Phenomenon of reversion after ageing in magnesium alloys with gadolinium and samarium

The parameters of reversion after hardening ageing of magnesium alloys containing two rare-earth metals: gadolinium (yttrium group) and samarium (cerium group) were determined at various ratios of their contents. The reversion was observed at short annealing at 250 and 300 °С beginning with 5 minutes after preliminary ageing at 200 °С up to maximum hardening and consisted of significant softening of the alloys then. Measurements of the electrical resistance indicated, that during softening the reverse dissolution of the rare-earth metals in magnesium-base solid solution takes place with diminution of the hardening particles quantity, precipitated during ageing before The reverse dissolution of the rare-earth metals into solid magnesium increases with elevating annealing temperature after ageing from 250 to 300 °С and with increase of the gadolinium to samarium ratio in the alloys.

Effect of Melt-Casting Temperature on Bonding Zone of CuNiMnFe30CrMnSi Integral Material

The effect of melt-casting temperature on the microstructure and properties of transition interlayer for CuNiMnFe/30CrMnSi material was investigated in vacuum condition. The results show that the thickness of the transition layer and its bond strength increase, and then decrease with increasing temperature. At 1130 , the intermediate transition layer has the largest width, which is 132μm, and the tensile strength can reach up to 1322Mpa. In the intermediate transition layer, mutual diffusion occurs among these alloying elements. These elements, such as Cu, Ni and Mn, diffuse into 30CrMnSi and results in the formation of Fe base solid solution, and no harmful brittle phases are produced in the proximity of bonding interface, thus it has a good metallurgical bonding for the two materials.

The Study on the Dispersants and Structures of Ni-P-α-Al2O3 Composite Electroless Plating Coating

Dispersants are selected and optimized by determining the height of emulsion in the colorimetric cylinder after standing in order to ensure the homogeneity of the powder and the stability of electroless plating solution. Experimental results show that non-ionic surfactants such as PEG6000,PEG10000,OP-10 have stronger emulsifying ability to α-Al2O3 powder in ordinary condition and IW has more stability at 80~90°C. The optimum conditions are suggested as PEG6000 8g, IW 0.95g and ethanol 3mL per 50mL solution. Moreover, this composite electrolessplating solution is stable for seven days under 90°C. Therefore it has more dispersing ability. The SEM images show that the powder in the coating is homogeneous. The electroless plating coating consists of α-Al2O3 and amorphous Ni-P that will change into crystal Ni3P and Ni-base solid solution after heat treatment at 400°C for one hour, the α-Al2O3 powders are dispersed evenly in the nickel matrix.

Microstructure and Performance Analysis of Cr3C2-25%NiCr Coating Prepared by Plasma Spraying Process

Cr3C2-NiCr compound coating was acquired on 20 steel substrate by plasma spraying process. The microstructure of the coating is dense with low porosity. Carbide lamellartiy inlays into the nickel-base solid solution in the coating. Main phases of the coating are Cr3C2, Cr23C6, Cr7C3 and nickel-base solid solution, etc. Average microhardness of the coating is about HV0.1756.9. Microhardness of some ceramic phases in the coating is as high as HV0.11113, which helps to the improving of wear resistance of the coating. The wear-resisting property of the coating is good under grain-abrasion condition and excellent under lubricated wear condition.

The Fine Microstructure of a Mechanically Alloyed Oxide Dispersion Strengthened Solid Solution

A recent development in powder metallurgy technology, known as mechanical alloying (1), can find applications in alloys which cannot be manufactured by conventional processes, due to high melting temperatures, chemical incompatibility of constituents in the melt, or high reactivity. The process has been utilized in the production of a nickel-base superalloy and a nickel-base solid solution which contain dispersions of fine and inert oxide particles for high temperature strength. As part of a study of the creep and stress rupture behavior of these alloys, the as-received and crept microstructures have been examined using the transmission electron microscope. This note discusses the fine-scale microstructure of the mechanically alloyed oxide dispersion strengthened (ODS) nickel-base solid solution.The alloy has a nominal chemical composition in weight percent of Ni - 20Cr - 0.5Ti - 0.3A1 with O.6Y2O3 oxide particles.