Improving strain hardening behavior in nano-intermetallic reinforced aluminum in-situ composites through an optimized twostep thermal processing method; sintering and uniaxial forging

Abstract

Excellent strain hardening capabilities are known to be the unique strategies to hold the key towards a good strength-ductility balance in Al−base composites. Herein, in-situ Fe-aluminide (FeAl) reinforced Al−matrix composites (Al/Fe-aluminide) were fabricated by a twostep thermal processing method: sintering (900 °C/1 h), and uniaxial forging (400 °C, deformation up to 20%). The reinforcements were formed in-situ by the exothermal reaction between the host Al matrix and Fe2O3 nanoparticles during sintering Measured strain rate sensitivity (m= 0.035)and strain rate recovery rate (ηr)highlighted that deformation during forging enhances strain hardening ability of the composites. Comprehensive characterization reveals high density of geometrically necessary dislocation (ρG∼1×1015m−2) usually persists near the grain boundaries (GBs) and the triple junctions of highly textured FCC−Al grains. Microtextural and Kernel average misorientation (KAM) measurements highlighted existence of strong deformation texture of Bras {110}<112> and Goss {110}<001>2 in FCC−Al matrix induce strong resistance to plastic deformation. While nanoindentation response based on plastic flow corresponding to activation volume (V*∼42b3) revealed that activities of GB interface−dislocation interaction induced strain accumulation at the FCC−Al GB interface zones involved in a thermally activated process promotes the evolution of ρGdistribution during straining sustain larger strains. The results reveal that the simultaneous attainment of both these processes improves global strain hardening behavior which is advantageous for the enhancement of resistance to failure.