Influence of Coarse Second Phase Additions on Mechanical Properties of NiAl
- PDF / 2,178,804 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 114 Downloads / 194 Views
INFLUENCE OF COARSE SECOND PHASE ADDITIONS ON MECHANICAL PROPERTIES OF NiAI H.CLEMENS*, I.RUMBERG*, P.SCHRETIER*, P.GRAHLE**, O.LANG**, A.WANNER**, AND E.ARZT** * Metallwerk Plansee GmbH, A-6600 Reutte, Austria. ** Max-Planck-Institut fUr Metallforschung, Institut fUr Werkstoffwissenschaft, Seestral3e 92, D-7000 Stuttgart 1, Germany. ABSTRACT NiAI/Nb and NiAI/Cr composite materials were prepared by a powder metallurgical approach. The content of the second phases varied between 5 and 10 weigth percent. The thermodynamic stability of Nb and Cr particles in the NiAI matrix was studied at 1473K (1200°C) by means of SEM, XRD and microhardness measurements. In the case of Nb the formation of a Laves phase (NbNiAI) was observed whereas the Cr particles remained stable but were hardened to a remarkable extent due to in-diffusion of Ni and Al. This paper presents the results of three-point bending tests performed on as-HIPed and annealed material at room temperature and elevated temperatures. The yielding behavior at room temperature and the creep behavior at 1200K (927QC) were investigated by compression tests. INTRODUCTION Intermetallic aluminides, especially NiAl, are attractive candidate materials for high temperature applications. The main advantages of NiAl are the low density, excellent thermal conductivity and oxidation resistance. In order to improve mechanical properties the effects of Cr and Nb as second phase additions were investigated. EXPERIMENTAL PROCEDURE NiAl/Cr and NiAI/Nb composite material was prepared by blending gas-atomized NiAI powder with Cr or Nb powder. The content of the second phases varied between 5 and 10 weight percent (in volume percent: 4.1 - 8.3 for Cr; 3.4 - 7 for Nb). In the case of Cr, powders with two different particle fractions have been used. Typical impurity concentrations and average particle sizes of the powders are given in Table I. Table I: Chemical analysis and average particle size of powders used.
O (ppm) N (ppm) H (ppm) average particle
size (pm)
NiAl 185 10 3 73
Cr
Data Loading...
