Papers by Author: Mario Rosso

Abstract: The Al-alloy die casting die is a sector where the operating environment imposes a very severe aggression to hot working tools. Steel grades for such application, techniques for their surface modification and specifically conceived lubricants are continuously improved so as to limit Al soldering. Within this scenario the interaction between lubricant and die surface and the effect of finishing levels of such surface is poorly studied. This paper deals with a study of the influence of dies surface roughness on the working behavior of a die casting lubricant and on surface damages of a tool steel grade. Tool steel samples were prepared for the research and two different levels of surface roughness (as polished and as finely sand blasted) were investigated. Apart from the base characterization of steels and surface, two specific test rigs were used to study the lubricant-tool steel surface-Al alloy interactions. One of test rig was devoted to study the coupling principles of tool die surface-lubricant, while the other test rig was used to perform a cyclic immersion test in molten Al-alloy. The derived data were compared to the experimental investigation of cracks and craters as provided by cycling with a correlation with the surface finishing level of samples.

Abstract: Functionally graded materials (FGM) are used for components with specific characteristics required by the considered area of application. In this research, functionally graded material is obtained with sequential casting process of two different aluminum alloys. They are poured into the mould, aiming to obtain within the same component high thermal resistance and mechanical strength on one side and ductility and elongation on the other side.The new casting has high potential, especially in the production of automotive components, e.g., pistons. Usually, piston alloys are eutectic Al-Si alloys, with high percentage of other alloying elements which increases the thermal resistance of the material. However, this high concentration of alloying elements leads to a considerable reduction of the material’s elongation that is not always tolerable. The low ductility can be an issue for the inferior part of the piston that is more subjected to fatigue stress. To increase the elongation, in addition to the alloy used for the manufacturing, a hypoeutectic Al-Si alloy is considered in the sequential casting of the FGM, that in turn gives rise to a superior ductility in the component.The purpose of this research is the optimization of the manufacturing process parameters of a functionally graded material to be used for the production of a more performing element. In particular, the produced piston shows a superior resistance at high temperatures in the area which it is in contact with the gas combustion and, simultaneously exhibits a superior fatigue life on its lateral part.

Abstract: The present chapter reports a short history and a state-of-the art of semi-solid techniques, with particular emphasis to the role of the liquid-solid fraction, being the rheological behaviour of the semi-solid slurry crucial and fundamental. The general description, with the related theoretical fundaments, is based on the data available in the recent and the past literature and finally it is integrated with some experimental results of the research carried out by the authors.

Abstract: Cost-effective, modified, self-hardening Al-based alloy is proposed for automotive and aircraft industries. AlZn10Si8Mg is produced by permanent mould casting technique, and the obtained material is re-melted to refine and modify its microstructure and to develop a mechanically more efficient alloy. Ti as grain refiner, in form of TiB, and modifier, in forms of AlSr, were added to the basic alloy composition. Microstructural analysis and impact toughness evaluation were performed at room temperature and up to 180°C. The results obtained confirm that the proposed alloy reveal good properties in the considered temperature range, and demonstrate their applicability for structural components development in the aforementioned areas and in a wide range of temperature.

Abstract: During the last decades under the enthusiastic and competent guidance of Mr Chiarmetta SSM processes attained in Italy at Stampal Spa (Torino) an unquestionable high level of industrial development with the production of large numbers of high performance automotive parts, like variety of suspension support, engine suspension mounts, steering knuckle, front suspension wheel, arm and rear axle. Among the most highlighted findings SSM processes demonstrated their capability to reduce the existing gap between casting and forging, moreover during such a processes there are the opportunity to better control the defect level.Purpose of this paper is to highlight the research work and the SSM industrial production attained and developed by Mr G.L. Chiarmetta, as well as to give an overview concerning some alternative methods for the production of enhanced performance light alloys components for critical industrial applications and to present an analysis of a new rheocasting process suitable for the manufacturing of high performance industrial components.

Abstract: The study aims obtaining materials with a high and constant friction coefficient, a high durability and thermal stability that is associated to a lower wear rate, to the absence of noise during braking and to good self-brazing capacity. Cu and Fe-based friction materials have been sintered and the influence of the loading graphite and ceramic filler powders on the friction and wear properties were investigated. Optimization of the composition and of the sintering method were performed targeting to obtain higher tribological properties, compared to the actually produced polymer matrix materials used for the same purpose, in a cost-effective way. The samples, sintered at different temperatures were observed by optical and scanning electron microscopies, while the tribological behavior was investigated by the evaluation of the friction coefficient and wear rate. The worn surfaces of the wear samples were analyzed: principally an abrasive wear was revealed, explained mostly by the presence of ceramic particles. Moreover, due to the high pressure applied combined to an increased temperature, the presence of adhesive wear was detected. The experimentally achieved results show that using a Cu based material with a moderate graphite and ceramic content is a promising material for the considered application. Optimization of the noise reduction during braking is undergoing.

Abstract: The WE43 is a Mg-Y-Nd alloy that presents good mechanical properties and an high creep resistance. For these reasons currently is widely used in the aerospace and automotive industries. The setting of the right thermal heat treatment parameters plays a crucial role in determine the microstructure and consequently the mechanical properties of the alloy. With this in mind, the main goal of this work has been that to identify the optimal parameters to achieve a high impact resistance and at the same time, the most suitable choice, to reach also an important cost-saving solution, which is extremely important especially from the industrial point of view.

Abstract: Conformal metasurfaces are even more diffused in different fields from optics to electromagnetics. Advanced applications, as making object invisible to incident fields also known as cloaking, require high precision realizations, since the resonant answer of the system is very sensitive to geometry details. Practical realizations are provocative, since material characteristics and mechanical restrictions should also be considered. Multi- and inter-disciplinary interactions are mandatory to overcome such technological challenges. Due to its excellent esthetic characteristics, good physical and mechanical properties, Aluminium is widely used for deposition on different substrates: physical and chemical vapor depositions are very suitable for micro-metallization process and for the realization of multilayered structures. This paper presents some results about the behavior of a cylindrical-shape system realized by Al films deposition on flexible, polymeric organosilicon substrate.

Abstract: 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 hardmetals 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 invited 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 over.

Abstract: This paper concerns with the optimisation of the innovative rheocasting process to produce a new generation of brake callipers, characterised by very high reliability and strength. The attained very promising properties favoured their use on a very high performance car and the presented technique can be further extended for other important challenging applications. The prototype components are produced using T6 heat treated A357 alloy. Results on the samples machined directly from the produced callipers are in detail described and analysed. Pieces exhibiting some small defects, individuated by non-destructive tests, as well as defectless pieces have been underlined to severe industrial tests, e.g. high pressure tight, as well as severe bench tests, and it has been observed that the proposed technological process assure the fulfilment of the requirements contained in standards.