Influence of Different Filler Metals on the Mechanical and Microstructural Characteristics of Arc-Welded Joints Made of Dissimilar Titanium Alloys

In the motorsport industry, the choice of material for manufacturing the heat resistant components often falls on titanium alloys. In most cases, the production flow for this kind of part involves CNC machining and subsequent assembly by welding process, to other parts obtained by cold plastic forming and possibly made using different titanium alloys. Hence, the alloying element-content in the joint area can be extremely heterogeneous and variable point-by-point. To investigate this topic further, dissimilar welding of the alpha/beta alloy Ti6Al4V and of the oxidation-resistant alpha alloy KS-Ti 1.2 ASN-EX was made by GTAW technology and using different filler metals. Chemical and mechanical properties of the welds were investigated by XRD, SEM-EDS, microhardness maps, and tensile and bending tests. Results show that, despite the different alloying elements present in the two filler wires investigated, static properties of the welds are similar. Results also show that the local V/Al content ratio affects the microhardness as it is responsible for the creation of supersaturated alpha phases during the cooling of the weld beads

SPS-assisted Synthesis of SICp reinforced high entropy alloys: reactivity of SIC and effects of pre-mechanical alloying and post-annealing treatment

In this work a traditional high entropy alloy (FeCoNiCrAl) was reinforced by uniformly distributed reactive silicon carbide (SiC) particles by a powder metallurgy synthetic route, using as precursors simply mixed powders or mechanically prealloyed ones. The reactive sintering produced a single isomorphic BCC structure. The sample microstructure resulted equiassic, more homogenous in samples based on prealloyed powders. The instability of SiC in the presence of metal precursors resulted in the formation of more stable carbides and silicides, as well as in carbon diffusion in the high entropy alloy matrix and partially unreacted SiC particles. The formation of these newly formed fine precipitates, as well as the presence of residual SiC were useful to increase the hardness of the alloy

Driving Innovation through Big Open Linked Data (BOLD): Exploring Antecedents using Interpretive Structural Modelling

YesInnovation is vital to find new solutions to problems, increase quality, and improve profitability. Big open linked data (BOLD) is a fledgling and rapidly evolving field that creates new opportunities for innovation. However, none of the existing literature has yet considered the interrelationships between antecedents of innovation through BOLD. This research contributes to knowledge building through utilising interpretive structural modelling to organise nineteen factors linked to innovation using BOLD identified by experts in the field. The findings show that almost all the variables fall within the linkage cluster, thus having high driving and dependence powers, demonstrating the volatility of the process. It was also found that technical infrastructure, data quality, and external pressure form the fundamental foundations for innovation through BOLD. Deriving a framework to encourage and manage innovation through BOLD offers important theoretical and practical contributions

Wheat husk: A renewable resource for bio-based building materials

The huge annual production of wheat husk in Europe (10 million tons) creates management problems. Valorization options are thus sought. Here, insulting lime concrete was designed using native wheat husk as lightweight aggregate. Physical-chemical and technological properties of both particles and concretes were determined. Comparisons with hemp concrete manufactured with the same process were made. Similar thermal conductivities for the two types of concretes were obtained (ca. 0.09 W/(m·K)), whereas slightly lower compressive strength was found for wheat husk concrete due to weaker particle-binder interface. Nevertheless, results highlight the high potential of raw wheat husk for development of bio-based materials with interesting performances

n situ synchrotron powder diffraction study of the thermal decomposition of cement-asbestos: Preliminary results

The elimination of asbestos-containing materials like cement-asbestos, is an environmental priority. An industrial process for the safe recovery of cement-asbestos slates was recently developed and permits the thermal transformation of asbestos fibres into non-fibrous crystalline phases in a tunnel kiln. Optimisation of the process requires knowledge of the reaction dynamics. Here, time-resolved synchrotron powder diffraction was used to follow the thermal transformation of cement-asbestos. The use of a closed capillary as sample holder allowed to closely resemble the atmospheric conditions found in the industrial reactor. In this preliminary work, we describe the reaction sequence which undergoes cementasbestos during its thermal decomposition. The excellent time resolution of the collected data allowed the observation of meta-stable phases at non-ambient conditions. \ua9 by Oldenbourg Wissenschaftsverlag, M\ufcnchen

Hydration kinetics and microstructural development of a magnesium oxysulfate cement modified by macromolecules

Magnesium oxysulfates (MOS), obtained by hydration of MgO in MgSO4 solution, are highly interesting as binders in lightweight building materials due to their environmental sustainability and promising technological properties. Recent focus has been concentrated on tailoring the phase composition towards 5Mg(OH)2·MgSO4·7H2O (517 phase) by using various additives (e.g. citric acid) that generally act as retarders of the direct hydration of Mg(OH)2, a competing phase in this system. In this work, macromolecules of vegetal origin were investigated as possible retarders to promote the crystallization of the 517 phase. Isothermal and semi-adiabatic hydration experiments were performed, together with thorough microstructural investigations of hardened cements by electron microscopy techniques (SEM, TEM) as well as X-ray powder diffraction and quantitative phase analyses by Rietveld refinements. The results show a temperature and time dependent retardant effect that is only effective in promoting the crystallization of the 517 phase at ambient temperature. Implications for the manufacturing of lightweight concrete are discussed

Lightweight concretes based on wheat husk and hemp hurd as bio-aggregates and modified magnesium oxysulfate binder: Microstructure and technological performances

Using lightweight building materials from ecological resources reduces the environmental impact of buildings. Most attention has been paid to lime-based agro-concretes, but low binder-aggregate compatibility as well as slow strength gain are drawbacks. The use of magnesia-based binders has the potential to mitigate these problems. Here, a modified magnesium oxysulfate (MOS) cement was used to manufacture lightweight concretes using wheat husk, a highly available and unexploited resource, and hemp hurd as bio-aggregate. A combined microstructural-technological study was performed, filling gaps in existing literature. Through microstructural observations made by X-ray Powder Diffraction, microscopy imaging (optical, electron) and mercury porosimetry, mechanical and thermal properties in the different concretes were elucidated. It will be shown that the developed lightweight concretes are technologically competitive with lime-based ones, having the advantage of possessing high early strength

Thermal behaviour of mineral fibres

This chapter deals with the synthesis and thermal stability ofmineral fibres. The different structural assemblages within mineral fibres and their resistance to high temperature changes fromspecies to species. In general, the formation of such minerals takes place in hydrothermal environments. The thermal decomposition process consists of three main stages: the loss of water adsorbed on the surface of the fibre and the zeolitic water below 200250ºC; the removal of the structure water (the hydroxyl groups) in the range 5001100ºC and recrystallization into new stable crystalline phases. The thermal stability of chrysotile, amphiboles fibres and erionite will be described in detail and will be followed by specific sections describing how the concept of thermal decomposition is used for the remediation of wastes containing asbestos to produce secondary raw materials to be recycled in various industrial application

Kinetic study of the drying process of clay bricks

This work deals with the drying kinetics of three red clays with different mineralogical composition and grain size distribution used for the production of clay bricks. The kinetic study was performed using thermo-gravimetry (TG) in both non-isothermal and isothermal mode in the 50-200 °C range. To the knowledge of the authors, this is the first time that the drying process of clay bricks is studied using the TG method to present a general model at molecular scale of the phenomenon. The observed drying mechanism is composed of a fast initial step and a slow final step. The former is characterized by an Avrami-like mechanism with an Avrami coefficient n 1 comprised between 1 and 2. This kinetic parameter indicates a diffusive control in three dimensions with instantaneous or deceleratory nucleation and refers to desorption of adsorbed water from the surface of all mineral phases. The second step is also characterized by an Avrami-like mechanism with n 2 = 1 and points to a diffusion-controlled reaction in two dimensions, with instantaneous nucleation. This step involves dehydration of plastic clay minerals such as illite, smectite and IS through diffusion of water molecules within the two-dimensional interlayer. The apparent activation energies related to the first fast mechanism have similar values ( 35 kJ mol -1 . The dependency of the apparent activation energies on grain size distribution and sample mass was also assessed

In-house synthesis of CoCrFeNi ingots using an electric furnace

Bulk Multi-Principal Element Alloys (MPEAs) are generally synthesized by casting, a process needing specific equipment. Here, a standard laboratory electric furnace was used to synthesize bulk CoCrFeNi by melting of prealloyed powders followed by natural cooling. The use of prealloyed powders guaranteed atomic-level mixing. In accordance with the literature, the resulting ingot had a face-centered cubic structure. A typical dendritic-interdendritic microstructure was obtained which was explained by partitioning during solidification and grain boundary wetting phenomenon. Post-annealing treatment improved chemical homogeneity without crystallographic phase change. This work shows the feasibility of melt-aided synthesis of CoCrFeNi HEA under static conditions using a conventional laboratory furnace