Part of the book: Aluminium Alloys
Part of the book: Manufacturing System
Part of the book: Aluminium Alloys
Part of the book: Aluminium Alloys
Part of the book: Light Metal Alloys Applications
The Al-B4C metal matrix composite (MMC) is characterized by its ability to absorb neutrons which makes it the most suitable shielding material for nuclear reactors. The present work was performed on two series of Al-B4C metal matrix composites made using a powder injection apparatus. In one series, commercially pure aluminum (A5) served as the matrix. For the second set, 6063 alloy was used. In all cases the volume fraction of B4C reinforcement particles (grit size 400 mesh, purity 99.5%) was approximately 15%. The volume fraction of the injected B4C particles was determined using a computer driven image analyzer. Measured amounts of Ti, Zr, and Ti + Zr, were added to the molten composites of both series. Microstructural characterization was carried out employing a field emission scanning electron microscope operating at 20 kV and equipped with an electron dispersive x-ray spectroscopic system (EDS). The same technique was applied to characterize the fracture behavior of the tested composites. Mechanical properties of these composites were investigated using impact testing, and ambient and high temperature tensile testing methods. Almost 1000 impact and tensile samples were tested following different heat treatments. The obtained results from these investigations are reported in this Chapter.
Part of the book: Advances in High-Entropy Alloys
The present work was carried out on A413.1cast alloy that was characterized by short freezing temperature range. Measured amounts of high purity (99.99%) rare earth metals (Ce, La, La + Ce) were added to the non-modified and Sr-modified molten metal. Three casting molds were used viz., graphite mold heated at 600°C for the purpose of obtaining solidification curves, metallic mold with three variable opening angles heated at 350°C, and a step-like metallic mold heated at 200 and 400°C. The main results are earth metals (RE) would lead to porosity formation in all molds with increase in its percentage in Sr-modified alloys. Since the maximum α-Al network formation temperature is in the range of 575–580°C, some of the RE may precipitate in the liquid state leading to blocking the flow of the liquid metal. However, considering the metal was degassed using high purity argon gas, most of the observed porosities are of shrinkage type. In addition, increasing the amount of used RE, and hence percentage of unsoluble intermetallics results in marked decrease in the alloy strength. The only observed advantage is the effectiveness of La is reducing the alloy grain size due to its low affinity to react with Ti.
Part of the book: Recent Advancements in Aluminum Alloys
Grain refining is considered one of the most important liquid metal processing processes for aluminum alloys. Three different types of grain morphology are possible: columnar, twin columnar and equiaxed. The present work reviews most of the theories that were proposed during the past three decades. These theories were mainly based on thermal analysis and thermodynamics to explain the mechanisms of grain refining of Al-Si based alloys, including the role of the master alloy used i.e., Al-B, Al-Ti, and Al-Ti-B alloys. Other aspects were also examined, mainly the interactions between Si and/or Sr and the grain refining master alloy, superheating of the molten metal as well as holding time prior to casting. This phenomenon is normally termed “poisoning” since it reduces the effectiveness of the added grain refiners. The effects of grain refining on the alloy microstructural characteristics, mechanical properties, machinability, hot tearing etc. have not been addressed in the present article.
Part of the book: Recent Advancements in Aluminum Alloys