長大結晶粒積層組織を有するMo板の高温強度 High-Temperature Strength of Molybdenum Sheets with Elongated Coarse-Grain Structures
Molybdenum sheets with two types of elongated coarse-grain structures (trade name: TEM) were developed by heavy-duty rolling and recrystallization treatment of sintered molybdenum bodies with 1mass% La<SUB>2</SUB>O<SUB>3</SUB>. One type of sheets has spindle-like grains (S-TEM), and the other has stacked, plate-like grains (P-TEM). Tensile tests were carried out on S-TEM and P-TEM at 1470K to 2070K in vacuum to investigate the effects of grain structure on tensile properties such as proof strength (σ<SUB>y</SUB>), tensile strength (σ<SUB>m</SUB>) and uniform elongation (δ<SUB>m</SUB>) at high temperatures. The aspect ratio (L<SUB>TD</SUB>/W, L<SUB>RD</SUB>/W) of grains, i.e., ratio of grain length (L) to grain width (W) on the transverse plane and perpendicular plane to the rolling direction, were estimated as a parameter of grain structure. The following results were obtained.<BR>(1) TEM with elongated coarse-grain structures (S-TEM and P-TEM) had a higher σ<SUB>y</SUB> and σ<SUB>m</SUB> than pure molybdenum and TZM with equiaxial-grain structures. At 2070K, the σ<SUB>y</SUB> and σ<SUB>m</SUB> of TEM were 2-3 times those of pure molybdenum.<BR>(2) The σ<SUB>y</SUB> and σ<SUB>m</SUB> of TEM increased with increased L<SUB>TD</SUB>/W, and strain hardening was difficult to perform with increased L<SUB>RD</SUB>/W.<BR>(3) Three distinct failure modes were found. The higher the test temperature, the smaller the reduction area in the case of S-TEM with small L<SUB>TD</SUB>/W grains. In P-TEM with large LTD/W grains, the reduction was not dependent on temperature, although P-TEM indicated a larger reduction compared to S-TEM. In pure molybdenum and TZM, the higher the test temperature, the larger the reduction.
粉体および粉末冶金 46(5), 489-495, 1999-05-15
Japan Society of Powder and Powder Metallurgy