Papers by Author: Carl Blais

Abstract: The automotive industry applies pressure on the PM industry to produce components with superior mechanical properties at minimum cost. In this regard, sinter-hardenable powders are particularly well suited since they allow direct quenching of components at the end of the sintering cycle, thus eliminating the extra steps required for heat treating. This paper presents the results of the modeling of the influence of admixing and/or prealloying on the optimization of compressibility and hardenability of sinter-hardenable steel powders. A first design of experiments (DOE) was used to optimize the chemical composition and to study the interactions between prealloyed elements (Nickel, Chromium, Molybdenum and Manganese) and admixed elements (Nickel, Chromium, Manganese and Copper) on hardenability and compressibility. A second DOE was generated based on the results obtained in the first series. Results show that among all of the examined alloying elements, only prealloyed nickel, chromium and molybdenum had a significant effect on compressibility and hardenability. Moreover, within the range of concentrations under study, the optimum sinter-hardenable powder had the following (prealloyed) chemistry: 1.5 wt-% Ni, 0.55 wt-% Cr and 1.25 wt-% Mo.

Abstract: Utilization of aluminium-lithium alloys in aerospace applications requires an understanding of how processing and product geometry impact their microstructure, crystallographic texture and mechanical properties. In this paper, the effect of various microstructural features as well as deformation textures on the static mechanical properties of Al-Li extruded components has been investigated. These relationships are discussed with regard to two 2099-T83 extruded sections, i.e. a cylindrical extrusion and an integrally stiffened panel (ISP). The ISP typically shows an unrecrystallized microstructure with varying texture depending on the location along its cross section while the cylindrical extrusions present a strong fibre texture. The anisotropy is noticeable in tensile and compressive tests for both types of extrusions.

Abstract: An integrally stiffened panel (ISP) made from extruded 2099-T83 Al-Li alloy was subjected to fatigue loadings to investigate the influence of both the local texture and grain structure on fatigue crack propagation (FCP) behavior. The microstructure was mainly unrecrystallized. Grains were mostly layered in the web and fibrous in the other locations. Fiber texture components were present in the stiffener locations, and a rolling-type texture in the web. Resistance to FCP decreases as the local aspect ratio increases. Changes in FCP rates in the web, stiffener base and stiffener web were consistent with the microstructural features and texture. The stiffener cap with a strong fiber texture similar to that of the stiffener base exhibited a lower resistance to FCP, suggesting that the influence of the texture is convoluted in the stiffener cap by the markedly different grain structure. Therefore, FCP behavior in this alloy appears to be governed by both texture and grain structure.