Effect of densification rate on consolidation and properties of Al7075–B₄C composite powder

Abstract

Hot quasi-static pressing and dynamic compaction of Al7075-B 4 C composite powder are studied in this work. Micron sized Al7075 and B 4 C particles were milled to obtain uniform dispersion of B 4 C reinforcing phase. Samples with relative densities up to 97.5, 99 and 100% were fabricated using gas gun, drop hammer and hot quasi-statically compactions respectively. The results showed that the increase of B 4 C content improved the hardness of the compacts but did not improve the compressive strength in the samples compacted by the gas gun. However, the ductility of the samples was reduced significantly. The samples compacted using the drop hammer and under hot quasi-static loading experienced ,25 and 11% enhancement in the compressive strength respectively. The investigation indicated that the dynamic compaction using the gas gun was more successful if it is performed after quasi-static pre-compaction and under warm compaction process. It was concluded that the quasi-static pressing is the best fabrication technique to achieve the highest density, microhardness and strength.

Evaluation of tensile strength of Al7075-SiC nanocomposite compacted by gas gun using spherical indentation test and neural networks

“…More details about the punch-die assembly for dynamic compaction and the process can be found in Ref. [13]. It must be noted that the samples density was measured using the Archimedes principle [7].…”

“…This sintering procedure may lead to grain growth and agglomeration of the particles that are detrimental to the final quality of the composites [7]. On the other hand, in dynamic compaction techniques such as shock wave consolidation [1,8,9] and high velocity compaction (HVC) [10][11][12][13][14] the sample is not exposed to a longtime sintering temperature and hence, the mentioned defects can be prevented. These processes offer adequate high temperatures for local metallurgical bonding at the powder particle interfaces while the powder remains relatively cool elsewhere [7,15].…”

Reduced order numerical modeling for calibration of complex constitutive models in powder pressing simulations

“…The solution to the minimization problem defined by (4) directly provides values of sought constitutive parameters. Clearly, such formulation provides an important advantage as the material parameters are obtained straight from measured quantities within the powder pressing experiment, with no further experimentation needed on green bodies.…”

“…To overcome this difficulty, specifically designed Genetic Algorithm (GA) was utilized in obtaining the numerical solution of above minimization problem (4). The minimization performed through GA is based on a sequence of "generations" over the parameter search domain.…”

“…Pressing represents mechanical compaction of a powder in order to form the geometrically shaped solid body, called "green body", dimensionally close to the final part, which is obtained after a subsequent phase of sintering at high temperature. This production path is widely applied for manufacturing of various types of materials, including metallic materials through powder metallurgy [1][2], metal/non-metal composites [3][4], since offering larger flexibility when mixing components, ceramic materials [5], with high melting temperature, as sintering is generally performed at temperatures well below the melting one [6][7]. Though it offers diverse advantages, such production is fairly sensitive to the selection of various parameters (e.g.…”