Crystallizing Metal Shrinkage: Automation of High-Pressure Crystallization Control

The properties of bulk metal products are formed when molten metal transforms from an unstructured liquid into a solid crystal state. We suggest a new approach to the automation of the control over crystallized metal shrinkage compensation based on controlling the law of change in pressure applied to crystallizing metal through a program taking into account the transition process in the hydraulic system of the production equipment. We observed the increase in rigidity, durability, and pliability of В95-alloy samples as compared to cast aluminum alloys. The metal utilization rate can be increased up to 0.90 of the liquid metal volume.

Studying the process of modification of lithium aluminum alloys

The effect of modification with dispersed compositions on the grain structure and mechanical properties of industrial aluminum alloys has been studied. Aluminum alloys of the Al-Si, Al-Mg-Sc, Al-Cu-Mn systems were modified with dispersed Mg2Si powder with a particle size of up to 200 nm. The amount of modifier to be added to the melt is calculated. The physicochemical properties of dispersed Mg2Si have been studied. Melting of the AMg6, 1570, 2219, AK9ch alloys in the initial state and with the treatment of Mg2Si melts have been carried out. The action of insoluble applications, isomorphic to aluminum, the similarity of the influence of soluble elements holds only when the amount of insoluble addition exceeds the number of crystals formed arbitrarily under the same conditions. Thus, with an increase in the amount of insoluble addition, in particular silicon carbide particles, the grain size first decreases and then remains constant. The mechanism of the influence of dispersed particles of magnesium silicide on the formation of the structure of hypoeutectic aluminum alloys during crystallization is that their bulk is pushed out by the crystallization front into the liquid phase and participates in the refinement of the structural components of the alloy. To determine the optimal amount of silicon carbide modifier, industrial melting and testing were performed on specimens that underwent heat treatment according to the T6 mode (quenching and artificial aging). The quality of cast aluminum alloys during modification depends on many factors: the nature of the dispersed phase, the temperature of the melt, and the modes of its mixing with the introduction of particles. Dependences of the particle size and the amount of the modifier on the mechanical properties of the alloys have been established. The mechanism of interaction of the modifier with aluminum melt during crystallization has been established. In industrial experiments, the most effective size of SiC particles for increasing the σm of the AK9ch alloy from 115 to 260 MPa in the as-cast state has been established. The optimal content of Mg2Si (0.10 %) for increasing the σm of aluminum alloys has been determined.

Possibilities to Apply Friction Stir Processing FSP in Surface Engineering

The results obtained by ISIM Timisoara to the development of the friction stir welding process (FSW) have supported the extension of the researches on some derived processes, including friction stir processing (FSP). The experimental programs (the researches) were developed within complex research projects, aspects regarding the principle of the process, modalities and techniques of application, experiments for specific applications, being approached. The paper presents good results obtained by friction stir processing of cast aluminum alloys and copper alloys. The optimal process conditions, optimal characteristics of the processing tools were defined. The complex characterization of the processed areas was done, the advantages of the process applying being presented, especially for the cast aluminum alloys: EN AW 4047, EN AW 5083 and EN AW 7021. The characteristics of the processed areas are compared with those of the base materials. The results obtained are a solid basis for substantiating of some specific industrial applications, especially in the automotive, aeronautical / aerospace fields.

Processes Developed Based on Friction Stir Welding Process

Considering the remarkable results obtained by using friction stir welding process (FSW), ISIM Timisoara has developed research programs for the knowledge and development of processing processes based on the FSW process principle.The paper presents a synthesis of the researches and the results obtained within some of research projects carried out by ISIM Timisoara, regarding possibilities of using some of processes derived from the FSW process, which has focused mainly on two directions (areas): surface engineering (materials surface processing) and joining by friction riveting. In the field of surfaces engineering, there are presented some results that represent own contributions of ISIM Timisoara, regarding: friction stir processing as well as coating with functional layers from lightweight alloys of steel substrates (by friction with consumable tool).Regarding friction riveting, two methods are presented: classic friction riveting, respectively friction riveting with hybrid effect (mechanical grip and friction welding).The paper shows very good results obtained to FSP processing (for cast aluminum alloys), to friction riveting with hybrid effect (for aluminum and copper alloys) and to friction riveting (for aluminum alloy), but also some limitations of these friction processing methods.Also in the paper are presented new research directions that are currently being addressed, respectively that will be addressed in the next period at ISIM Timisoara, regarding new variants of application of FSW welding.

The Effect of the β-Al5FeSi Phases on Microstructure, Mechanical and Fatigue Properties in A356.0 Cast Alloys with Higher Fe Content without Additional Alloying of Mn

Secondary-cast aluminum alloys have increasing industrial applications. Their biggest deficiency is their impurity content, especially Fe, which has low solubility in Al and almost all the content creates intermetallic phases. This work examines the effect of higher Fe content on the microstructure and properties of A356.0 alloy. At the same time, no other possibility existed to affecting the brittleness of the formation of the β phases. The calculation of Fecrit, ratio of Mn/Fe, quantitative and computed tomography analysis of porosity and Fe plate-like phases, measurement of mechanical and fatigue properties, and fractography analysis were performed in this study. The results show that gravity die casting into a sand mold, and the non-usage of Mn addition or heat treatment, do not have a negative effect on increasing the size of the Fe-rich plate-like phases. The longest Fe-rich phases have limited the pore growth and ratios, but their higher thickness led to greater porosity formation. The mechanical and fatigue properties correlate with the Fecrit level and the highest were for the experimental alloy with 0.454 wt.% of Fe. The experimental results confirmed the fact that if the Fe plate-like phases have a length of up to 50 µm, the fatigue properties depend more on the size of porosity. If the length of the Fe needles is more than 50 µm, then the properties are mainly affected by the length of these Fe phases.