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Tham khảo tài liệu 'volume 06 - welding, brazing and soldering part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Alloy 909. The most prominent member of this group is nickel-iron Alloy 909. It is primarily used for seals and rings aircraft turbines. Its low coefficient of expansion allows close-tolerance designs which increase the fuel efficiency of turbine engines. Mechanically Alloyed Products. The final group of precipitation-hardening alloys to be discussed merits the nam superalloys. Mechanically alloyed products have a remarkable advantage over conventional materials in elev temperature stress-rupture strength. This advantage is gained by the combination of precipitation hardening dispersion strengthening. Neither concept is revolutionary but the combination of the two using the ball mill is. As Shi in Fig. 1 various ingredients are added to the ball mill as metallic and intermetallic powders. Extended processing t of approximately 10 h in the mill cause the particles to become metallurgically homogeneous. This process is simil the step of incorporation in Du Pont s early approach to making homogenous particles of gunpowder each containir correct ratio of charcoal sulfur and potassium nitrate. Homogenization in the mill is followed by either hot rolling or extrusion. The form is then thermally treated at 1315 2400 F to produce the exceptional strength characteristics. Tables 3 and 4 list the chemical compositions and sell properties for mechanically alloyed products. TABLE 3 COMPOSITION OF SELECTED MECHANICALLY ALLOYED MATERIALS ALLOY COM POSH riONS WT Fe Cr Al Ti Ni c Y2O3 MO MA 754 1.0 20.C 0.3 0.5 BAL 0.05 0.6 MA 956 BAL 20.0 4.5 0.5 0.5 MA 957 BAL 14.0 1.0 0.25 0.3 MA 6000 15.0 4 5 2.5 BAL 0.5 0.6 TABLE 4 PROPERTIES OF SELECTED MECHANICALLY ALLOYED MATERIALS ALLOY DENSITY YOUNG S MODULUS TENSILE strength A YIELD strength A ELONGATION AT FRACTURE A STRESS TO PRODUCE RUPTURE AT 1095 2000 F FOR INDICATED ELAPSED TIME 100 H 1000 H G CM3 LB IN.3 GPA 106 PSI MPA KSI MPA KSI MPA KSI MPA KSI MA 754 B 8.3 0.30 149 21.6 148 21.5 134 19. 5 12.5 02 1048 13.6 MA 95ờB 7.2 0.26 .