Correlation of the microhardness with the tensile properties of neutron irradiated molybdenum
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KAZUO FURUYA, Engineer,is with the Nuclear Materials Division, National Research Institate for Metals, Tokyo, Japan. JOHN MOTEFF is professorof Materials Scienceat the University of Cincinnati, Cincinnati, OH 45221. Manuscript submitted May 20, 1980. METALLURGICALTRANSACTIONSA
strength. One is given in terms of the so-called slip line field solution. Dugdale 7 has reported an interesting study on two-dimensional wedge indentation and Shaw et al 8,9 presented a new approach, assuming plasticelastic strain states instead of a plastic-rigid system. Another method, proposed by Cahoon et al~~ is based on the experimental results and the strain hardening behavior of the material. Following the above theories, many studies were made to determine the degree of correlation between the hardness and tensile properties of an austenitic stainless steel 2,4 and for neutron irradiated refractory metals 3,t2.t3 such as Nb, M o and W. Based on the good agreement between the hardness and the strength of various metals and alloys, the next important problem is on the determination of the ductility from the hardness impression. One possible approach was suggested by BOklen24 He proposed one model on the upward plastic metal flow around the indentation. During indenter penetration into the metal, the material deforms plastically near the indenter and a pile-up wall of material is formed close to the impression. The height of the pile-up wall (h) may be related to the work-hardening exponent, i.e. uniform elongation. BOklen used a 100 deg diamond cone as the indenter and found that the value of the impression parameter h / r , the height normalized by impression radius (r), had shown good correlation to the uniform elongation for many kinds of metals such as steels, aluminum and copper alloys. BOklen points out that there is one curve for the nonferrous metals and another for steels, both being independent of a variation of the chemical composition and heat treatment. The purpose of this study is to investigate the correlation of the microhardness with the tensile properties of neutron irradiated molybdenum and to evaluate the degree of correlation of the tensile ductility from the hardness measurements of the contour patterns adjacent to the indentations. 2. E X P E R I M E N T A L P R O C E D U R E S The material investigated in the present study was high-carbon arc-cast molybdenum with the chemical composition as listed in Table I. Before neutron irra-
ISSN 0360-2133/81/0713-1303500.75/0 9 1981 AMERICAN SOCIETY FOR METALS AND THE METALLURGICAL SOCIETY OF AIME
VOLUME12A, JULY 1981--1303
Table I. Chemical Composition of Molybdenum used In the Present Study (ppm) C
0
N
H
Fe
Si
W
Cu
205
3
10
4
~20
5
~100
10
diation, the specimens were annealed at 1473 K in a gettered Argon atmosphere for one hour for recrystallization. The mean grain size was 25/tin. Neutron irradiation was carried out in the Oak Ridge Research Reactor (ORR) at reactor ambient temperature (about 343 K) to a fast neutron fluence fo 1.1 • 1024n.m -2, E ,
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