Effect of pore structure on mechanical properties of porous TiAl G. L. Hao 1* , Q. P. Xu 1 , H. Wang 2 and X. Y. Li 1 Based on two sets of TiAl powder, two kinds of porous TiAl were separately fabricated by powder metallurgical route including four stages. The porous TiAl with single pore structure (SPS) was prepared using pre-alloyed TiAl powder prior mechanical ball milling. Another porous TiAl with composite pore structure (CPS) was manufactured depending on composite mixture of Ti/Al elemental powders. The sintering was achieved at much lower temperature for the pre-alloyed power than for the elemental composite mixture. Compressive mechanical tests indicate that much higher mechanical strength can be obtained for SPS than for CPS at the same porosity. It was suggested that the difference of mechanical properties is ascribed to the variety of the compressive deformation process. Keywords: TiAl porous materials, Sintering, Microstructure, Mechanical property Introduction TiAl intermetallic compound porous materials are attracting more and more attention due to an increasing targeted demand. 1–10 The materials can be expected to use as membrane separation materials, catalyst carriers, thermal insulation materials, lightweight structural materials, etc. due to their outstanding intrinsic features, such as high specific strength and specific stiffness, good corrosion and wear resistance, high temperature resist- ance and oxidation resistance. 11–16 The efficient use of the TiAl porous material requires a detailed understand- ing of their mechanical property, even when the primary application is not mechanical but functional. TiAl porous materials are typical brittle porous material that high mechanical strength, especially upper yield strength, is of great importance to meet practical demands. 17 How- ever, there always exists an inverse relationship between mechanical strength and porosity for porous materials. 18 As a result, in order to obtain high mechanical strength at the same porosity, numerous studies havebeen concen- trated on tailoring pore structures by changing prep- aration technique. 19–23 For example, Nakajima fabricated porous TiAl with cylindrical pores oriented along a single direction via unidirectional solidification. It was found that the TiAl porous materials with the direc- tional pores can obtain an increased mechanical strength compared to that prepared by elemental powder metal- lurgy (EPM). 19,22 In our previous study, a new kind of TiAl porous material with a novel double pore structure has been orig- inally prepared using EPM technique. The mechanism of making pores can be described as a combination of repli- cation of space holders and Kirkendall effect. 24 The suit- able sintering temperature was discussed and confirmed as around 1400°C. Similar sintering temperature can also be found in porous Ti–48Al–6Nb (at.-%) alloys man- ufactured by EPM. 11,12,25,26 Although the temperature ranging from 1350 to 1400°C can guarantee a desirable sintering quality, higher sintering temperature means higher requirements to sintering equipment and atmos- phere, and also means more product cost and energy con- sumption. 27 In practice, meeting these requirements is quite difficult in many cases. As a consequence, decreas- ing sintering temperature is greatly expected and mean- ingful. Guyon et al. 28,29 found that 100% densification of TiAl powder can be achieved via spark plasma sinter- ing at the same condition, but 200°C earlier for the ultra- fine-grained powders additionally mechanically grinded by high energy ball milling than for the coarse-grained atomised powder. In view of the dependence of sintering temperature on powder states, in the present work two kinds of TiAl powder, pre-alloyed powder and composite mixture of Ti/Al elemental powders, were prepared as parent materials. Correspondingly, two kinds of TiAl por- ous material with different pore structures were, respect- ively, fabricated by powder metallurgy technique. One is single pore structure (SPS) basing on pre-alloyed TiAl powder, and another with composite pore structure (CPS) was obtained depending on the composite mixture of Ti/Al elemental powder. In addition, the dependence of pore structure on mechanical properties of the TiAl por- ous materials was investigated to clarify the influence of TiAl powder state on TiAl porous materials. Materials and experimental details The nominal chemical composition of the TiAl porous materials is Ti 52 Al 48 (at.-%). Ti and Al elemental powders 1 College of Physics and Electronic Information, Yan’an University, Yan’an 716000, P. R. China 2 State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, P. R. China * Corresponding author, email glhao@issp.ac.cn © 2016 Institute of Materials, Minerals and Mining Received 15 July 2015; accepted 12 December 2015 DOI 10.1080/02670836.2015.1132588 Materials Science and Technology 2016 1