi.org/10.3390/met8020144 - 22 Feb 2018

Cited by 4 | Viewed by 3738

Abstract

Sheets of Fe-6.5 wt. % Si and Fe-6.5 wt. % Si-0.5 wt. % Cu with the thickness of 0.3 mm have been produced by hot and warm rolling. The microstructure, texture evolution and magnetic properties of the two alloys were investigated. It was [...] Read more.

Sheets of Fe-6.5 wt. % Si and Fe-6.5 wt. % Si-0.5 wt. % Cu with the thickness of 0.3 mm have been produced by hot and warm rolling. The microstructure, texture evolution and magnetic properties of the two alloys were investigated. It was found that the addition of 0.5 wt. % Cu promoted the formation of shear bands during warm rolling, and enhanced the {110}<001> texture at surface layer and {111}<112> texture in the middle layer. After annealing treatment, a strong η fiber texture with a peak at {110}<001> was formed in the Fe-6.5 wt. % Si-0.5 wt. % Cu sample, while the Fe-6.5 wt. % Si sample was characterized by complex γ, η and λ fibers. The formation of dominating η fiber in the annealed Fe-6.5 wt. % Si-0.5 wt. % Cu sample is attributed to the shear bands formed in {111}<112> oriented grains. These shear bands in {111}<112> oriented grains acted as the nucleation sites of η oriented grains and promoted the growth of Goss oriented grains. The presence of strong η fiber with a peak at Goss in Fe-6.5 wt. % Si-0.5 wt. % Cu sample was the cause for the higher magnetic induction observed for this sample than for the Fe-6.5 wt. % Si sample. Full article

(This article belongs to the Special Issue Metallic Materials and Manufacturing)

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16 pages, 44224 KiB

Open AccessArticle

An Efficient Approach to Address Issues of Graphene Nanoplatelets (GNPs) Incorporation in Aluminium Powders and Their Compaction Behaviour

by Zeeshan Baig, Othman Mamat, Mazli Mustapha, Asad Mumtaz, Mansoor Sarfraz and Sajjad Haider

Metals 2018, 8(2), 90; https://doi.org/10.3390/met8020090 - 25 Jan 2018

Cited by 25 | Viewed by 5677

Abstract

The exceptional potential of the graphene has not been yet fully translated into the Al matrix to achieve high-performance Al nanocomposite. This is due to some critical issues faced by graphene during its processing such as the dispersion uniformity, structure damage, compatibility/wettability, and [...] Read more.

The exceptional potential of the graphene has not been yet fully translated into the Al matrix to achieve high-performance Al nanocomposite. This is due to some critical issues faced by graphene during its processing such as the dispersion uniformity, structure damage, compatibility/wettability, and low graphene embedding content in Al matrix. In the present work, a new integrative method was adopted and named as “solvent dispersion and ball milling” (SDBM) to address the issues above efficiently in a single approach. This strategy involves effective graphene nanoplatelets (GNPs) solvent dispersion via surfactant decoration and solution ball milling employed to polyvinyl alcohol (PVA) coated Al with various GNPs content (0.5, 1 and 1.5 wt. %). Flaky Al powder morphology attained by optimizing ball milling parameters and used for further processing with GNPs. Detailed powders characterizations were conducted to investigate morphology, graphene dispersion, group functionalities by FTIR (Fourier transform infrared spectroscopy) spectroscopy and crystallinity by powder XRD (X-ray diffraction)analysis. Compaction behaviour and spring back effect of the GNPs/Al powders was also investigated at different compaction pressure (300 to 600 Mpa) and varying GNPs fractions. In response, green and sintered relative density (%) along with effect on the hardness of the nanocomposites samples were examined. Conclusively, in comparison with the unreinforced Al, GNP/Al nanocomposite with 1.5 wt. % GNPs exhibited the highest hardness gives 62% maximum increase than pure Al validates the effectiveness of the approach produces high fraction uniformly dispersed GNPs in Al matrix. Full article

(This article belongs to the Special Issue Metallic Materials and Manufacturing)

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3938 KiB

Open AccessArticle

Guidelines for Selecting Plugs Used in Thin-Walled Tube Drawing Processes of Metallic Alloys

by Eva María Rubio, Ana María Camacho, Raúl Pérez and Marta María Marín

Metals 2017, 7(12), 572; https://doi.org/10.3390/met7120572 - 18 Dec 2017

Cited by 9 | Viewed by 7387

Abstract

In this paper, some practical guidelines to select the plug or set of plugs more adequate to carry out drawing processes of thin-walled tubes carried out with fixed conical inner plug are presented. For this purpose, the most relevant input parameters have been [...] Read more.

In this paper, some practical guidelines to select the plug or set of plugs more adequate to carry out drawing processes of thin-walled tubes carried out with fixed conical inner plug are presented. For this purpose, the most relevant input parameters have been considered in this study: the tube material, the most important geometrical parameters of the process (die semiangle,

α

, and cross-sectional area reduction,

r

) and the friction conditions (Coulomb friction coefficients,

μ_{1}

, between the die and the tube outer surface, and

μ_{2}

, between the plug and the tube inner surface). Three work-hardening materials are analyzed: the annealed copper UNS C11000, the aluminum UNS A91100, and the stainless steel UNS S34000. The analysis is realized by means of the upper bound method (UBM), modelling the plastic deformation zone by triangular rigid zones (TRZ), under the validated assumption that the process occurs under plane strain conditions. The obtained results allow establishing, for each material, a group of geometrical parameters, friction conditions, a set of plugs that make possible to carry out the process under good conditions, and the optimum plug to carry out the process using the minimum amount of energy. The proposed model is validated by means of an own finite element analysis (FEA) carried out under different conditions and, in addition, by other finite element method (FEM) simulations and real experiments taken from other researchers found in the literature (called literature simulations and literature experimental results, respectively). As a main conclusion, it is possible to affirm that the plug that allows carrying out the process with minimum quantity of energy is cylindrical in most cases. Full article

(This article belongs to the Special Issue Metallic Materials and Manufacturing)

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7837 KiB

Open AccessArticle

Experimental Investigation of Forming Forces in Frictional Stir Incremental Forming of Aluminum Alloy AA6061-T6

by B.T.H.T. Baharudin, Q.M. Azpen, Shamsuddin Sulaima and F. Mustapha

Metals 2017, 7(11), 484; https://doi.org/10.3390/met7110484 - 07 Nov 2017

Cited by 24 | Viewed by 7190

Abstract

The incremental sheet forming (ISF) process is an emerging flexible sheet-forming process, which is adequate for the manufacturing of unique or small-volume batches. Single-point incremental forming (SPIF) is the original technology of incremental sheet-forming processes. In this article, frictional stir-assisted SPIF was used [...] Read more.

The incremental sheet forming (ISF) process is an emerging flexible sheet-forming process, which is adequate for the manufacturing of unique or small-volume batches. Single-point incremental forming (SPIF) is the original technology of incremental sheet-forming processes. In this article, frictional stir-assisted SPIF was used to deform AA6061-T6 aluminum alloy. Experimental tests were conducted to measure the forming forces during this process for the concerned lightweight material. The influence of process parameters was investigated, which included tool rotation speed, feed rate, step size and tool diameter on the produced forming forces. A Taguchi technique for the design of experiment (DOE) and the varying wall angle conical frustum (VWACF) test was employed in this study. The results show that the rotation spindle speed was the most dominant parameter that affects the forming forces, followed by the step size, feed rate and tool diameter. In addition, the interaction between the feed rate and step size has a notable impact on the values of the forming forces. Full article

(This article belongs to the Special Issue Metallic Materials and Manufacturing)

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