Ricardo Henrique Buzolin

Graz University of Technology | TU Graz · Institute of Materials Science Joining and Forming

The competitive formation of allotriomorphic α along the prior β grain boundaries, secondary α-phase and the growth of globular primary α is described for the Ti-6Al-4V alloy during continuous cooling. The formation kinetics of the different morphologies of the α-phase is related to the nucleation rate of allotriomorphic α and secondary α as well a...

The thermo-mechanical processing of Ti-alloys comprises several steps where complex deformation and temperature cycles are achieved. In this work, the static recrystallization behaviour of a Ti-17 alloy is investigated using ex-situ characterization and in-situ synchrotron radiation experiments aiming to understand the operating mechanisms and to e...

The plastic deformation at high temperatures of two-phase titanium alloys is modelled using a mesoscale approach to describe the complex interactions between different populations of dislocation densities. The static and dynamic recovery, as well as of continuous dynamic recrystallization, is modelled. The flow stresses of both α and β phases are c...

Ti-17 is exposed to microstructural modifications during thermomechanical treatment. In this work, we focus on the characterisation, analysis and modelling of the modifications during plastic deformation in the one phase and two phases domain. Hot compression tests are carried out between 810 °C and 970 °C and at 0.001 s−1 to 10 s−1 up to 0.85 stra...

Two different mesoscale models based on dislocation reactions are developed and applied to predict both the flow stress and the microstructure evolution during the hot deformation of titanium alloys. Three distinct populations of dislocations, named mobile, immobile, and wall dislocations, describe the microstructure, together with the crystal miso...

This work investigates the hot compressive behaviour of a cast high entropy alloy. The alloy is subjected to four different thermomechanical treatments to refine the as-cast microstructure: hot compression tests at constant strain rates (0.001s−1 and 1s−1), hot compression tests with strain rate jumps (between 0.001s−1 and 1s−1), multi-stage hot de...

In this work, microstructural changes during creep of Ni-based alloy 617 at 700 °C and 165 MPa have been investigated by electron microscopy, and complementarily modelled. Precipitate types, sizes and chemistry were determined by transmission- (TEM) and scanning electron microscopy (SEM). Apart from γ’ particles, MX and carbides, coarse μ-phase was...

This work explores the feasibility of producing bead-on-plate welds of a CrCoNi medium entropy alloy and a CrMnFeCoNi high entropy alloy using electron beam welding. The alloys were welded in two states: one in an as-cold rolled condition and the other in an annealed condition. In addition, the high entropy alloy is investigated and welded with two...

The synthesis of bulk nanoporous copper (npCu) from a copper-manganese alloy by electrochemical dealloying and free corrosion as well as the electrochemical behaviour of the dealloyed structures is investigated by in situ resistometry. In comparison to the well-established nanoporous gold (npAu) system, npCu shows strongly suppressed reordering pro...

The objective of this work is to study for the first time the combination of electron beam (EB) surface structuring and plasma electrolytic oxidation (PEO) with the aim of providing a multiscale topography and bioactive surface to the Ti6Al4V alloy for biomedical applications. Ca and P-containing coatings were produced via 45 s PEO treatments over...

During thermomechanical processing of AA6082, the continuous dynamic recrystallization phenomenon is the restoration mechanism following dynamic recovery at high temperatures. This work proposes a microstructure model to describe the evolution of dislocation densities, misorientation distributions, fractions of high and low angle grain boundaries,...

The present work deals with a systematic study to verify the correlation between the pulsed fluxed core arc welding (FCAW) parameters, namely pulse current and frequency, welding speed, and contact tip work distance (CTWD), and the bead morphology, microstructure formation, residual stress, and hardness of the martensitic clad.

Viscoplastic self-consistent (VPSC) modeling was used for investigating the deformation behavior of commercial EN AW-7075-T651 aluminum alloy at room temperature under quasi-static tension and compression (i) parallel, (ii) diagonal and (iii) transverse to the rolling direction. Textures of the as-received plate and of the samples after tensile and...

Additive manufacturing has become increasingly important in the production of magnetic materials in recent years due to the great demands for miniaturization and complex-shaped magnet parts. In this study, the laser beam-powder bed fusion process (LPBF) has been used to develop an in-situ alloying process for the additive manufacturing of a permane...

In present study, the feasibility of wire-based additive manufacturing of commercially pure tungsten using electron beam technique could be demonstrated. Three different representative volumetric AM structures were built and subsequently characterized. The parts show a sound visual appearance with the absence of macroscopic cracks or severe distort...

Wear‐resistant metal matrix composites (MMC) are common engineering materials which have been used for many industrial hardfacing applications. This work provides the detailed characterization of a laser‐clad MMC consisting of hard tungsten carbide particles embedded in a comparatively soft nickel alloy matrix, which has been intended to be used fo...

The low carbon martensitic stainless AWS 410NiMo steel has in its chemical composition 13% chromium, 4% nickel, and 0.4% molybdenum (wt.%) and is used in turbine recovery, rotors, and high-pressure steam pump housings due to its resistance to impact at low temperatures, as well as to corrosion and cavitation. Those applications of the AWS 410NiMo s...

In the present study, the application and tailoring of the alloy composition of chromium martensitic hot-work steels using metal cored wires (MCW) for wire arc additive manufacturing (WAAM) in a modified short-circuit metal transfer process is demonstrated. The nickel content was varied and the alloys were fabricated as tubular-cored wires with var...

The microstructure and mechanical properties of butt-joints produced by linear friction stir welding of similar plates of as-cast ZK60 and modified ZK60 with 1.5 wt.% RE (ZK60–1.5RE) are investigated. The thermomechanical affected zone is investigated in both advancing and retrieving sides, and the microstructure is compared to the base metal and t...

This study investigates the development of the microstructure in the interconnection zone of an IN718/Al/IN718 couple obtained by the Transient Liquid Phase Bonding (TLPB) process at 1000 °C. The crystal structure, composition and orientation of the phases formed during joining were examined by SEM-EDS EBSD. The results showed that the interconnect...

The complex thermal cycles and temperature distributions observed in additive manufacturing (AM) are of particular interest as these define the microstructure and the associated properties of the part being built. Due to the intrinsic, layer-by-layer material stacking performed, contact methods to measure temperature are not suitable, and contactle...

The deformation behaviour of as-cast ZK40 alloys modified with individual additions of Ca and Gd is investigated at 250 • C and 300 • C. Compression tests were carried out at 0.0001 s −1 and 0.001 s −1 using a modified Gleeble system during in-situ synchrotron radiation diffraction experiments. The deformation mechanisms are corroborated by post-mo...

Mg-Zn-Zr (ZK) alloys exhibit notably high mechanical strength amongst all magnesium alloy grades. However, due to the formation of low melting point Mg 3 Zn 7-precipitates, these alloys are susceptible to hot cracking, thus compromising their metallurgical processing. The addition of rare earths to ZK alloys is an alternative to form higher melting...

The growth kinetics of allotriomorphic α along the prior β grain boundaries and of globular primary α in Ti-6Al-4V during continuous cooling is described. A physical model is developed based on classical nucleation and growth of platelets for the allotriomorphic α. The growth of the primary α is modelled based on the growth of spherical particle im...

This work uses flow stresses obtained experimentally at different strain rates and temperatures to validate flow modelling results. Flow curves of Ti6Al4V are measured via torsion experiments with a Gleeble ® 3800 up to effective strains of 8. A physically based model that describes the evolutions of microstructure and the flow stress in the β-phas...

The effect of individual additions of calcium oxide (CaO), Gd, Nd and Y was investigated on the microstructure and corrosion resistance of the as-cast ZK40 alloy. The microstructural features were analysed using scanning electron microscopy. Electrochemical Impedance Spectroscopy, hydrogen evolution and weight loss under immersion in 0.5 wt.% NaCl...

This study investigates the characteristics of the AlNi intermetallic formed in a Ni/Al/Ni couple obtained by the Transient Liquid Phase Bonding (TLPB) process. The crystal structure and orientation of the AlNi intermetallic phase were evaluated through SEM-EDS EBSD and its mechanical properties were analyzed by means of instrumented hardness. The...

AZ91D and MRI153M alloys were produced by thixomolding. Their corrosion resistance is significantly higher than that of similar materials produced by ingot or die‐casting. A corrosion rate smaller than 0.2 mm/year in 5 wt% NaCl solution is measured for the thixomolded AZ91D alloy. The corrosion behaviour was evaluated using immersion tests, electro...

The addition of Zn to the Mg–Nd system improves the yield strength and creep resistance, however its influence on the intermetallic phases in the ternary system is not yet fully understood. Understanding the sequence of phase-formation and phase-evolution during solidification and processing is essential to microstructure design. The solidification...

The microstructure of Al-Si-Mg alloys strongly depends on their chemical composition and the heat treatment they undergo during production. The influence of solution heat treatment (SHT) and the addition of Er and Zr on the microstructure of gravity-cast A356 (Al-7Si-0.4Mg) were examined. The reference as-cast microstructure is characterized by the...

Electron beam processing (EBP) was applied on two different cast magnesium alloys (AZ91 and ZKX50) followed by subsequent heat treatment (HT). The microstructure and corrosion properties of the alloys in all of the conditions were investigated by standard microscopy and electrochemical measurements. After EBP, a uniform and significantly refined mi...

A physical based model is developed to describe recrystallization phenomena of titanium alloys during hot working of the β phase. Continuous dynamic recrystallization is attributed as the restoration mechanism based on the progressive transformation of low angle boundaries (subgrains) into high angle boundaries (grains). The model describes both, t...

The following paper describes a new and effective method to obtain high-density sinters with simultaneously decreased distortions, produced by one press and sinter operation. This effect was achieved through the induced disappearance of the eutectic liquid phase. The study was carried out on AISI 316L stainless steel powder that was mixed with elem...

This paper presents a new production method for a spherical and monocrystalline aluminum powder. Aluminum powder of irregular particle shapes was mixed with silica nanoparticles and heated to a temperature above the melting point of aluminum. Due to its molten state, high surface tension, and poor wettability, the aluminum particles were transforme...

Rotary friction welding is a solid state welding process where the required heat for welding is generated by friction caused by the relative movement between a stationary part and its rotary counterpart. As the melting temperature is not reached, this welding technique does not produce typical welding defects known from fusion welding. In the case...

This work deals with the analysis and modelling of the microstructural evolution of the metastable titanium alloy Ti-5Al-5V-5Mo-3Cr during hot deformation up to moderate and large strains. Experimental flow curves and deformed samples are obtained by hot compression and hot torsion tests using a Gleeble ® 3800 device. The samples are deformed above...

Mg-4Nd base alloys with Zn additions of 3, 5 and 8 wt % were investigated with in situ synchrotron radiation diffraction during solidification. This method enabled the investigation of phase formation and transformation in the alloys. The diffraction results were supported with TEM observations on the as-solidified samples. The results show the eff...

The influences of Er and Zr additions on the corrosion behavior of A356 (Al‐7Si‐0.4Mg) alloy are investigated. Electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy), gravimetric analyses, and microstructural investigations demonstrate that 0.3 wt% Er nominal addition is beneficial for the corrosion resistan...

The mechanical properties of as-cast Mg-4Nd-xZn (x = 0, 3, 5 or 8 wt.%) alloys were investigated both in situ and ex situ in as-cast and solution-treated conditions. The additions of 3 or 5 wt.% Zn in the base Mg-4Nd alloy did not improve yield strength in comparison to the binary Mg-4Nd alloy. Mechanical properties were shown to improve only with...

The microstructure and mechanical properties of dissimilar butt-joints of high-strength low-alloy steel to austenitic high Mn TRIP steels produced by manual TIG welding with AISI 309L filler metal were investigated. The heat input was varied by changing the welding current between 40 and 70 A. A fully austenitic microstructure with nearly equiaxed...

As-cast ZK40 alloys, modified with the addition of CaO, Gd, Nd and Y were investigated. Solution heat treatments were performed based on differential thermal analysis results. The unmodified ZK40 alloy exhibited microstructure with nearly no intermetallic compound but with precipitates formed during the solution treatment. The modified ZK40 alloys...

The microstructures of as-cast ZK40, ZK40 with 2% (mass fraction) CaO and ZK40 with 1% (mass fraction) Y were investigated, and the intermetallic phase morphology and the distribution were characterised. By having discrete intermetallic particles at the grain boundaries for the ZK40, the microstructure was modified to a semi-continuous network of i...

An AM60 magnesium alloy nanocomposite reinforced with 1 wt % of AlN nanoparticles was prepared using an ultrasound (US) assisted permanent-mould indirect-chill casting process. Ultrasonically generated cavitation and acoustic streaming promoted de-agglomeration of particle clusters and distributed the particles throughout the melt. Significant grai...

Mg-rare earth alloys have improved yield strength and creep resistance compared to commercial alloys such as AZ91, AM60 or AS21. The influence of Zn additions in Mg–Nd alloys on intermetallic phases and the resulting changes in the macroscopic mechanical behaviour of the materials are not yet fully understood. The aim of this work is to identify th...

In this work, a combination of in situ experiments; synchrotron diffraction and synchrotron tomography were used to study the solidification behaviour of Mg-5Nd-5Zn (wt. %). The samples were cooled with a cooling rate of 100 °C/min and 5 °C/min in the in situ synchrotron diffraction experiment and in situ synchrotron tomography experiments respecti...

The effect of a travel speed of 200 mm/min as well as a tool rotational speed of 1200 rpm on butt joint quality of friction stir welding (FSW) ZK60 magnesium casting alloy containing 1.5 wt.% rare earths (ZK60-1.5RE) was investigated to determine microstructure and residual stresses. FSW results in the generation of heterogeneous metallurgical stru...

The properties of commercially viable Mg alloys are not sufficient for many of the envisaged applications. The combination of Zn and rare earth metals is one of the most effective ways to enhance the mechanical properties of Mg alloys. In situ synchrotron radiation diffraction is a unique method to investigate the dynamic microstructural processes...

Process optimization is one pathway to maximizing strength of a given alloy. Thixomolding® is a semi-solid casting process that combines pores reduction with a typical bimodal grain size distribution that can lead to enhanced strength. AZ91D and AZX911 were processed via Thixomolding® using two different processing conditions to change fraction sol...

The microstructure and mechanical properties of dissimilar butt-joints between a high strength low alloyed (HSLA) grade and an austenitic high Mn TRIP steel were investigated. The tool rotation and the tool offset toward the TRIP steel were varied between 300–500 rpm and 1–2 mm, respectively. Tool advancing speed amounted to 100 mm/min. Maximum ten...

Solution treatments (T4) at 380 °C for 16 h and 500 °C for 8 h were performed for ZK60 magnesium alloys modified with addition of 0.5, 1.5 and 2.5 wt% of mischmetal (combination of rare-earth (RE) elements). The compression behaviour was investigated at room temperature and at 300 °C correlated with the microstructure and differential scanning calo...

As-cast Mg5Nd, Mg5Nd3Zn, Mg5Nd5Zn and Mg5Nd7Zn alloys were investigated with in situ synchrotron radiation diffraction during compression at 350°C. The results and the post-mortem microscopy investigations suggest that twinning was active during deformation, and was most pronounced in the binary alloy whereas in the ternary alloys grain rotation co...

A homemade procedure for manufacturing of mechanical replacement parts was developed. The approach was applied to a guide ruler installed in machinery to produce steel rod frames. The guide ruler part, which is produced by the original manufacturer of the equipment, acts as an alignment guide of the steel wires. It ensures that the steel wires can...

As-cast ZK40, ZK40-2Gd and ZK40-2Nd Mg alloys were investigated by in situ synchrotron radiation diffraction during compression at elevated temperature. The addition of rare earth elements increased the compressive yield strength from 23 MPa in the ZK40 alloy up to 40 MPa in the alloy with Nd or Gd. The azimuthal angle–time plots and electron back...

As-cast Mg-4Zn-0.5Zr, Mg-4Zn-2Gd-0.5Zr and Mg-4Zn-2Nd- 0.5Zr alloys were investigated by in situ synchrotron radiation diffraction during hot compression at 350 °C using the facilities of P07 beamline of Petra III at Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany. The specimens were heated at a rate of 100 K/min and compressed with an in...

As-cast Mg-4Zn-0.5Zr, Mg-4Zn-2Gd-0.5Zr and Mg-4Zn-2Nd-0.5Zr alloys were investigated by in situ synchrotron radiation diffraction during hot compression at 350 °C using the facilities of P07 beamline of Petra III at Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany. The specimens were heated at a rate of 100 K/min and compressed with an ini...

Rare earth elements reportedly improve high temperature strength and creep resistance of Mg alloys. In the present work, ZK60 Mg alloys containing different amounts (0.5, 1.5 and 2.5 wt.%) of rare earth additions were prepared by thixocasting and submitted to solution and ageing heat treatments (T4, T5 and T6). The as-cast and heat treated microstr...