A procedure for accurately and quantitatively evaluating the resistance of Rene 41 to strain-age cracking during postwelding heat treatment is reported. The procedure requires only conventional laboratory equipment and welding facilities are not necessary.It is now possible to determine the resistance of heats of Rene 41 to strain-age cracking prior to their introduction into production lines, and to evaluate the effects of material and process variables on strain-age cracking.The mechanical properties of welds, parent-metal, and simulated weld heat-affected zones were studied. It was found that resistance to strain-age cracking was related to the ductility of each heat at elevated temperatures.To perform the test, tensile specimens were first solution annealed and water quenched, and the heating rate to the test temperature was held between specified limits. In the solution annealed condition, the higher the ductility at temperatures from 1500 to 1650 F, the greater the resistance to strain-age cracking. However, over this interval of temperatures the ductilities of all heats were in the range of only 1 to 4%, and the elongation at fracture had to be precisely determined.It was concluded that some form of embrittlement occurs and, while all heats of Rene 41 are embrittled, the severity, and hence the resistance to strainage cracking differs from heat to heat. Exposure of the alloy to temperatures close to the melting point, as occurs in the heat-affected zone of a weld, reduces ductility, but is not necessary for embrittlement. Strain-age cracking appears to be related to the physical metallurgy of Rene 41 in general, and not just to the microstructure of the heataffected zone. Heat to heat variations in strength and resistance to relaxation were not found to be related to differences in resistance to strain-age cracking.