HIGH-TEMPERATURE DEFORMATION OF SINGLE-CRYSTAL YTTRIUM-ALUMINUM-GARNET (YAG)

Single crystals of Y3Al5O12 (YAG) were deformed in air along the [135] direction at 1635 degrees and 1785 degrees C using constant strain ra te compression, The primary creep region, characterized by ''strain so ftening,'' persists to at least 4% plastic strain before steady-state behavior is achieved. Creep rates, stress exponents, and activation en ergies were compared to literature results and suggest the operation o f multiple mechanisms over the range of conditions studied, Slip trace analysis confirmed that {110}[(1) over bar 11] was the primary slip s ystem. Slip on both highly stressed (211) and ''anomalous'' (1(1) over bar2$) planes was also observed, Dislocation structures mere analyzed by transmission electron microscopy and consisted of networks and coa rse loops. These results are discussed in terms of asymmetric slip geo metry classically observed in body-centered cubic (BCC) metals.