Keh-Minn Chang

Boron extended solubility and strengthening potency in rapidly solidified Ni3Al

Abstract The strengthening of the intermetallic compound Ni3Al by boron addition has been investigated via the rapid solidification technique of melt spinning. Using X-ray diffraction, differential thermal analysis and transmission electron microscopy it is shown that by rapid solidification up to 1.5 at.% boron can be held in solution in the aluminide without formation of boride. The lattice parameter results further show that the boron atoms in solution tend to occupy the interstitial sites, generate large lattice strain, and thereby strengthen the Ni3Al substantially. For example, addition of 1 at.% boron increases the room temperature yield strength of rapidly solidified Ni3Al from ∼480to∼750MPa. This represents a strengthening potency significantly larger than that of substitutional solutes.

Ductility in boron-doped, nickel-base L12 alloys processed by rapid solidification

Etude de la ductilite dans les composes intermetalliques de type Ni 3 X (ou X=Al, Ga, Si, Ge) de structure ordonnee L1 2 en fonction de la teneur en bore (0,1 a 1% at.)

Carbon effects in rapidly solidified Ni 3 Al

The effect of carbon on the mechanical properties of ordered, face-center-cubic Ni 3 Al has been studied. It has been found that carbon provides no ductihzation to the intermetallic compound, but exerts a large solid solution strengthening effect. The strengthening rate measured is Δσ y /ΔC∼0.5 G per atom percent carbon, where G is the Ni 3 Al shear modulus. Auger analysis and lattice parameter measurements were also carried out. The results are discussed with respect to the nature of carbon in grain boundary regions and in the bulk.

Tensile and impact properties of directionally solidified Fe-40AI intermetallic

This paper reports the results of uniaxial tensile and Charpy V-notch impact tests for directionally solidified Fe-40Al intermetallic across the «transition» temperature (20-800 o C)

CRYOGENIC PROPERTIES OF A P/M Ni3Al-B ALLOY

Polycrystalline Ni/sub 3/Al-based intermetallic alloys have overcome their room temperature brittleness problem with a small amount or boron addition. Because of their unique strength-temperature relationship and good oxidation resistance at high temperatures, research efforts have been concentrated extensively on structural applications at elevated temperatures. In this paper the authors show that ductile Ni/sub 3/Al-B alloys also exhibit remarkable mechanical properties at cryogenic temperatures.

Property Comparison of Melt-Spun Ribbons and Consolidated Powders of Ni 3 A1-B

Ductile intermetallic Ni 3 Al-B alloys have been processed through three rapid solidification techniques: melt spinning, gas atomization, and plasma deposition. Different thermal treatment was required for each rapidly solidified product to form samples for mechanical evaluation. Melt-spun ribbons were tested in ribbon form in the as-cast or annealed conditions, while atomized powders were tested after consolidation by hot isostatic pressing (HIP) or low pressure plasma deposition. Alloy strength, as well as tensile ductility, was found to depend strongly on processing technique, thermal treatment, sample geometry, and most importantly, alloy chemistry. Microstructural and fractographic observations indicate that grain boundary brittleness caused by material processing history plays the major role in determining the alloys mechanical behavior.