An austempering study of ductile iron alloyed with copper

Austempered ductile iron (ADI) has proved to be an excellent material as it possesses attractive properties: high strength, ductility and toughness are combined with good wear resistance and machinability. These properties can be achieved upon adequate heat treatment which yields the optimum microstructure for a given chemical composition. In this paper the results of an investigation the austempering of ADI alloyed with 0.45 % Cu for a range of times and temperatures are reported. The microstructure and fracture mode developed throughout these treatments have been identified by means of light and scanning electron microscopy and X-ray diffraction analysis. It was shown that the strength, elongation and impact energy strongly depend on the amounts of bainitic ferrite and retained austenite. Based on these results, and optimal processing window was established

Polymethylmethacrylate (PMMA) welding technology

Polimetilmetakrilat (PMMA), zbog svojih karakteristika, pre svega transparentnosti i relativno male gustine, predstavlja danas vrlo atraktivan materijal u inženjerstvu. Zbog toga, istražuju se nove mogućnosti spajanja ovog materijala u cilju dobijanja kompleksnijih i većih radnih predmeta. U ovom radu su prikazane tehnike zavarivanja i spajanja, koje imaju potencijal za primenu u proizvodnji: ultrazvučno zavarivanje, toplotno spajanje, mikrotalasno zavarivanje i tačkasto zavarivanje trenjem. Takođe, prikazani su i uporedne vrednosti smicajne čvrstoće, jednog od dominantnih pokazatelja kvaliteta zavarenog spoja. Na osnovu prikazanih rezultata, najveću smicajnu čvrstoću ima tačkasto zavarivanje trenjem, sledi mikrotalasno zavarivanje, dok najmanju nosivost zavarenog spoja imaju toplotno spajanje i ultrazvučno zavarivanje. Pored toga, na osnovu specifičnosti pojedinih tehnika zavarivanja, može da se konstatuje da je tačkasto zavarivanje trenjem pogodnije za veće radne predmete, dok je veličina radnog predmeta kod mikrotalasnog zavarivanja ograničena veličinom mikrotalasne komore.Polymethylmethacrylate (PMMA) has attractive features, primarily its transparency and low density, which make it a very promising engineering material. Therefore, a novel bonding and welding techniques are being developed, to enable obtaining more complex and larger products. In this paper, perspective bonding and welding processes are presented: ultrasound welding, thermal bonding, microwave welding and friction spot welding. Furthermore, shear strengths of joints obtained by different techniques are shown. Shear strength of joints is commonly used to evaluate the quality of joints. The highest shear strength has friction spot welding, followed by microwave welding. The lowest shear strengths were obtained with thermal bonding and ultrasound welding. Specific characteristics of each joining technique determine their usefulness: friction spot welding is more suited to welding large pieces, while the work piece dimensions weldable by microwave welding is limited by microwave chamber size

Microstructure and fracture mode of unalloyed dual-phase austempered ductile iron

Dual-phase ADI material microstructure consists of different amounts and morphologies of ausferrite and free ferrite, obtained by subjecting ductile iron to specific heat treatment. Its strength is lower compared to comparable ADI materials but exhibits a higher ductility, the major disadvantage of ADI. In the current study, an unalloyed ductile iron was intercritical austenitized in two-phase regions (??+??) at four temperatures from 840 to 780 ??C for 2 h and austempered at 400 ??C for 1 h to obtain dual-phase ADI with different percentages of free ferrite and ausferrite. Light and scanning electron microscopy was performed for the metallographic and fracture studies, respectively. Microscopy results were correlated to tensile testing results. The results indicated that, as the amount of ausferrite present in the matrix increases, higher values of strength and lower ductility are obtained. The fracture surfaces of dual-phase ADI microstructures with 22.8% of ausferrite in their matrix have regions of quasi-cleavage fracture around last-to-freeze zones, related to the presence of ausferrite in those areas. The specimens with the highest values of ausferrite of 86.8% among the dual-phase microstructure have a dominant quasi-cleavage type of fracture

Ballistic Behaviour of Austempered Compacted Graphite Iron Perforated Plates

In this study, the performance of austempered compacted graphite iron was evaluated to find its suitability as perforated plates used in add-on armour. Perforated compacted graphite plates were subjected to austenitisation at 900 °C for 2 h followed by austempering at 275 and 400 °C for 1 h. The basic plate was fixed at 400 mm away from the perforated plate and armour and then piercing incendiary projectile was shot from a distance of 100 m. It was observed that both 7 mm and 9 mm perforated plates austempered at lower temperature of 275 °C producing higher hardness and lower ductility were effective in fracturing the penetrating core, thereby significantly decreasing the chances of penetrating the basic plate

Ballistic Behaviour of Austempered Compacted Graphite Iron Perforated Plates

In this study, the performance of austempered compacted graphite iron was evaluated to find its suitability as perforated plates used in add-on armour. Perforated compacted graphite plates were subjected to austenitisation at 900 degrees C for 2 h followed by austempering at 275 and 400 degrees C for 1 h. The basic plate was fixed at 400 mm away from the perforated plate and armour and then piercing incendiary projectile was shot from a distance of 100 m. It was observed that both 7 mm and 9 mm perforated plates austempered at lower temperature of 275 degrees C producing higher hardness and lower ductility were effective in fracturing the penetrating core, thereby significantly decreasing the chances of penetrating the basic plate

The standard processing window of alloyed ADI materials

In present paper the effect of austempering conditions and alloying elements on the microstructure, mechanical properties and processing window of Cu and Cu + Ni alloyed austempered ductile irons has been studied. A new concept of "standard" processing window was suggested as an alternative to the well-known "microstructure" processing window. This concept is based on the ability to achieve mechanical properties required by different standards, namely ASTM, ISO and EN. The results obtained show that alloying with Cu + Ni produced ductile grades of ADI, while alloying with Cu grades of higher strength. The standard processing window depends on the austempering parameters and alloying elements, as well as standard used. The ISO and EN standards give a larger standard processing window compared to the ASTM. It was also shown, that from the engineering point of view, determination of a standard processing window gives great advantage compared to the microstructure processing window where special methods and procedures have to be used

Transition temperature and fracture mode of as-castand austempered ductile iron

The ductile to brittle transition temperature is a very important criterion that is used for selection of materials in some applications, especially in low-temperature conditions. For that reason, in this paper transition temperature of as-cast and austempered copper and copper-nickel alloyed ductile iron (DI) in the temperature interval from -196 to +150 degrees C have been investigated. The microstructures of DIs and ADIs were examined by light microscope, whereas the fractured surfaces were observed by scanning electron microscope. The ADI materials have higher impact energies compared with DIs in an as-cast condition. In addition, the transition curves for ADIs are shifted towards lower temperatures. The fracture mode of Dls is influenced by a dominantly pearlitic matrix, exhibiting mostly brittle fracture through all temperatures of testing. By contrast, with decrease of temperature, the fracture mode for ADI materials changes gradually from fully ductile to fully brittle

Wire fence as applique armour

In this paper, the behaviour of wire fence was investigated for potential as applique armour. The wire fence used was made from commercial high-strength patented wire and the supporting frames were made of mild steel L-profiles. Both patented wire and L-profiles are of-the-shelf materials. The fence was tested by firing 12.7 min M8 API ammunition at four applique armour models: two of these models use a parallel wire arrangement, with one mounted at a 90 degrees angle from the incoming projectile and the other at 70 degrees; and two of these models use a zig-zag wire arrangement, one mounted at a firm 90 degrees, angle and the other is left in a hanging arrangement. Fence damage was correlated with RHA basic plate damage, on both the face and back. Wire fence has considerable potential as an improvised applique armour, except if the projectile impacts near the center of the wire or near the center between two wires. The latter case was successfully overcome by placing the armour model at an angle and by using a zig-zag wire arrangement. The lowest basic RHA plate damage level was found using the hanging armour model. However, from the point of view of ease of attachment, the most convenient was found to be the armour model with the zig-zag wire arrangement fixed at 90 degrees angle from the incoming projectile. SEM fracto graphy revealed that the fracture surface was predominantly ductile, with dimples filled with debris from the incendiary effect of the projectile

The austempering study of alloyed ductile iron

Austempered ductile iron (ADI) proved to be an excellent material as it possesses attractive properties: high strength, ductility and toughness are combined with good wear resistance and machinability. These properties can be achieved upon adequate heat treatment which yields optimum microstructure for a given chemical composition. In this paper an investigation has been conducted on ADI alloyed with 0.45%Cu and austempered in a range of times and temperatures. The microstructure and fracture mode developed throughout these treatments have been identified by means of light and scanning electron microscopy and X-ray diffraction analysis. It was shown that strength, elongation and impact energy strongly depend on amounts of bainitic ferrite and retained austenite. Based on these results an optimal processing window has been established

Austempering Kinetics of Cu-Ni Alloyed Austempered Ductile Iron

The aim of the paper was to investigate the effect of austempering parameters (time and temperature) on the microstructure and mechanical properties of ADI alloyed with 1.5% Cu and 1.6% Ni (in wt.%) in order to establish the optimal processing window. It was shown that the strength, elongation and impact energy strongly depend on the amounts of ausferritic ferrite and retained austenite. A processing window was established according to the results of the kinetics of the isothermal transformation. The results show that the processing window for ADI alloyed with Cu and Ni at 350 degrees C was relatively wide, while the processing window for the isothermal transformation at 400 degrees C becomes narrower and shifted to the left. The processing window of ADI austempered at 300 degrees C is also narrower, but shifted to the right towards the longer times compared to the processing window of ADI austempered at 350 degrees C