Effect of Holding Time on Densification, Microstructure and Selected Properties of Spark Plasma Sintered AA7075-B4C Composites

Abstract

The paper presents the effect of the holding time, varying between 1 min 15 s and 10 min, on the microstructure evolution and development of selected properties of spark plasma sintered AA7075-based composites reinforced with 3, 5 and 10 wt% sub-micro B4C powder. The sintering temperature and the compaction pressure were 500 °C and 80 MPa, respectively. Composites with a near full density of 96–97% were obtained. Microstructure studies were performed employing the techniques of light microscopy and scanning electron microscopy, along with an analysis of the chemical composition in micro-areas. Additionally, the phase composition was investigated by means of X-ray diffraction. In addition, hardness and flexural strength tests were performed. It was found that the holding time did not significantly influence the microstructures of the examined materials nor the hardness or flexural strength. The sintered composites had a fine-grained microstructure with a strengthening phase located at the grain boundaries. As a result of the spark plasma sintering process, fine precipitates of intermetallic phases were also observed in the aluminum grains, suggesting partial supersaturation, which occurred during fast cooling.

Development of iron-based composite materials through electromagnetic radiations in a domestic microwave oven

“…The maximum porosity was obtained for Iron-based SS316+10EWAC1004+5Cr7C3 composite (1.98%) and the least for Iron-based SS316 (0.99%). Earlier, Wąsik et al 79 prepared AA7075-based composites reinforced with B 4 C using SPS and claimed porosity >3%. Kumaran et al 84 prepared 316 SS–B 4 C composite using the powder metallurgy route and found porosity <5%.…”

“…Zhang et al 78 claimed that suppressed grain size has more grain boundaries, energy, strength, and hardness. Earlier researchers Wa ˛sik et al 79 claimed grain size 50-70 mm of AA7075-based composites reinforced with B 4 C prepared by SPS. Hwang et al 80 obtained 88.51 mm of Stainless Steel 316L processed by metal powder injection molding (MIM) sintered for 2 h at 1320°C.…”