Investigation of Fracture Mechanisms, Thermal Stability and Hot-Strength Properties of Controlled Polyphase Alloys

摘要

The effect of reinforcement size on the room temperature tensile strength of A1-A13Ni and A1-CuA12 unidirectionally solidified composites was investigated. Within the range of solidification rates studied (2 to 11 cm/hr), the reinforcement size varied by a factor of two times and no effect of reinforcement size on strength was noted. It was found that the variation of tensile strength with temperature closely parallels the behavior noted for S.A.P. A preliminary investigation of the creep behavior of A1-A13Ni indicates that the strain rate during the second stage of creep is comparable to that of S.A.P. although the total strain is greater. The preferred crystallography for each system persisted after long times at elevated temperatures. The microstructure of each system was changed significantly only by heat treatment at relatively high temperatures. The stability of the microstructure at elevated temperature varied inversely with the solidification rate. (Author)