G. Maizza

Politecnico di Torino | polito · DISAT - Department of Applied Science and Technology

The growing interest in nanocrystalline (nc) materials is driven by their outstanding combination of mechanical and functional properties. Electrodeposited nc Ni–Fe alloys have received considerable attention, thanks to their unique strength and to their thermal and magnetic properties. However, the research on the relationship between microstructu...

The tool industry strongly demands more economical, high‐performance, healthy, and ecological Co‐free WC‐based composites. Nickel is considered the optimal substitute of Co in WC‐based cermets to attain nearly comparable, if not superior properties in terms of wear resistance and fracture toughness. The combination of WC‐Ni with spark plasma sinter...

Spark plasma sintering (SPS) is a versatile and effective rapid processing technique to sinter nanostructured thermoelectric (TE) materials. This paper presents a combined experimental and modelling investigation of the Peltier effect during SPS processing of TE materials. The Peltier effect is related to the transport of heat by an electric curren...

In this paper it is described the experimental procedure and the statistical method for the measurement of indentation modulus by using the primary hardness standard machine at INRIM, in the macro-scale range. Indentation modulus is calculated on the basis of Doerner-Nix linear model and from accurate measurements of indentation load, displacement,...

Commercial titania powders were calcined in order to investigate the influence of the heating history on the thermally stable phase (rutile). Temperatures from 620 to 700 °C and heating rates from 50 to 300 °C/h were used in order to evaluate their influence on the kinetics of transformation and microstructure evolution. The quantitative analysis o...

Multimaterial components are more suitable than monolithic materials to combine several mechanical and functional properties simultaneously. Bi-layer components made of WC-Co and steel can combine enhanced wear resistance and toughness, which are beneficial for a wide range of advanced tribo-structural applications. In this study, a new solid-state...

Elastic modulus is one of the most important parameters evaluated by instrumented indentation test. This paper refers to its measurement in the macro range, where, missing adequate reference materials, traceability proposed by ISO 14577-1 cannot be applied. In this condition, the uncertainty evaluation shall be performed by propagating the uncertai...

γ-TiAl alloys have been subject of numerous studies as they are candidate materials for high temperature applications in the transportation industry. However, they suffer very low ductility at room temperature and can rapidly oxidize thereby increasing strength and decreasing ductility further. Industrial applications of γ-TiAl entail accurate on-...

Bulk and contact multiphysics is of great theoretical and technological interest to many engineering applications, such as spot welding, current-assisted powder metallurgy, electrical circuitry (switches), electrical motors, etc. A multifield model is developed with the aim of predicting material properties changes in a steel sample subjected to a...

Instrumented indentation, also known as depth-sensing indentation, is increasingly used as an alternative non-destructive test method to measure mechanical properties of small volumes of materials. It is widely used to determine the hardness equivalent to conventional ones as well as to measure the indentation hardness, the Martens hardness, the in...

Capacitor Discharge Sintering (CDS) is an ultrafast electric current assisted sintering method (ECAS) suited for electrically conductive metallic and metal-ceramic composite powders. The technique is a solid state near net shape sintering process which is in general characterized by a very short discharge time (tens of milliseconds), very high curr...

For the first time we have demonstrated the densification of high‐purity nanostructured (davg ≈ 60 nm) tungsten carbide by High Pressure Spark Plasma Sintering (HPSPS) in the unusually low temperature range of 1200°C–1400°C. The high‐pressure sintering (i.e., 300 MPa) produced dense material at a temperature as low as 1400°C. In comparison with mor...

A new method was developed to fully consolidate binderless tungsten carbide and diamond powders by means of spark plasma sintering (SPS) in current‐control mode (CCm). Below 900°C, the 2 cm diameter sample was slowly heated by a dc current of 1000 A. Above 900°C the imposed current was suddenly raised to 4000 A. The combination of the relatively hi...

A new method was developed to fully consolidate binderless tungsten carbide and diamond powders by means of spark plasma sintering (SPS) in current-control mode (CCm). Below 900°C, the 2 cm diameter sample was slowly heated by a dc current of 1000 A. Above 900°C the imposed current was suddenly raised to 4000 A. The combination of the relatively hi...

Recently, the number of published papers on the sintering technologies activated by current have increased exponentially. In particular, it has been reported that the application of electric field as high as 120 V/cm permitted the instantaneous full densification of yttria stabilized tetragonal zirconia at the unusual low temperature of 850 degrees...

The intricate bulk and contact multiphysics of spark plasma sintering (SPS) together with the involved non-linear materials’ response make the process optimization very difficult both experimentally and computationally. The present work proposes an integrated experimental/numerical methodology, which simultaneously permits the developed SPS model t...

Capacitor Discharge Sintering (CDS) is an ultrafast Electric Current Assisted Sintering method (u-ECAS) suited for electrically conductive powders. It is characterized by relatively short processing times (milliseconds range) and much lower sintering temperatures than the melting point of the powders. However, the CDS basic phenomena are not fully...

A more predictive capability required in the control of sintering process of complex parts and the simulations presented for solid state sintering through finite element modeling was discussed. It was found that simulation procedures represented a useful supporting tool for process optimization while the computational methods for the simulation of...

A wireless optical emission diagnostic apparatus has been developed for in-situ diagnosis of the high gravity (HG) plasma properties during diamond chemical vapor deposition using H2–CH4 gas mixture. Optical emission spectroscopy (OES) enabled us to identify the emitting chemical species and to qualitatively investigate the plasma composition chang...

Microstructural changes and resulting properties were studied for SAF 2205 (UNS S31803) austeno-ferritic stainless steel (SS) aged between 700 C and 900 C for up to 2 weeks and then water-quenched. Quantitative metallography coupled with x-ray diffraction techniques were adopted to follow ferrite ([alpha]) transformation with subsequent formation o...

The prediction of the property changes of structural materials, after service in a fusion reactor, is a key point for the technological development of this power source. The interaction of the fusion neutrons with the first wall, in particular, is a central problem. A comparison of neutron damage in different fusion fuel cycles is carried out. A co...

Bombardment of a solid by nuclear radiation causes alterations in its physical properties. The damage pattern and some of the resulting effects may be remarkably different, depending upon the type of bombarding particles, their energy and their charge. The principal mechanisms of radiation damage are examined, with their effects on the material pro...

The induction heating model described herein couples the standard heat conduction equation with electro-magnetic proximity-skin equations. An Inverse Finite Element procedure, which is based on prior deterministic and probabilistic concepts, has been designed to solve the inherent inverse equation model with respect to the unknown coil current para...

For their magnetic field coils, fusion reactors need structural alloys working at low temperatures. Austenitic and ferritic steels, aluminium and titanium alloys are the most studied materials. Some of the problems associated with neutron flux exposure of the magnets are addressed, specifically neutron activation and heat deposition. With reference...

Powder metallurgy is a key technology for manufacturing advanced TiAl-based engineering components. Cold compaction is the primary step to produce green parts. However TiAl powders possess intrinsic poor room temperature ductility. On compaction, plastic deformation and cracking susceptibility of TiAl particles strongly depends on their micro-mecha...

The instrumented indentation testing of γ-TiAl imposes the use of large loads only possible with diamond pyramidal indenters. The geometry of such indenters (e.g. Vickers indenter) has to be precisely defined. In addition, the so-called zero-point of the loading curve (i.e. the first point of the indenter coming into contact with the sample) has to...

The increasing demand for improved metallurgical products strongly motivates the optimization of manufacturing processes and design of γ-TiAl products. Among the large variety of available forming processes, cold closed-die forging is particularly suitable for producing net shape bulk products having good surface finish with better mechanical prope...

The study of semi-solid aluminum and magnesium alloy systems is of scientific and technological importance since they exhibit enhanced castability as well as superior mechanical properties compared to conventional ones owing to their refined microstructure. When a metallic melt undergoes severe shear during solidification a refined microstructure u...

The excessive presence of residual SiC matrix inter-fiber pores is often the main cause for the very poor mechanical strength and toughness of SiC/SiC composites manufactured by CVI process. The use of numerical modeling, for optimizing both the CVI process and the material properties, poses further problems related with the presence of two very di...