Effects of cold compacting pressure on the expansion behavior of Ti-48Al during sintering

Microstructure Evolution and Pore Formation Mechanism of Porous TiAl3 Intermetallics via Reactive Sintering

“…It is shown that the specimen sintered at 600°C for 1 h had a slight volume expansion of 27.5% and the radial and axial expansion increased to 6.2 and 13.1%. It indicated that the diffusion reaction between Ti and Al elements occurred and triggered the Kirkendall effect [24]. Furthermore, it is noted that the volume expansion ratio increased sharply with increasing temperature to TE and reached to the maximum value of 69.3%, as well as the radial expansion of 16.8% and axial expansion of 24.1%.…”

“…Careful observation revealed that the AC section can be divided into rising stage along with the furnace temperature (AB) and stable stage (BC) around the melting point of Al (660°C). This can be explained by the endothermic effect representing the melting of Al overlaps the heat released from the specimen body [24]. In consequence, the actual temperature of specimen was almost suppressed and cannot see the rising trend.…”

“…Then, a small endothermic peak at 661°C appeared on account of the melting of aluminum. Ye et al [24] reported that the melting of Al transforms the reaction mechanism to a liquid-solid reaction, which proceeds at a much higher rate. Novoselova et al [25] have studied the thermal response of Ti-50Al at.% powder using two different heating rates of 5 and 20°C/min.…”

“…Similar results were also obtained in previous findings [22], and the former studies only analyzed the preparation and influence of macropores on pore structures. Furthermore, previous researches have largely concern about the sintering conditions of synthetic porous Ti-Al materials such as heating rate, compacting pressure, sintering temperature and content of raw materials [21,23,24,26]. However, three types of pores formed during this sintering process, and their (Fig.…”

“…Additionally, porous Ti-Al intermetallics are typical brittle materials and exist an inverse relationship between mechanical strength and porosity [36]. Ye et al [24] carried out the compressive test as a function of compacting pressure and concluded that the increase in pressure on green compact will result in the higher sintering density as well as the lower porosity, meanwhile, the compressive strength will be improved. According to the reactive synthesis of Ti-75Al at.% powders from room temperature to 1100°C, the steps of the pore formation process can be described as shown in Fig.…”