Observations on strengthening and oxidation behavior of a dispersion hardened Fe-Cr-Base alloy prepared by mechanical al
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Observations on Strengthening and Oxidation Behavior of a Dispersion Hardened Fe-Cr-Base Alloy Prepared by Mechanical Alloying
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I. G. WRIGHT AND B. A. WILCOX
In the last decade, there has been a large r e s e a r c h effort on dispersion-strengthened nickel alloys, and | I I I today there are available commercial alloys of thoriIO 20 w 0 :E ated nickel, thoriated nickel-20 pct chromium, and OIMENSIONLESS HALF THICKNESS , hL/K dispersion-strengthened superalloys containing y ' as Fig. 4--Curve for determining quench speeds of sheet metal well as dispersed oxide particles. Considerably less specimens. The two sets of data (e and A) are plotted separ e s e a r c h has been done on dispersion-hardened iron rately, each plotted using the average h value for that set. No adjustment is made for the variation of probe dimension alloys, although previous studies have shown that oxide in the direction of fluid flow. dispersion strengthening of iron alloys is a viable concept. z-z1 the fluid from a portion of the probe surface. Due to Earlier work used more traditional powder p r e p a r a the finite width of a probe and the radius of the circle tion methods, such as ball milling, co-precipitation, of motion, there is as much as a three and one half colloidal mixing, and oxidation-reduction of iron comdegree angle of incidence for fluid flow near the probe pounds. However, the ~oioneering work of Schafer, edges, even with the best possible positioning. C e r Quattnetz and Weeton z on attritor milling culminating tainly the quenching speed is reduced noticably if the in the development of "mechanical alloying" by Benspecimen or probe is not tangent to the circle of mojamin zs has provided r e s e a r c h e r s with a new method tion. of preparing dispersion-hardened alloys. Mechanical Fig. 4 may now be used to determine the quench alloying involves charging an attritor mill with hard speed of a thin sheet metal specimen. The thermal balls and powders of the base metal, alloying compodfffusivtty and thermal conductivity of the material nents, and particles of the dispersoid. The milling is must be known. The dimensionless half thickness hL/K done with no c a r r i e r fluid and the action of the mill is then found using a heat transfer coefficient from causes the powders to weld to the balls. Repeated Table II. The dimensionless quench speed Q can now welding and breaking away of the powder from the balls be found from the curve of Fig. 4. Finally, the quench "mechanically" incorporates the dispersoid into the speed is q. = (a/LZ) (T.-T=) Q. F o r thin samples with metal powder. The powder itself is not completely hohL/K < 1, Zsurface controli~d~ heat flow can be assumed mogeneous, but after thermomechanical processing to and then qi = (Ti - Tb)hrv/KL" This procedure is valid bar or sheet the composition is very uniform.
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