Effetto di affinante e modificante sulla microstruttura delle leghe Al-Si da colata = Effect of refining and modification on the microstructure of Al-Si casting alloys

La necessità di ridurre le emissioni di CO2 ha spinto i produttori di veicoli verso l’adozione di materiali in grado di garantire una riduzione del peso quanto più possibile consistente. Per questa ragione, oltre che per le buone proprietà meccaniche specifiche, le leghe alluminio-silicio trovano vasta applicazione nel settore dell’autoveicolo. Sebbene le leghe Al-Si siano leghe note e oggetto di numerosissimi studi, un ulteriore passo in avanti può coinvolgere la valutazione degli effetti degli additivi modificanti ed affinanti sulla microstruttura della lega e sulla forma delle fasi intermetalliche. In questo lavoro, dei getti in lega EN AC 45300 (AlSi5Cu1Mg), verranno analizzati nello stato as-cast e in seguito a trattamento termico T6, con e senza l’adozione di agenti affinanti e modificanti, con l’obiettivo di studiare le evoluzioni che avvengono nelle microstrutture in termini di morfologia delle fasi intermetalliche

Focus on Carbide-Tipped Circular Saws when Cutting Stainless Steel and Special Alloys

Circular saw blades are used exclusively for cut-off work, ranging from small manual feed operations, up to very large power fed saws commonly used for sectioning stock as it comes from a rolling mill or other manufacturing processes for long products. The teeth profile, as well as the tooth configuration are of fundamental importance for the blade performances; through a combination of blade rigidity and grinding wheel condition a good quality surface finish is attained for tools of commercial standard. The materials used for the production of circular saw blades are ranging from high speed steel to cemented carbides. In particular, cemented carbides, being characterized by high hardness and strength, are used in applications where materials with high wear resistance and toughness are required. The main constituents of cemented carbides are tungsten carbide and cobalt. Tungsten carbide imparts the alloys the necessary strength and wear resistance, whereas cobalt contributes to the toughness and ductility of the alloys. The WC-Co alloys are tailored for specific applications by the proper choice of tungsten carbide grain size and the cobalt content. The grain size of the tungsten carbide in WC-Co varies from about 40 μm to around 0.3 μm, the cobalt content from 3 to 30 wt%. The coarse grained hard metals are mainly used in mining applications, the smallest grain size being about 3 μm and the minimum cobalt content 6 wt%. The grain size of tungsten carbide in the metal cutting industry, as well as for universal applications lies in the range of 1-2 μm. However, with the advent of near net shape manufacturing and thin walled components, the use of submicron carbide is growing, since their high compressive strength and abrasive wear resistance can be used to produce tools with a sharp cutting edge and a large positive rake angle. In this paper, a general overview on the actual trends in the choice of the best material when cutting special alloys will be presented and discussed. Based on the recent and past literature some examples of their up-to-date application, such as circular saws used to cut stainless steels and some high strength alloys, are talk ove

PAINT CHARACTERIZATION TO IMPROVE THE MOULD DURABILITY IN THE ALUMINUM GRAVITY CASTING

The collection of the conference proceedings presented during the 11th world congress Aluminium Two Thousand, Treviso, Italy. La raccolta delle relazioni presentate durante l'11° congresso mondiale Aluminium Two Thousand, 9-13 Aprile 2019, Treviso, Ital

Effects of Casting-Additives on the Microstructure Evolution of Hypoeutectic Aluminium-Silicon Alloys

Since the industries are called to produce environmentally friendly products, the research is moving toward new improved materials. In this panorama, aluminium alloys find applications for a large range of products. In the automotive, as well as in the aerospace, sector, aluminium alloys are largely adopted, thanks to their high specific properties and their light weight. Moreover, common casting techniques permit us to realize complex high-quality components. These components may be realized by using casting techniques adopting casting-additives, such as modifiers or refiners. In this work, the effect of refining and modification was studied in terms of microstructural evolution of the intermetallic phases in two aluminium-silicon alloys (EN AC 45300 and EN AC 43500). Microstructures were analyzed through micro-hardness measures, and we found a reduction in the standard deviation of the hardness with the addition of additives. Furthermore, secondary dendrites arms spacings (SDAS) were measured, evidencing a decrease in SDAS by adding casting additives. A strong correlation was found between the adding of additives and the possibility of containing the size of the silicon and of all the intermetallic phases opening up to the possibility of tailoring the microstructure

The Local Squeeze Technology for Challenging Aluminium HPDC Automotive Components

A key issue in producing high-quality aluminium automotive components by the High-Pressure Die Casting process (HPDC) is minimizing the defects. For the HPDC technology, the wall thickness of components needs to be monitored because it dramatically affects the grain size and porosity appearance. In this work, local squeeze technology is used in aluminium high-pressure die casting. The aim is to optimize quality in thick sections of complex geometries, where designers cannot modify components' features and the casting process cannot solve shrinkage porosities with the state-of-the-art process control, like intensification pressure or cooling management. The present paper relates to a study of the squeeze pin effect on HPDC aluminium parts, where material homogeneity for leak prevention is a must. Both product and process development for reliable industrialization of the local squeeze technology will be covered, from casting virtual simulation to the metallurgical analysis of the affected area. The affected area was analyzed by means of to understand the local squeeze effect on microstructures

About Residual Stress State of Castings: The Case of HPDC Parts and Possible Advantages through Semi-Solid Processes

Nowadays, one of the most crucial focus in the aluminium-foundry sector is the production of high-quality castings. Mainly, High-Pressure Die Casting (HPDC) is broadly adopted, since by this process it is possible to realize aluminium castings with thin walls and high specific mechanical properties. On the other hand, this casting process may cause tensile states into the castings, namely residual stresses. Residual stresses may strongly affect the life of the product causing premature failure of the casting. Various methods can assess these tensile states, but the non-destructive X-Ray method is the most commonly adopted. Namely, in this work, the residual stress analysis has been performed through Sinto-Pulstec µ-X360s. Detailed measurements have been done on powertrain components realized in aluminium alloy EN AC 46000 through HPDC processes to understand and prevent dangerous residual stress state into the aluminium castings. Furthermore, a comparison with stresses induced by Rheocasting processes is underway. In fact, it is well known that Semi-Solid metal forming combines the advantages of casting and forging, solving safety and environmental problems and possibly even the residual stress state can be positively affected