Short communication Micromechanical, high-temperature testing of steel–TiB 2 composite sintered by high pressure–high temperature method Iwona Sulima a,n , Grzegorz Boczkal b a Institute of Technology, Pedagogical University of Cracow, Podchorazych 2 Street, 30-084 Krakow, Poland b AGH University of Science and Technology, Faculty of Non-Ferrous Metals, Krakow, Poland article info Article history: Received 24 May 2015 Received in revised form 15 July 2015 Accepted 17 July 2015 Available online 21 July 2015 Keywords: Metal matrix composites Sintering Grain boundaries Deformation and fracture abstract The study compares the mechanical properties of steel–TiB 2 composites sintered by high pressure–high temperature method. The mechanical characteristics of materials were determined in a tensile test at temperatures ranging from 20 to 900 °C. The results show that, depending on the degree of conversion of the composite components, the construction of the grain boundaries is changing and, at the same temperature of the tensile test, various hardening mechanisms are operating. Strain-temperature char- acteristics are completely different in both cases. & 2015 Elsevier B.V. All rights reserved. 1. Introduction Powder metallurgy offers new opportunities for the production of advanced composite materials designed for operation at high temperatures and high mechanical loads. Several modern tech- nologies using high pressure have been developed, including, among others, the high pressure–high temperature method (HP– HT) [1,2]. High-pressure sintering processes use the phenomenon of the inhibited grain growth and accelerated densification of the processed material. The main advantage of HP–HT sintering is the possibility of achieving simultaneously in a single process a very high value of both pressure and temperature. Under such condi- tions, the effective time required to carry out the sintering process is very short, not exceeding, in fact, a few minutes. Sinters ob- tained by this method are characterised by a nearly hundred- percent degree of compaction [3]. As a matrix of composite materials, austenitic steels are in- creasingly being used. They offer very good mechanical properties and corrosion resistance [4]. One of the best steel reinforcing phases used in the composite materials is titanium diboride. The TiB 2 ceramics has high hardness (3400 kg/mm 2 , inferior only to the hardness of diamond, BN and B 4 C), low density (4.5 g/cm 3 ), high mechanical strength (750 MPa) and high modulus of elasti- city (345–409 GPa), excellent abrasive wear resistance, good wettability, and stability of bond formed with the steel matrix [5,6]. So far, studies have focused on the steel matrix composites with the TiB 2 phase content exceeding 10 vol% [7,8]. Most of the authors have discussed the technologies used for the fabrication of such materials and impact of the sintering parameters on the composite physical properties and microstructure. The effect of the TiB 2 ceramic material on the tribological properties of the steel matrix composites [9] was also investigated. In composite mate- rials, most important is the determination of their mechanical properties. In cases where the use of modern methods of sintering (e.g. HP–HT) allows obtaining sinters of a small size only, the methods used for the preparation of micro-samples and testing of mechanical properties in micro-scale are both time-consuming and complicated. And yet, speaking in terms of the later applica- tion of such composites, testing of their mechanical properties is the matter of an utmost importance. It also results from the need to determine the effect of the sintering technology and of the re- inforcing TiB 2 phase on the mechanical characteristics of compo- site materials. The main objective of the present study was to investigate the mechanical properties of composites based on an austenitic stainless steel, reinforced with 2 vol% of TiB 2 . Mechanical tests were carried out in a wide range of temperatures, since the target application of the sintered composites would be operation at high temperatures. To optimise the methodology of sample preparation and conducting the research in micro-scale, one variant of the composite with a small amount of TiB 2 (2 vol%) was selected. Lit- erature offers little information about the micro-scale, high-tem- perature testing of the mechanical properties of composite materials. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/msea Materials Science & Engineering A http://dx.doi.org/10.1016/j.msea.2015.07.047 0921-5093/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: gboczkal@agh.edu.pl (G. Boczkal). Materials Science & Engineering A 644 (2015) 76–78