Strengthening of a thin austenitic stainless steel coil by cold wavy rolling with no magnetic and dimensional changes

A comparison of the effects of wavy rolling and cold rolling on microstructure variation, phase evolution, tensile and magnetic properties of a thin coil of Fe-18.47Cr-8.10Ni-0.94Mn austenitic stainless steel was made at room temperature. Wavy rolling led to strengthening with no change in magnetic property and thickness, unlike the conventional cold rolling that changed all these properties by deformation induced martensitic transformation, in addition to substructure evolution. The yield strength of 413MPa and magnetic saturation 3.7 emu/g under mill-annealed condition increased, respectively, to 1208MPa and 11.8 emu/g, upon four cycles of wavy rolling. While the maximum yield strength of 1790MPa could be achieved by combining this stage of four cycles of wavy rolling with subsequent 50% conventional cold rolling, the magnetic saturation increased to 73.3 emu/g by deformation induced martensitic transformation caused by the latter

On the evaluation of stability of rare earth oxides as face coats for investment casting of titanium

Attempts have been made to evaluate the thermal stability of rare earth oxide face coats against liquid titanium. Determination of microhardness profiles and concentration profiles of oxygen and metallic constituents of oxide in investment cast titanium rods has allowed grActation of relative stability of rare earth oxides. The relative stability of evaluated oxides in the order of increasing stability follows the sequence CeO2 — ZrO2 — Gd2O3 — didymium oxide — Sm2O3 —Nd2O3 — Y2O3. The grading does not follow the free energy data of the formation of these oxides. A better correlation with the experimental observations is obtained when the solubility of the metallic species in titanium is also taken into consideration

Evaluation of the reactivity of titanium with mould materials during casting

A methodology for evaluating the reactivity of titanium with mould materials during casting has been developed. Microhardness profiles and analysis of oxygen contamination have provided an index for evaluation of the reactivity of titanium. Microhardness profile delineates two distinct regions, one of which is characterised by a low value of hardness which is invariant with distance. The reaction products are uniformly distributed in the metal in this region. The second is characterised by a sharp decrease in microhardness with distance from the metal-mould interface. It represents a diffusion zone for solutes that dissolve into titanium from the mould. The qualitative profiles for contaminants determined by scanning electron probe microanalyser and secondary ion mass spectroscopy in the as-cast titanium were found to be similar to that of microhardness, implying that microhardness can be considered as an index of the contamination resulting from metal-mould reaction

Reduction In Metal-Mold Reactivity In Titanium Castings Through The Use Of Sodium Aluminate As Binder In Zircon Sand Molds

The present work is aimed at evaluating an alternative moulding system, namely, sodium aluminate bonded zircon sand mould and assess its suitability in relation to the much studied sodium silicate bonded zircon sand moulding system. It is described in the study presented here that with regard to metal - mould reaction, sodium aluminate bonded zircon sand mould system is a superior viable system as compared to sodium silicate bonded zircon moulding system at mould firing temperatures of 873 - 1473 K

Microstructural changes induced by ternary additions in a hypo-eutectic titanium-silicon alloy

Hypo-eutectic Ti-6.5 wt % Si alloy modified by separate additions of misch metal and low surface tension elements (Na, Sr, Se and Bi) has been examined by microscopic study and thermal analysis. Addition of third element led to modification of microstructure with apparently no significant enhancement of tensile ductility, with the exception of bismuth. Bismuth enhanced the ductility of the alloy by a factor of two and elastic-plastic fracture toughness to 9 MPa m–1/2 from a value of almost zero. The improved ductility of bismuth modified alloy is attributed to the reduced interconnectivity of the eutectic suicide, absence of significant suicide precipitation in the eutectic region and increase in the volume fraction of uniformly distributed dendrites. These changes are accompanied by a decrease in the temperature of eutectic solidification

Metal mould reactions during casting of titanium in zircon sand moulds

Metal-mold reaction during Ti casting in zircon sand molds has been studied using scanning electron microscope, energy and wave length dispersive analysis of X-rays, X-ray diffraction, microhardness measurements, and chemical analysis. Experimental results suggest that oxides from the mold are not fully leached out by liquid Ti, but oxygen is preferentially transferred to liquid Ti, leaving behind metallic constituents in the mold as lower oxides or intermetallics of Ti. The electron microprobe analysis has revealed the depth profile of contaminants from the mold into the cast Ti metal. The elements Si, Zr and O were found to have diffused to a considerable distance within the Ti metals. A possible mechanism has now been evolved in regard to the reactions that occur during casting of Ti in zircon sand molds

Hot ductility of an electroslag crucible melted age hardenable Cu-Cr alloy

The electroslag crucible melting process (ESCM), developed on the well established principles of electroslag refining was used to cast age hardening Cu-0.5%Cr alloys using copper scrap. The alloys exhibited superior room temperature tensile strength and ductility compared with conventional wrought material. An important aspect of the ESCM process is that there is considerable chemical refinement of the alloy with respect to both oxygen and sulphur due to reactions inherent in the process. This results in improved hot ductility (to the extent of similar to 45%) of the ESCM alloy compared with the material produced by the vacuum melting process. (C) 1997 The Institute of Materials