No abstract

Three unique high resolution experimental arrangements for nondestructive strain measurements which are based on neutron Bragg diffraction optics with cylindrically bent perfect crystals are reviewed. Using focusing in momentum and real space thgfe techgiques yield Ad/d (d-lattice spacing) resolution of 10-10-and considerably higher luminosity in comparison with the current dedicated instruments. They permit measurements not only macrostrain components resulting in angular shifts of diffraction peaks but also of microstrains by means of profilebroadening analysis.

No abstract

The CMA-powder and the Al-CMA composite (CMA = Al73Mn21Fe6) have been studied with the intention to characterize the influence of selected technological procedures (milling for 80 h, extrusion at 400 • C under 500 MPa, compaction at 550 • C for 0.5 h, and annealing at 550 • C for respective 0.25 and 0.5 h) on the phase evolution inside CMA-areas and at Al/CMA interfaces. In the investigation X-ray diffraction and scanning electron microscopy including energy dispersive X-ray spectroscopy were used. It was shown that CMA-powder consisting of T(HT) + γ2 became totally amorphous after 80 h of milling. During extrusion, compaction, and annealing of the Al-CMA composite, the originally amorphous CMA particles were found to transform into crystalline phases at the assistance of aluminium diffusion towards the CMA-area. At the Al/CMA interfaces on the CMA side, IMC-areas (IMC = intermetallic compound) were formed consisting of Al6(Mn, Fe). T(LT) + Al4(Mn, Fe) + Al6(Mn, Fe) phases were identified in the CMA-areas after the annealing of the Al-CMA composite for 0.5 h at 550 • C. K e y w o r d s : metal-matrix composites, interfaces, scanning electron microscopy, energy dispersive X-ray spectroscopy, extrusion, annealing

Article presents results on the analysis of secondary phases formed in the medium-term static isothermal ageing welding joints of a SUPER 304H (675 • C/2 × 10 4 h). The investigations of the precipitates were focused on the occurrence of σ-phase because its formation leads to significant deterioration of mechanical properties. The microstructure was investigated on microscopic level by scanning/transmission electron microscopy. The distribution and quantification of brittle σ-phase were studied on macroscopic level by color etching method using light optical microscopy. The effect of microstructural changes (σ-phase formation) on the impact strength of an aged base material was investigated. For comparison impact tests on received state material were also performed. The results showed that long-term ageing led to the significant reduction of impact strength as a result of the formation of the σ-phase. It was found that the σ-phase distribution is influenced by welding process. The influence of brittle σ-phase on long-term durability of the degraded steel regarding its insufficient impact strength has been discussed.