Tailorable elastic modulus of aluminum matrix composites via creation of interfacial intermetallic compounds

The modulus is an intrinsic parameter of metals and alloys and is often difficult to be tailored by conventional alloying method. A feasible strategy to increase the elastic modulus (E) of metals and alloys is to introduce hard, high-modulus ceramics. However, these traditional ceramic reinforcers often have poor interfacial bonding with the base alloy and are difficult to control the content and distribution. In this paper, ductile NiTi particle (NiTip) was added in pure Al alloy by ball milling and spark plasma sintering (SPS). The modulus of the NiTi/Al composite was modulated via in-situ tailorable interfacial reaction and formation of different contents and types of intermetallic compounds between NiTip and Al during SPS process. The composite sintered at 530 °C for 10 min (530 °C-10 min) was free of interfacial reaction product. While the 560 °C-10 min composite showed 100–500 nm thick reaction layer composed of Al-Ti and Al-Ni compounds (in-situ interfacial phase content ∼5.2 vol%). At even higher sintering temperature, the 600 °C-10 min composite exhibited 3–10 μm thick interfacial reaction layer (in situ interfacial phase content ∼36.8 vol%). As a result, the E of the 600 °C-10 min composite reached 107.21 GPa and was 58.34 % higher than that of the 530 °C-10 min composite (67.71 GPa). The increase of E is mainly attributed to the introduction of the interfacial Al-Ti and Al-Ni intermetallic compounds in the composite formed during SPS. The interfacial reaction also enhanced the interfacial bonding strength between NiTip and Al matrix, which is also favorable for the composite modulus.