| 1. |
- Ahmadpour, A., et al.
(författare)
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Effect of stirring on behaviour of double oxide film defects in A356 aluminium melt
- 2014
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Ingår i: International Journal of Cast Metals Research. - : Taylor & Francis. - 1364-0461 .- 1743-1336. ; 27:4, s. 221-229
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Tidskriftsartikel (refereegranskat)abstract
- The effect of stirring of melt on the behaviour of double oxide film (bifilm) defects in A356 melt was investigated using a reduced pressure test (RPT) technique. The melt was poured from a height into a crucible to introduce bifilms into the melt. The melt was then either remained stagnant or mechanically stirred, and RPT samples were taken from the melt at 8 min intervals. The RPT samples were then characterised by determination of their porosity parameters and examination of the internal surfaces of the pores using a scanning electron microscope. The results showed that stirring of the melt facilitated the diffusion of H in the melt into the atmosphere of the defects and hence accelerated the removal of the defects from the melt by floatation. This effect was attributed to the increase in the stress induced to the defects, which increased the rate of formation of cracks on their layers.
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| 2. |
- Alirezaei, Mohammadamin, et al.
(författare)
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Microstructure evolution in cast and equilibrium heat-treated CuZn30-(Si) alloys
- 2016
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Ingår i: International Journal of Cast Metals Research. - : Informa UK Limited. - 1364-0461 .- 1743-1336. ; 29:4, s. 222-227
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Tidskriftsartikel (refereegranskat)abstract
- The main object of this work was to investigate the effect of Si addition and heat treatment on the microstructure of CuZn30 alloy. The alloys were prepared by casting and then the chemical composition, microstructure and phases were determined by optical and scanning electron microscope and XRD analysis. The resulting microstructures contained two phases, alpha and beta', with volume fraction depending on silicon content. Increments of Si content led to the formation of a Widmanstatten structure. It was also found that the silicon dissolved completely in alpha + beta phases and the lattice parameters of both alpha- and beta'-phases increased as the Si content increased. Hardness tests showed that hardness of both the as-cast and heat-treated samples increased as the Si content increased, and a significant increment of hardness in heat-treated alloy was due to the formation of a martensite phase.
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| 3. |
- Amirinejhad, S., et al.
(författare)
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Study of double oxide film defect behaviour in liquid Al-Mg alloys
- 2013
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Ingår i: International Journal of Cast Metals Research. - : Taylor & Francis. - 1364-0461 .- 1743-1336. ; 26:6, s. 330-338
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Tidskriftsartikel (refereegranskat)abstract
- The change in the composition of oxide layers and the possibility of the formation of bonding between the layers of a double oxide film defect when held in Al melts containing 0.7, 1 and 2 wt-%Mg were investigated. The defect was modelled by maintaining two aluminium oxide layers in contact with one another in the melt at 1023 K for times between 5 s and 50 h. Any changes in the composition and morphology of these layers were studied by SEM and energy dispersive X-ray. The results showed that in all the alloys, the initial Al2O3 layer first transformed to MgAl2O4 and then to MgO. These transformations caused the two layers to bond together gradually. The results confirmed that, in all the Al alloys containing 0.3-4.5 wt-%Mg, oxide films have the chance to heal if held in the liquid metal for a long enough period of time.
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| 4. |
- Bogdanoff, Toni, et al.
(författare)
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A simple procedure to assess the Complete Melt Quality in aluminium castings : implementation in a die-casting and a rheo-casting
- 2024
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Ingår i: International Journal of Cast Metals Research. - : Taylor & Francis. - 1364-0461 .- 1743-1336. ; 37:1, s. 71-79
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Tidskriftsartikel (refereegranskat)abstract
- A new simple approach was developed to assess the Complete Melt Quality of aluminium cast alloys throughout the production line. The approach relies on the concurrent use of reduced pressure tests (RPT) and tensile tests at each station in the production line when the melt is transferred and/or processed. These tests can be used to determine the source of melt-related problems in the production line. Two case studies from the procedure of both an aluminium die-casting and a rheo-casting plant showed that melts were significantly damaged in the tower furnace and got progressively more damaged through the production line proven by the RPT, tensile test, and fracture surface analysis results.
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| 5. |
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| 6. |
- Cao, Haiping, et al.
(författare)
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Characteristics of microstructure and banded defects in die-cast AM50 magnesium components
- 2005
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Ingår i: International Journal of Cast Metals Research. - : Maney Publishing. - 1364-0461 .- 1743-1336. ; 18:6, s. 377-384
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Tidskriftsartikel (refereegranskat)abstract
- It has become more and more common for companies to move part of their production to low cost countries and/or closer to important markets. However, quite often the product development is not moved. The result is an increased distance between product development and production. The interface between the two departments is important to lead time, cost and quality and therefore the cooperation must work smoothly. To achieve this, most literature recommends early and tight cooperation. However this can be complicated by expensive and time consuming travels and/or usage of less rich communication such as emails and phone calls. It is difficult to make the transition in general from product development to production and the possible problems increase with the distance. The PD-P interface consists of several components and how a problem in one component is affected by problems in other components is not explicitly discussed in literature. The purpose in this paper is to explore if there are such connections i.e. connections between an observable problem and other components in the PD-P interface in a geographically dispersed setting. The paper does so by merging the distributed work literature and the PD-P interface literature. The analysis is based on four PD-P interface components; technological, organizational, scope and task. The analysis indicates that observable problems as e.g. low frequency of communication can be the symptom of one or a combination of problems. Connections between the components in the PD-P interface are exemplified in a geographically dispersed setting. Furthermore the underlying causes to the problems connected to the geographically dispersed setting in the PD-P interface are elucidated. In the case of low frequency of communication, it could be the technical system hindering communication and the different time zones disrupt it even more. Hence one symptom could be caused by different underlying problems. Each problem needs to be broken down to find the cause and the solution could be found in any of the four interface components. The results indicate that the actual distance is not the biggest problem but uncertainties (e.g. new collaborations) and differences (culture and work methods) which increase lead time. We have also seen that single underling problems can cause problem in several of the PD-P interface components. This indicates that if these underlying problems can be solved the project results can be vastly improved. For example, trust issues occur in the scope component (affects the willingness to share information) and in the organizational interface component (both competence trust and goodwill trust affects involvement and commitment to the project). Consequently, if problems like this can be solved many other problems will become minor problems and project objectives will be more likely to be obtained. However trust is difficult to achieve with a geographical distance between product development and production. The analysis also indicates that due to the distance more attention is paid to the PD-P interface, e.g. more experienced team members are appointed. This can be contributing to a smoother PD-P interface than expected.
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| 7. |
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| 8. |
- Diaconu, Lucian Vasile, et al.
(författare)
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Influence of molybdenum alloying on thermomechanical fatigue life of compacted graphite irons
- 2012
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Ingår i: International Journal of Cast Metals Research. - : Maney Publishing. - 1364-0461 .- 1743-1336. ; 25:5, s. 277-286
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Tidskriftsartikel (refereegranskat)abstract
- In this study four compacted graphite irons (CGIs) and one grey cast iron (FGI) were produced and tested in the laboratory. The molybdenum content of the four CGI grades was varied between 0 and 1·01 wt-%. The purpose of the investigations was to examine the effect of the different molybdenum contents of the CGI on the thermomechanical fatigue (TMF) behaviour. The TMF tests were performed by cycling a constrained specimen between 110 and 600°C. For every material three tests were performed on specimens machined from a Ø20 mm cylinder. Other tests were performed on specimens machined from Ø55 mm and Ø85 mm cylinders respectively. The tests showed that additions of molybdenum improved the fatigue resistance of CGI. It was observed that additions of molybdenum refined the pearlite and that the specimens with a finer metallic matrix had a higher TMF resistance.
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| 9. |
- Diaconu, Lucian Vasile, et al.
(författare)
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Stress relaxation of compacted graphite iron alloyed with molybdenum
- 2013
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Ingår i: International Journal of Cast Metals Research. - : Taylor & Francis. - 1364-0461 .- 1743-1336. ; 26:1, s. 51-57
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Tidskriftsartikel (refereegranskat)abstract
- In a previous study, the thermomechanical fatigue resistance of four compacted graphite irons (CGIs) and one grey cast iron was investigated. The molybdenum content of the four CGIs varied between 0 and 1.01 wt-%. It was observed that during thermal cycling, the maximum value of the compressive stress continuously decreased while the value of the maximum tensile stress continuously increased. The continuous decrease in compressive stresses showed that stress relaxation occurs at elevated temperatures during thermal cycling. The goal of the present investigation was to investigate the phenomenon of stress relaxation at elevated temperatures. The tests were performed at 350 and 600uC respectively. The results of the stress relaxation tests performed at 600uC showed the same trend observed at thermomechanical fatigue testing. The tests showed that additions of molybdenum improved the fatigue resistance of CGI by lowering the stress relaxation rate.
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| 10. |
- Diószegi, Attila, 1962-, et al.
(författare)
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Austenite dendrite morphology in lamellar graphite iron
- 2015
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Ingår i: International Journal of Cast Metals Research. - : Maney Publishing. - 1364-0461 .- 1743-1336. ; 28:5, s. 310-317
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Tidskriftsartikel (refereegranskat)abstract
- Primary austenite has been underestimated in general when the theories of nucleation, solidification, microstructure formation and mechanical properties were established for cast iron and particularly for lamellar cast iron. The present work aims to investigate the primary austenite morphology of as cast samples of a hypoeutectic lamellar cast iron produced with different cooling rates. Morphological parameters as the area fraction primary austenite, the secondary dendrite arm spacing, the dendrite envelope surface, the coarseness of the primary dendrite expressed as the relation between the volume of the dendrite and its envelope surface and the coarseness of the interdendritic space also known as the hydraulic diameter are measured. Furthermore, the role of the size of the investigation area is revealed to be sequential investigation. A strong relation between all measured morphological parameters and the solidification time has been established, except the volume fraction of primary austenite, which is constant for all cooling conditions.
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