scholarly journals Syntactic Iron Foams’ Properties Tailored by Means of Case Hardening via Carburizing or Carbonitriding

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4358
Author(s):  
Jörg Weise ◽  
Dirk Lehmhus ◽  
Jaqueline Sandfuchs ◽  
Matthias Steinbacher ◽  
Rainer Fechte-Heinen ◽  
...  

Metal foam inserts are known for their high potential for weight and vibration reduction in composite gear wheels. However, most metal foams do not meet the strength requirements mandatory for the transfer of sufficiently high levels of torque by the gears. Syntactic iron and steel foams offer higher strength levels than conventional two-phase metal foams, thus making them optimum candidates for such inserts. The present study investigates to what extent surface hardening treatments commonly applied to gear wheels can improve the mechanical properties of iron-based syntactic foams. Experiments performed thus focus on case hardening treatments based on carburizing and carbonitriding, with subsequent quenching and tempering to achieve surface hardening effects. Production of samples relied on the powder metallurgical metal injection molding (MIM) process. Syntactic iron foams containing 10 wt.% of S60HS hollow glass microspheres were compared to reference materials without such filler. Following heat treatments, the samples’ microstructure was evaluated metallographically; mechanical properties were determined via hardness measurements on reference samples and 4-point bending tests, on both reference and syntactic foam materials. The data obtained show that case hardening can indeed improve the mechanical performance of syntactic iron foams by inducing the formation of a hardened surface layer. Moreover, the investigation indicates that the respective thermo-chemical treatments can be applied to composite gear wheels in exactly the same way as to monolithic ones. In the surface region modified by the treatment, martensitic microstructures were observed, and as consequence, the bending limits of syntactic foam samples were increased by a factor of three.

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 73
Author(s):  
Tobias Bubmann ◽  
Andreas Seidel ◽  
Holger Ruckdäschel ◽  
Volker Altstädt

Reactive compounding of terminally phenolic OH-functionalized polycarbonate (PC) with epoxy-functionalized polymethylmethacrylate (PMMA) prepared by copolymerization with glycidyl methacrylate was investigated. It was spectroscopically demonstrated that a PC/PMMA copolymer was formed during the melt reaction of the functional groups. Zirconium acetylacetonate could catalytically accelerate this reaction. Correlations of the phenomenological (optical and mechanical) properties with the molecular level and mesoscopic (morphological) structure were discussed. By the investigated reactive compounding process, transparent PC/PMMA blends with two-phase morphologies were obtained in a continuous twin-screw extruder, which, for the first time, combined the high transmission of visible light with excellent mechanical performance (e.g., synergistically improved tensile and flexural strength and high scratch resistance). The transparency strongly depended on (a) the degree of functionalization in both PC and PMMA, (b) the presence of the catalyst, and (c) the residence time of the compounding process. The in-situ-formed PC/PMMA copolymer influenced the observed macroscopic properties by (a) a decrease in the interphase tension, leading to improved and stabilized phase dispersion, (b) the formation of a continuous gradient of the polymer composition and thus of the optical refractive indices in a diffuse mesoscopic interphase layer separating the PC and PMMA phases, and (c) an increase in the phase adhesion between PC and PMMA due to mechanical polymer chain entanglement in this interphase.


2005 ◽  
Vol 881 ◽  
Author(s):  
B. Krevet ◽  
M. Kohl

AbstractIn this work, we present simulations of the thermo-magneto-mechanical performance of a ferromagnetic SMA microactuator in the inhomogeneous field of a CoSm permanent magnet and compare it with experimental results. For the simulations, a combination of different finite element (FEM) programs is used allowing the coupling of electrical, thermal, magnetic and mechanical properties. The field of a permanent magnet is calculated along the trajectory of the microactuator, from which the magnetic forces Fmag and their gradients are derived. Shape memory forces FSME are calculated based on a two-phase macromodel. Both forces, Fmag and FSME, determine the quasi-static behavior of a NiMnGa microscanner, which has been proposed recently.


2015 ◽  
Vol 816 ◽  
pp. 682-687
Author(s):  
Cong Bo Li ◽  
Wei Wei Chen ◽  
Lu Wang

Amorphous Al-Cu-Ti metal foams with the porosity of 65% were prepared by spark plasma sintering with both the diameter and height of 10 mm. The SPS process was carried out under the pressure, the dwell time and the temperatures of 300 MPa, 5min and 623-673K, respectively. The microstructure and mechanical behavior of the amorphous Al-Cu-Ti metal foams were investigated. The results showed that sintering at high temperatures improved the crystallinity and adhesion between particles. The intermetallic compounds, i.e. Al-Ti, Al-Cu and Al-Cu-Ti were identified from the XRD patterns. It was found that weak adhesion and irregular shape of NaCl might reduce the mechanical properties. The highest strength of amorphous Al-based metal foam sintered at 653K, 300MPa was 7.97MPa.


2013 ◽  
Vol 586 ◽  
pp. 120-124 ◽  
Author(s):  
Tomáš Fíla ◽  
Daniel Kytýř ◽  
Petr Koudelka ◽  
Tomáš Doktor ◽  
Petr Zlámal ◽  
...  

This paper is focused on determination of micro-mechanical material properties of aluminium metal foam at level of single cell wall. For the purpose of homogenization, complex and heterogenous inner structure of metal foams requires deep understanding of its deformation mechanisms and local mechanical properties. Therefore, a series of micro-scale bending tests of specimens prepared from foam's cells wall were performed. Initially, a technique of specimen preparation was developed. Dimensions and geometry of the specimens were inspected using scanning electron microscopy (SEM). Custom-designed three-point bending device suitable for testing at micro-scale was used for loading. Thin pure aluminium metal sheets were used for calibration of the described method. Six single cell wall specimens were tested. It can be concluded that the developed specimen preparation technique and loading method are suitable to determine local mechanical properties of thin walled metal foams.


2021 ◽  
Vol 4 (2) ◽  
pp. 93-96
Author(s):  
Domonkos Balázs Kincses ◽  
Alexandra Kemény ◽  
Borbála Leveles ◽  
Dóra Károly

Abstract Composite metal foams are hybrid structures with the main advantages of high specific strength and mechanical energy absorption associated with low density. In the course of our research, we successfully manufactured functional metal foams of EN AC-44200 matrix filled with lightweight expanded clay aggregate particles (LECAPs) in EN AW-6060 alloy tubes with a diameter of 50 mm and a wall thickness of 5 mm. Manufacturing was performed by low-pressure infiltration directly into the aluminium tube. Six different types of samples were examined: metal matrix syntactic foam, in-situ metal foam, ex-situ metal foam, and their heat-treated pairs. In the compression tests, the heat treatment provided a visible improvement in the results of the ex-situ metal foams.


2019 ◽  
Vol 70 (10) ◽  
pp. 3469-3472

Weldability involves two aspects: welding behavior of components and safety in operation. The two aspects will be reduced to the mechanical characteristics of the elements and to the chemical composition. In the case of steel reinforcing rebar’s, it is reduces to the percentage of Cech(carbon equivalent) and to the mechanical characteristics: the yielding limit, the ultimate limit, and the elongations which after that represent the ductility class in which the re-bars is framed. The paper will present some types of steel reinforcing rebar’s with its mechanical characteristics and the welding behavior of those elements. In the current work, process-related behavior of welded reinforcement, joint local and global mechanical properties, and their correlation with behavior of normal reinforcement and also the mechanical performance resulted in this type of joints. Keywords: welding behavior, ultimate limit, reinforcing rebar’s


Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1124
Author(s):  
Zhifang Liang ◽  
Hongwu Wu ◽  
Ruipu Liu ◽  
Caiquan Wu

Green biodegradable plastics have come into focus as an alternative to restricted plastic products. In this paper, continuous long sisal fiber (SF)/polylactic acid (PLA) premixes were prepared by an extrusion-rolling blending process, and then unidirectional continuous long sisal fiber-reinforced PLA composites (LSFCs) were prepared by compression molding to explore the effect of long fiber on the mechanical properties of sisal fiber-reinforced composites. As a comparison, random short sisal fiber-reinforced PLA composites (SSFCs) were prepared by open milling and molding. The experimental results show that continuous long sisal fiber/PLA premixes could be successfully obtained from this pre-blending process. It was found that the presence of long sisal fibers could greatly improve the tensile strength of LSFC material along the fiber extension direction and slightly increase its tensile elongation. Continuous long fibers in LSFCs could greatly participate in supporting the load applied to the composite material. However, when comparing the mechanical properties of the two composite materials, the poor compatibility between the fiber and the matrix made fiber’s reinforcement effect not well reflected in SSFCs. Similarly, the flexural performance and impact performance of LSFCs had been improved considerably versus SSFCs.


Coatings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 41
Author(s):  
Yin-Yu Chang ◽  
Cheng-Hsi Chung

Multi-element material coating systems have received much attention for improving the mechanical performance in industry. However, they are still focused on ternary systems and seldom beyond quaternary ones. High entropy alloy (HEA) bulk material and thin films are systems that are each comprised of at least five principal metal elements in equally matched proportions, and some of them are found possessing much higher strength than traditional alloys. In this study, CrVTiNbZr high entropy alloy and nitrogen contained CrVTiNbZr(N) nitride coatings were synthesized using high ionization cathodic-arc deposition. A chromium-vanadium alloy target, a titanium-niobium alloy target and a pure zirconium target were used for the deposition. By controlling the nitrogen content and cathode current, the CrNbTiVZr(N) coating with gradient or multilayered composition control possessed different microstructures and mechanical properties. The effect of the nitrogen content on the chemical composition, microstructure and mechanical properties of the CrVTiNbZr(N) coatings was investigated. Compact columnar microstructure was obtained for the synthesized CrVTiNbZr(N) coatings. The CrVTiNbZrN coating (HEAN-N165), which was deposited with nitrogen flow rate of 165 standard cubic centimeters per minute (sccm), exhibited slightly blurred columnar and multilayered structures containing CrVN, TiNbN and ZrN. The design of multilayered CrVTiNbZrN coatings showed good adhesion strength. Improvement of adhesion strength was obtained with composition-gradient interlayers. The CrVTiNbZrN coating with nitrogen content higher than 50 at.% possessed the highest hardness (25.2 GPa) and the resistance to plastic deformation H3/E*2 (0.2 GPa) value, and therefore the lowest wear rate was obtained because of high abrasion wear resistance.


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