The coarsening of γ'precipitates along the direction perpendicular to the externally applied stress axis was investigated for [001]-oriented single crystal superalloy CMSX-4 under 1253 K, 350 MPa tensile creep test. It is found that the portion of edge areas of cuboidal γ'precipitates grew preferentially and the γ-γ'interfaces progressed concavely,which was followed by the enclosure of the adjacent vertical matrix channels (parallel to [001]), and the linked γ'precipitates gradually exhauseted the retained vertical channels and finally developed into rafted plates. The directional coarsening led to a decrease in the size of γ'precipitates in the [001] direction and to an increase in the width of the horizontal matrix channels (perpendicular to[001]). The specific growth manner of the γ'precipitates and the characteristics of the morphological evolution of the two coherent phases in the tested samples are discussed.

The interfacial microstructures and composition alteration of hot-rolled 316L/ 16MnR composite plate have been observed by TEM,SEM and X-ray energy spcetrum techniques. The hot-rolled composite is a diffusion process, and the diffusion range of the elements is about 50 μm. The side of steel next to interface consists of ferrite, small amount of martensite and pearlite, while the side of the stainless steel consists of the elongated and recrystallized austenite graius. The continuously precipitated carbide M23C6 has been observed along the austenite boundaries. The microstructure at the interfaceshows the coexistence of ferrite, martensite and austenite

The morphology and distribution of carbides in a directionally solidified cobalt-base superalloy have been studied. When the silidification rate,ν, was 7 mm/min the alloy contatined a maximum content of carbides. The carbide content increases as the increasing in ν up to 7 mm/min, and then, it decreases with the increase in νover 7mm/min, and the size of carbides reduces sharply. Both content and size of carbides increase nomotonously with the distance apart from the chilled plate.