Valerio Volpe - Academia.edu (original) (raw)

Papers by Valerio Volpe

Surface Engineering, 2014

ABSTRACT The purpose of this work is to characterise the colours obtained on the surface of zinc–... more ABSTRACT The purpose of this work is to characterise the colours obtained on the surface of zinc–titanium alloy coatings. Hot dip galvanising samples were prepared at temperatures in the range of 560–640°C. Seven colours were observed and objectively measured by means of reflectance curves and CIELab coordinates. Experimental results show that, after the extraction from the bath, the colours of the galvanised coating change continuously during the cooling and then stabilise after a few seconds. The colour uniformity on the surface of each sample was evaluated according to ASTM standard. Results show little colour differences in two specimens and acceptable colour uniformity in the other five.

L'acciaio in atmosfera, senza opportuna protezione, subisce una degradazione spontanea e tecn... more L'acciaio in atmosfera, senza opportuna protezione, subisce una degradazione spontanea e tecnicamente irreversibile, che causa, in tempi più o meno brevi, un'inesorabile e progressiva perdita delle proprietà tipiche dello stato metallico. La scelta della migliore tecnologia anti-corrosiva è una misura preventiva di primaria importanza per progettisti, realizzatori e committenti sia pubblici che privati. Il rivestimento che si forma sull'acciaio non è semplicemente deposto, come avviene con le vernici o i rivestimenti elettrolitici: durante l'immersione dei manufatti nel bagno, lo zinco si lega intimamente all'acciaio attraverso la formazione di fasi intermetalliche. Vasto campo di applicazione è quello costituito dalle strutture zincate nei servizi, nell'arredo urbano e sulle strade. Le reti stradali sono disseminate di materiale zincato che consiste in barriere di sicurezza, guardrail e new jersey metallici, ma anche recinzioni fonoassorbenti, griglie di del...

Generally speaking the rockfall protection net wires are Zinc or Zn-Al coated. This provides to t... more Generally speaking the rockfall protection net wires are Zinc or Zn-Al coated. This provides to the net a durable protection against corrosion. Due to their function, the rockfall protection nets can be damaged over time, and must be replaced. The aim of this work is to investigate the damage that the wire undergoes when subjected to "U" bending, in order to obtain a significant stress. Furthermore it has been analyzed the behavior of a Zn-high Al coating in comparison with the coatings normally used. SOMMARIO. I fili delle reti paramassi vengono rivestiti con Zn puro o con leghe Zn-Al 5% per proteggerli dall'aggressione dell'ambiente esterno. Le reti, proprio a causa della funzione che svolgono, possono rovinarsi nel tempo, e devono quindi essere sostituite. In questo lavoro si è indagato il danneggiamento che subisce il rivestimento del filo se sottoposto a piegatura ad "U", in modo da ottenere una sollecitazione sensibile. In particolare si è analizzat...

Corrosion Science, 2014

ABSTRACT Elemental zinc and copper–zinc alloys capped with a mixed-oxide layer of cuprite and zin... more ABSTRACT Elemental zinc and copper–zinc alloys capped with a mixed-oxide layer of cuprite and zincite were exposed to SO2 vapour in a humid oxygen-free atmosphere. Elemental sulphur, zinc sulphite and some zinc hydroxide are the only products which are obtained in the anoxic sulphitation of metal zinc. The pseudo-binary system Cu2SO3Cu(1−x)ZnxSO3⋅2H2O is the result of the experiments on both thermally oxidised and naturally weathered α-brasses. The outcome of competition between the high-copper and the high-zinc species strongly depends on the mass action law: the greater the ZnO to Cu2O phases ratio, the higher the substitution rate of Cu(II) for Zn(II).

Some Cu-Zn-Al alloy is able to exhibit an important feature: the Pseudo-Elastic behavior, commonl... more Some Cu-Zn-Al alloy is able to exhibit an important feature: the Pseudo-Elastic behavior, commonly defined as PE alloy. The PE effect is the result of a non-diffusion microstructure changing characterized by a good reversibility at environmental temperature. Furthermore, the copper-based shape memory alloys are preferred for their good memory properties and low cost of production. In this work, fatigue crack propagation and microstructural fracture micromechanisms are analyzed in order to identify microstructure influence on fatigue behavior of Cu-Zn-Al PE alloy.

Frattura ed Integrità Strutturale, 2014

ABSTRACT In recent years, mechanical property of many SMA has improved in order to introduce thes... more ABSTRACT In recent years, mechanical property of many SMA has improved in order to introduce these alloys in specific field of industry. Main examples of these alloys are the NiTi, Cu-Zn-Al and Cu-Al-Ni which are used in many fields of engineering such as aerospace or mechanical systems. Cu-Zn-Al alloys are characterized by good shape memory properties due to a bcc disordered structure stable at high temperature called β-phase, which is able to change by means of a reversible transition to a B2 structure after appropriate cooling, and reversible transition from B2 secondary to DO3 order, under other types of cooling. In β-Cu-Zn-Al shape memory alloys, the martensitic transformation is not in equilibrium at room temperature. It is therefore often necessary to obtain the martensitic structure, using a thermal treatment at high temperature followed by quenching. The martensitic phases can be either thermally-induced spontaneous transformation, or stress-induced, or cooling, or stressing the β- phase. Direct quenching from high temperatures to the martensite phase is the most effective because of the non-diffusive character of the transformation. The martensite inherits the atomic order from the β-phase. Precipitation of many kinds of intermetallic phases is the main problem of treatment on cu-based shape memory alloy. For instance, a precipitation of α-phase occurs in many low aluminum copper based SMA alloy and presence of α-phase implies a strong degradation of shape recovery. However, Cu-Zn-Al SMA alloys characterized by aluminum contents less than 5% cover a good cold machining and cost is lower than traditional NiTi SMA alloys. In order to improve the SMA performance, it is always necessary to identify the microstructural changing in mechanical and thermal conditions, using X-Ray analyses. In this work a Cu-Zn-Al SMA alloy obtained in laboratory has been microstructurally and metallographically characterized by means of X-Ray diffraction and Light Optical Microscope (LOM) observations. Furthermore a fatigue crack propagation and fracture surface scanning electron microscope (SEM) observations have been performed in order to evaluate the crack path and the main crack micromechanisms.

SOMMARIO Il presente lavoro riguarda uno studio preliminare degli effetti della corrosione in amb... more SOMMARIO Il presente lavoro riguarda uno studio preliminare degli effetti della corrosione in ambienti contenenti SO 2 su acciai zincati a caldo con substrato zincato danneggiato. Il danneggiamento è stato ottenuto mediante usura con contatto di strisciamento non lubrificato effettuato per mezzo di un tribometro sperimentale tipo ball on disk. Il danneggiamento è stato effettuato in maniera tale da portare allo scoperto le varie fasi intermetalliche Fe-Zn. Le prove di corrosione sono state effettuate seguendo la norma EN ISO 6988 (prova Kesternich). La morfologia della corrosione ottenuta è stata caratterizzata mediante analisi SEM-EDS. INTRODUZIONE Uno dei sistemi più utilizzati per proteggere manufatti in acciaio dalla corrosione è quello di rivestirli con un sottile strato di zinco. L'acciaio in questo modo viene ad essere protetto dall'aggressione elettrochimica dell'ambiente sia attraverso un effetto barriera, esercitato dal rivestimento di zinco, sia attraverso un ...

Several kinds of materials are employed for the realization of orthopedic internal prosthesis. Ti... more Several kinds of materials are employed for the realization of orthopedic internal prosthesis. Titanium and Titanium alloys are widely used for their chemical-physical properties. These materials have low density, high strength, non magnetic behavior and high corrosion resistance in the human body environment. In the paper are reported failure analyses of a titanium spinal prosthesis employed as support on the treatment of a vertebral lesion. The prosthesis premature and unexpected failure has required its removal and replacement. Optical and electron microscopy has been employed in order to characterize the material microstructure and to study the fracture morphology. Mechanical tests have been carried out on the prosthesis in order to evaluate its mechanical strength. Similar tests have been performed on a spinal prosthesis coming from another producer.

I materiali a memoria di forma sono leghe metalliche caratterizzate dalla capacità di recuperare ... more I materiali a memoria di forma sono leghe metalliche caratterizzate dalla capacità di recuperare la forma iniziale anche a seguito di elevate deformazioni. Se ne possono distinguere due tipi: le leghe che per recuperare la forma hanno bisogno di essere riscaldate al di sopra di una temperatura critica e quelle in grado di recuperare la forma iniziale semplicemente togliendo il carico applicato. Nel prima caso le leghe sono generalmente definite a comportamento a memoria di forma SMA (Shape Memory Alloy), mentre nel secondo caso sono definite leghe PE (Pseudo Elastic). In questo lavoro sono state effettuate caratterizzazioni metallografiche, di microdurezza e di struttura mediante analisi diffrattometrica ai raggi X e di una lega CuZnAl a comportamento PE prodotta in laboratorio. In particolare la caratterizzazione strutturale è stata effettuata sulla lega allo stato indeformato, sotto carico e dopo rottura.

Cu–Zn–Al shape memory alloys exhibit shape memory behavior within a certain range of composition.... more Cu–Zn–Al shape memory alloys exhibit shape memory behavior within a certain range of composition. They are characterized by a stable high temperature disordered bcc structure named β-phase, followed by a transition to a B2 structure after appropriate cooling and from secondary B2 to DO3 ordering under other cooling procedures. It is also know that martensite stabilization can be reduced by a step-quenched treatment. Shape memory properties are often absolutely interesting and many grades of shape memory alloys are extensively used in the technological world, e. g. in surgery and dentistry. Copper-based shape memory alloys are preferred for their good memory properties and low cost of production. In this work, the main crack initiation and its propagation in an tensile test is analyzed in order to evaluate crack path and its behavior corresponding to low and to high deformation values. Furthermore, results are associated to X-Ray diffraction in order to correlate structural transitio...

The purpose of this paper is to study the phase transformation induced by the cold rolling of a C... more The purpose of this paper is to study the phase transformation induced by the cold rolling of a Cu-Zn-Al alloy fabricated in our laboratories. Flat specimens were made from the alloy. They were subsequently heat treated at 850°C/20 min, quenched in water at 100°C, treated at 320°C/30 min, quenched in water at 100°C, cooled in air up to room temperature. To correlate the microstructure variations with the entity of the imposed deformation, the samples were cold rolled selectively (each 2.5%) up to 15% of deformation. On each cold rolled sample, the microstructures were investigated by LOM and XRD. The deformation has contributed to β 3 (L 21) ordering of the structure and to occur the martensitic transformation. The martensite obtained is the M18R type. This result shows that the parameter which most influences the type of obtainable martensite is determined by the order of the parent phase. During testing it was found that the martensite enucleates in appreciable quantities even at ...

Procedia Engineering, 2015

Surface Engineering, 2014

Chapter in Books by Valerio Volpe

Acta Fracturae, Jul 1, 2013

The purpose of this paper is to study the phase transformation induced by the cold rolling of a C... more The purpose of this paper is to study the phase transformation induced by the cold rolling of a Cu-
Zn-Al alloy fabricated in our laboratories. Flat specimens were made from the alloy. They were subsequently
heat treated at 850°C/20 min, quenched in water at 100°C, treated at 320°C/30 min, quenched in water at
100°C, cooled in air up to room temperature.
To correlate the microstructure variations with the entity of the imposed deformation, the samples were cold
rolled selectively (each 2.5%) up to 15% of deformation. On each cold rolled sample, the microstructures were
investigated by LOM and XRD. The deformation has contributed to β3 (L21) ordering of the structure and to
occur the martensitic transformation. The martensite obtained is the M18R type.
This result shows that the parameter which most influences the type of obtainable martensite is determined by
the order of the parent phase. During testing it was found that the martensite enucleates in appreciable
quantities even at a level of deformation of 2.5% of the specimen. An increase of the martensite up to a
deformation of 15% was observed. It has not been possible to continue beyond this level of deformation, due
to the presence of transgranular cracks.

Acta Fracturae, Jul 1, 2013

"Some Cu-Zn-Al alloy is able to exhibit an important feature: the Pseudo-Elastic behavior, commo... more "Some Cu-Zn-Al alloy is able to exhibit an important feature: the Pseudo-Elastic behavior,
commonly defined as PE alloy. The PE effect is the result of a non-diffusion microstructure changing
characterized by a good reversibility at environmental temperature. Furthermore, the copper-based shape
memory alloys are preferred for their good memory properties and low cost of production.
In this work, fatigue crack propagation and microstructural fracture micromechanisms are analyzed in order to
identify microstructure influence on fatigue behavior of Cu-Zn-Al PE alloy."

Acta Fracturae, Jul 1, 2013

Pseudo-elastic (PE) materials are an important class of metallic alloy which exhibit unique featu... more Pseudo-elastic (PE) materials are an important class of metallic alloy which exhibit unique features
with respect to common engineering metals. Because of these unique properties, PEs are able to recover their
original shape after high values of mechanical deformations, by removing the mechanical load (PE). From the
microstructural point of view shape memory and pseudo-elastic effects are due to a reversible solid state
microstructural diffusionless transitions from austenite to martensite, which can be activated by mechanical
and/or thermal loads. Copper-based shape memory alloys are preferred for their good memory properties and
low cost of production.
This paper describes the main crack initiation and its propagation in an tensile test in order to evaluate crack
path and its behaviour at low and at high values of deformation. Both grain boundary chemical properties and
X-ray diffraction will be discussed in order to correlate structural transition involved in an Cu-Zn-Al alloy
characterized by a PE behaviour.

Conference Proceedings by Valerio Volpe

13th International Conference on Fracture, Jun 16, 2013

Cu–Zn–Al shape memory alloys exhibit shape memory behavior within a certain range of composition.... more Cu–Zn–Al shape memory alloys exhibit shape memory behavior within a certain range of composition. They are characterized by a stable high temperature disordered bcc structure named β-phase, followed by a transition to a B2 structure after appropriate cooling and from secondary B2 to DO3 ordering under other cooling procedures. It is also know that martensite stabilization can be reduced by a step-quenched treatment. Shape memory properties are often absolutely interesting and many grades of shape memory alloys are extensively used in the technological world, e. g. in surgery and dentistry. Copper-based shape memory alloys are preferred for their good memory properties and low cost of production.
In this work, the main crack initiation and its propagation in an tensile test is analyzed in order to evaluate crack path and its behavior corresponding to low and to high deformation values. Furthermore, results are associated to X-Ray diffraction in order to correlate structural transition involved in an Cu-Zn-Al alloy characterized by a PE behavior.

Surface Engineering, 2014

Corrosion Science, 2014

Frattura ed Integrità Strutturale, 2014

Procedia Engineering, 2015

Surface Engineering, 2014

Acta Fracturae, Jul 1, 2013

The purpose of this paper is to study the phase transformation induced by the cold rolling of a C... more The purpose of this paper is to study the phase transformation induced by the cold rolling of a Cu-
Zn-Al alloy fabricated in our laboratories. Flat specimens were made from the alloy. They were subsequently
heat treated at 850°C/20 min, quenched in water at 100°C, treated at 320°C/30 min, quenched in water at
100°C, cooled in air up to room temperature.
To correlate the microstructure variations with the entity of the imposed deformation, the samples were cold
rolled selectively (each 2.5%) up to 15% of deformation. On each cold rolled sample, the microstructures were
investigated by LOM and XRD. The deformation has contributed to β3 (L21) ordering of the structure and to
occur the martensitic transformation. The martensite obtained is the M18R type.
This result shows that the parameter which most influences the type of obtainable martensite is determined by
the order of the parent phase. During testing it was found that the martensite enucleates in appreciable
quantities even at a level of deformation of 2.5% of the specimen. An increase of the martensite up to a
deformation of 15% was observed. It has not been possible to continue beyond this level of deformation, due
to the presence of transgranular cracks.

Acta Fracturae, Jul 1, 2013

13th International Conference on Fracture, Jun 16, 2013

Cu–Zn–Al shape memory alloys exhibit shape memory behavior within a certain range of composition.... more Cu–Zn–Al shape memory alloys exhibit shape memory behavior within a certain range of composition. They are characterized by a stable high temperature disordered bcc structure named β-phase, followed by a transition to a B2 structure after appropriate cooling and from secondary B2 to DO3 ordering under other cooling procedures. It is also know that martensite stabilization can be reduced by a step-quenched treatment. Shape memory properties are often absolutely interesting and many grades of shape memory alloys are extensively used in the technological world, e. g. in surgery and dentistry. Copper-based shape memory alloys are preferred for their good memory properties and low cost of production.
In this work, the main crack initiation and its propagation in an tensile test is analyzed in order to evaluate crack path and its behavior corresponding to low and to high deformation values. Furthermore, results are associated to X-Ray diffraction in order to correlate structural transition involved in an Cu-Zn-Al alloy characterized by a PE behavior.

XXIII Convegno Nazionale Trattamenti Termici, Oct 19, 2011

Rivestimenti zinco-titanio. Effetto della temperatura sulla morfologia e sul colore delle superfici

13th International Conference on Fracture, Jun 16, 2013

Cu–Zn–Al shape memory alloys exhibit shape memory behavior within a certain range of composition.... more Cu–Zn–Al shape memory alloys exhibit shape memory behavior within a certain range of composition. They are characterized by a stable high temperature disordered bcc structure named β-phase, followed by a transition to a B2 structure after appropriate cooling and from secondary B2 to DO3 ordering under other cooling procedures. It is also know that martensite stabilization can be reduced by a step-quenched treatment. Shape memory properties are often absolutely interesting and many grades of shape memory alloys are extensively used in the technological world, e. g. in surgery and dentistry. Copper-based shape memory alloys are preferred for their good memory properties and low cost of production.
In this work, the main crack initiation and its propagation in an tensile test is analyzed in order to evaluate crack path and its behavior corresponding to low and to high deformation values. Furthermore, results are associated to X-Ray diffraction in order to correlate structural transition involved in an Cu-Zn-Al alloy characterized by a PE behavior.

34° Convegno Nazionale AIM, Nov 7, 2013

Leghe CuZnAl, memoria di forma, pseudoelasticità SOMMARIO I materiali a memoria di forma sono leg... more Leghe CuZnAl, memoria di forma, pseudoelasticità SOMMARIO I materiali a memoria di forma sono leghe metalliche caratterizzate dalla capacità di recuperare la forma iniziale anche a seguito di elevate deformazioni. Se ne possono distinguere due tipi: le leghe che per recuperare la forma hanno bisogno di essere riscaldate al di sopra di una temperatura critica e quelle in grado di recuperare la forma iniziale semplicemente togliendo il carico applicato. Nel prima caso le leghe sono generalmente definite a comportamento a memoria di forma SMA (Shape Memory Alloy), mentre nel secondo caso sono definite leghe PE (Pseudo Elastic). In questo lavoro sono state effettuate caratterizzazioni metallografiche, di microdurezza e di struttura mediante analisi diffrattometrica ai raggi X e di una lega CuZnAl a comportamento PE prodotta in laboratorio. In particolare la caratterizzazione strutturale è stata effettuata sulla lega allo stato indeformato, sotto carico e dopo rottura.

Workshop IGF “Problematiche di frattura ed integrità strutturale di materiali e componenti ingegneristici, Mar 1, 2012

Ductile cast irons (DCIs) are able to combine the toughness of steels with the good castability o... more Ductile cast irons (DCIs) are able to combine the toughness of steels with the good castability of
gray irons. They are widely used in a number of applications, e.g. wheels, gears, crankshafts in cars and trucks
etc. DCIs fatigue crack propagation resistance depends on loading conditions, chemical composition, matrix
microstructure and graphite elements morphology (graphite volume fraction, graphite elements nodularity,
graphite elements distribution and dimension). In this work, a ferritic DCI was investigated focusing fatigue
crack propagation micromechanisms: step by step fatigue crack propagation tests were performed considering
Compact Type specimens and micromechanisms were investigated by means of Scanning Electron Microscope
(SEM) lateral surface observation.

Giornate Nazionali sulla Corrosione e Protezione (AIM), Jul 6, 2011

La zincatura a caldo è una delle tecniche commercialmente più importanti usate per proteggere i c... more La zincatura a caldo è una delle tecniche commercialmente più importanti usate per proteggere i componenti esposti in ambienti corrosivi. Il rivestimento, ottenuto per immersione in un bagno di zinco fuso, garantisce una protezione durevole, resistente e utilizzabile in un vastissimo campo di applicazioni, grazie alla formazione durante il processo di uno strato compatto formato da fasi intermetalliche (Γ, δ, ζ, η) che riveste completamente il manufatto. Negli ultimi anni è sorto un interesse ad ottenere rivestimenti colorati per componenti utilizzati soprattutto nel settore delle costruzioni, o comunque atti a soddisfare requisiti estetici richiesti in alcune applicazioni. In questo lavoro è stata valutata l'aggiunta al bagno di zincatura dello 0,5 % in peso di titanio, in quanto è stato così possibile ottenere dei rivestimenti colorati. Lo studio effettuato intende verificare la resistenza del colore e il comportamento a corrosione di alcuni campioni quando sono sottoposti a prova in anidride solforosa con condensazione generale di umidità (camera Kesternich). Il colore del rivestimento è stato misurato tramite la valutazione delle curve di riflettanza e quantificato con tecniche di colorimetria CieLab. La raccolta dei dati è stata effettuata prima dell'inizio delle prove di corrosione e al termine delle stesse.