Pergamon scripta~~~et~Vol.33,No.7,~.1127-1132,1995 ELsevia Scie.nce Ltd ~~gg!!jy?$gf~Inc. 0956-716x&v $9.50 + .oo zyxwvuts 0956-716X(95)00325-8 EFFECT OF SOLUTION TREATMENT ON THE STRESS RUPTURE PROPERTY OF MA ODS Ni-BASE SUPERALLOY AT 760°C Lee Ju Park, Young Gil Kim and Soon Hyung Hong Department of Materials Science and Engineering, Korea Advanced Institute of Science & Technology, Taejon, Korea R. M. Haeberle and A. S. Watwe INCO Alloys International, INC., Huntington, WV, U. S. A. (Received March 22,1995) (Revised May 22,1995) Introduction The strengthening of mechanically alloyed (MA) oxide dispersion strengthened (ODS) Ni-base superalloys is obtained through the precipitation hardening by a Ni,(Al, Ti), which is known as y’ phase, at the intermediate temperature region of 760-45O”C. The y’ precipitates are ordered FCC (LlJ structure and are coherent with the nickel-rich y matrix having FCC structure. The size, volume traction and distribution of the y’ precipitates are sensitively related to the heat treatment for precipitation and these parameters can significantly at&& the mechanical properties of ODS Ni-base superalloys[ 11. The MA ODS N&base supemlloys in general am given three stages of heat treatments ; (1) zone annealing treatment to develop a stable coarse-grained structure suitable for high stress-rupture properties ; (2) solution heat treatment to dissolve the y ’ so that it can subsequently be precipitated ; (3) aging treatments to precipitate fine y’ carbides and bori&s at grain boundaries[2-51. The aim of this study was to investigate the effect of solution heat treatment temperature on the y’ precipitate size and stress rupture property of MA ODS Ni-base superalloy. The deformation mechanism of ODS N&base superahoy was discussed by observing the interaction between dislocations and y ’ precipitates at 760°C. Exuerimental Procedure An oxide dispemion ,s&&emd Ni-base superahoy, which is designated as Alloy 92, was prepared at INCO Alloys International Inc. The elemental powders and master alloy powders were mechanically alloyed in an attritor ball mill. The mechanically alloyed powders were packed into mild steel cans and the cans were evacuated and sealed. The sealed cans were extruded into bars with 1Scm in diameter at 1175°C with extrusion ratio of about 17:1. The nominal composition of the ODS Ni-base superalloy (Alloy 92) is listed in Table 1. 1127