Effect of shielding gas on microstructure and mechanical properties in AA6061-T6 alloy MIG welding

Due to its properties such as high strength/weight ratio, enhanced corrosion resistance, low density, AA6061-T6 aluminum alloy welding is widely used in structural, automotive and rail industry. In this study, AA6061-T6 alloy was welded with robotic metal inert gas technique using ER5356 filler wire. The effects of different shielding gas composition ratios (argon/helyum) on the macro / microstructre, mechanical properties (hardness, tensile strength) of the weld joint were investigated. Welding porosity decreased with the addition of helium gas to argon gas. Accordingly, the tensile strength of welded joints increased from 190 MPa to 221 MPa with the addition of helium gas. The strength of the welded joints (190-221 MPa) was obtained lower than that of the base material (290 MPa) due to the changes in the microstructure as a result of the weld thermal cycle and grain coarsening in the heat affected zone. Dentritic, columnar and coarse shaped grains were observed along the weld section, respectively in the weld bead, partially melted zone and heat affected zone. The differentiation of the shielding gas composition did not cause these regions to change, but the heat affected zone expanded with the increase in the helium content. The change in hardness of the cross section of welded joint has increased from around 60 HV to 90 HV from the welding area to the base material. 25% Argon-75% Helium gas mixtures provided optimum combination in terms of microstructure, mechanical properties and cost

Experimental Investigation of Sheet Metal Forming Using a Recyclable Low Melting Point Alloy Tool

Due to intense competition in automotive industry, new car models have to be launched as quickly as possible. A re-evaluation of the design and development phases has reshaped product development in order to get product earlier than competitors. Prototype production is one of the longest stages of product development due to physical verification activities. Shortening of this process will provide more opportunity to get project schedule earlier. Rapid prototype technologies are usually used as a guide for visual and packaging analysis. However, there is a requirement to use these parts for functional testing as well. Developing alternative rapid tooling methods which shorten the physical prototype production phase, while adequately supporting visual, packaging and functional aspects of sheet metal forming, can lead to considerable savings in vehicle prototype development. In this study, sheet metal prototype part using recyclable low melting point alloy was experimentally investigated by analysing dimensional conformance of tools and parts. In addition to wear performance, thickness reduction was investigated for stamped parts. Abstract in German: Untersuchung der Metallblechumformung unter Verwendung eines recyclingfähigen Werkzeuges aus einer niedrigschmelzenden Legierung. Aufgrund des intensiven Wettbewerbs in der Automobilindustrie müssen neue Fahrzeugmodelle so schnell wie möglich auf den Markt gebracht werden können. Um ein Produkt früher als die Wettbewerber fertig zu haben, wurde die Produktentwicklung durch eine Re-Evaluierung des Designs und der Entwicklungsphasen verändert

Sintering of a boron-doped injection moulded 17-4PH stanless steel

Powder injection molding (PIM) is an attractive process to produce complex, near-net shaped components. The process overcomes the shape limitation of traditional powder compaction, the cost of machining, the productivity limits of isostatic pressing and slip casting, and the defect and tolerance limitations of conventional casting. Over 50% of the injection molded and sintered components are made from stainless steel composition [1–3]. The alloy 17-4 PH stainless steel powders—a precipitation-hardening martensitic stainless steel, shaped and processed via injection molding can achieve high complexity of part geometrical with mechanical and corrosion properties, similar or superior to wrought material. Due to its high strength and good corrosion resistance 17-4 PH has widespread applications, especially in medical, automotive, military, and aerospace instruments [4–6]. Earlier investigations on PM or PIM 17-4 PH focused on the effect of powder characteristics, sintering atmosphere, sintering temperature, sintering time, heat treatment, residual carbon content on microstructure, corresponding microstructural characterization, mechanical and corrosion properties [4–6]. In several investigations boron as a sintering additive has been used to achieve higher sintered density in stainless steels at lower sintering temperatures [7–9]. As a consequence, a noticeable improvement in the mechanical properties is obtained. Boron can be added either in its elemental form (both amorphous and crystalline) or as a compound (for example, Fe2B, BN, NiB, and CrB). A small particle size of the additive is desirable to obtain a uniform dispersion. Boron additions increase hardenability in steels, increase strength (via increase in sintered density), improve grain boundary cohesive strength, enhance corrosion resistance, and improve ductility [7, 9]. The aim of this study is to investigate the effect of added boron on the sintering behavior and final properties of powder injection molded 17-4 PH stainless steel. In this research, gas atomized 17-4 PH stainless steel powders (Fe-16.2Cr-4.6Ni-4.6Cu-0.54Mn0.30Nb-0.30Si-0.095Mo-0.038C-0.026P-0.002S) provided by Osprey Metals Ltd. were used. It has particle size distribution of D10 = 3.25 µm, D50 = 10.6

Metalik Biyo-Uyumlu Stentlerin Gelişim Süreci

Stent, çeşitli nedenlerle engellenen damarlar için yapay bir koridor açmak, bu bölgede destek yapısı oluşturarak tıkanıklığı gidermek amacıyla kullanılan elemanlara verilen isimdir. Polimerik ve metalik içerikli biyo-uyumlu malzemelerin geliştirilmesi ve yaygınlaşması, stent uygulamalarındaki başarının artmasına neden olmaktadır. Günümüzde nitinolden imal edilen metal stentler yaygın olarak kullanılmakla birlikte, biyo-bozunur metal stentler konusunda araştırmalar devam etmektedir. Bilindiği üzere stentin görevi, implantasyondan sonraki 6-12 aylık evreden sonra tamamlanmakta ve bu süreden sonra herhangibir işlevi kalmamaktadır. Ancak kalıcı stentler bu süre tamamlandıktan sonra da vücut içerisinde kalmakta ve zaman zaman komplikasyonlara neden olmaktadır. Bu amaca yönelik aday malzemelerin, stent üretiminde kabul görmüş 316L paslanmaz çeliklerin mekanik özelliklerine sahip olması, biyo-bozunur olması ve kendisinin ve bozunan ürünlerin toksik etkiye sahip olmaması beklenmektedir. Bu makale, son 15 yılda biyo-bozunur stentler için metalik içeriğe sahip materyallerin tasarımında ve değerlendirilmesinde yapılan en son yenilikleri gözden geçirmektedir

Tribological properties of coated ASME 316L SS and comparison with a substrate

Coating is a process applied to surface of materials to have thermal insulation, hot corrosion, erosion and oxidation resistance. Due to their combination of high hardness and chemical stability thin titanium nitride and Tinalox PVD coatings have been successfully established in surface engineering. In the present study, wear and friction characteristics of TiN and Tinalox PVD coated ASME 316L stainless steel were investigated and compared with the substrate. To do this, friction and wear tests were done using Tribotester, S/N: 07-128 CSEM machine. Also, hardness variation was determined by means of CSEM Nano-Hardness Tester S/N: 4-113. It was seen that hardness was increased in TiN and Tinalox coated substrates, while friction coefficient and wear rate decreased

Friction and wear behaviour of implanted AISI 316L SS and comparison with a substrate

Ion implantation creates alterations in surface composition or morphology of solids which yield to a modification of physical and especially mechanical properties;, such as hardness and modulus of elasticity. The aim of this study is to focus on the friction and wear behaviour of N-2 and Zr implanted and TiN coated 316L stainless steel and compare with a substrate, Particularly, stainless steels were of interest, because they often display a poor tribological behaviour, which can be improved when they are hardened by incorporating N-2, TiN and Zr and forming a hardened surface zone. The present implantations were shown to improve the friction coefficient as well as the wear resistance of the stainless steel surface. (C) 2002 Elsevier Science Ltd. All rights reserved

Influence of Process Parameters on the Mechanical and Foaming Properties of PP Polymer and PP/TALC/EPDM Composites

In this study, PP and Talc/EPDM/PP composite materials are used. Foaming process is achieved by a conventional injection molding method. The influence of injection pressure and melting temperature on the average cell dimension, cell number, skin layer thickness, foam density and mechanical properties of investegated foam materials were evaluated. It is observed that cell density is increased by the increment of injection pressure. However, the values of skin layer thickness, density, cell diameter and charpy impact strength are decreased. In addition, the values of skin layer thickness, cell density, density and impact strength are increased with the increment of melting temperature

The wear behaviour investigation of sliding bearings with a designed testing machine

In this study, firstly a new wear testing machine was designed and produced in the university in order to investigate the wear behaviour of conventionally used sliding bearing alloys. Secondly, the wear tests of these bearings were performed by using this new machine. Three types of specimens' wear behaviours were tested in this constructed machine. These were tin bronzes called RB-1 and RB-7 and tin-based lead bronze called RB-4. The wear tests were performed under 10, 20 and 40 N loads with 0.5 m/s sliding speed by using ring shaped specimens. During the experiments, these specimens are put in their location in the test machine and tightened and then vertically loaded against the mile located at the center of the motor. When the experiment was started the mile turns and a force occurs to put up with the friction occurred between mile and ring interface. This force creates a moment along the mile axis and tries to turn the specimen. As a result, a deflection was observed in a plate located on the top of the machine and it is recorded by means of a transducer as a voltage (V). These data were recorded in every 10 s and stored in a data acquisition card inside the computer. The experiments were conducted for 2 h. Having finished the tests, the weight losses of the specimens were measured, the coefficient of friction values were calculated, optical and SEM investigations were performed and finally the wear behaviour of conventionally used sliding bearing alloys was characterized. (c) 2005 Elsevier Ltd. All rights reserved