The Effect of Heat Treatment on the Fracture Toughness and Subcritical Crack Growth Characteristics of a 350-Grade Maraging
The heat treatment response of a 350-grade maraginf steel, with the nominal composition 18.5 Ni, 12 Co. 4.6 Mo, 1.4 Ti, balance le. has been determined in billet and bar form. When ■ged at temperatures below 90(rF, the material was very susceptible to subcritica! crack growth, and premature brittle Iracture occurred in unnotched tension specimens loaded at a slow strain rate in laboratory air. Fracture mechanics was used to interpret this behavior. The introduction of reverted austenite signiticantly decreased the strength level but had little effect on Iracture toughness. The resistance to brittle Iracture of this material is contrasted with that ot high-strength steels currently used by the airplane industry. INTRODUCTION F'he continuing demand lor ultra-high-strength steels prompted the recent development ol two 3S0-grade maraging steels. The development and properties of one alloy nominal composition P.5 Ni. i:.5Co. .VK Mo. 1.7 Ti. 0.15 Al. balance le were recently described ( I ). Vasco Metals, a subsidiary of I eledyne. Inc.. introduced a second alloy that is lower in titanium than the first to avoid segregation problems and has slightly higher nickel and molybdenum contents. Fn this paper, the effect of heat treatment on the fracture toughness and subcritical crack growth resistance of this second alloy is described.
The physical metallurgy of maraging steels
AbstractMaraging steels are a class of high-strength steels characterised by very low carbon contents and the use of substitutional elements to produce age-hardening in iron–nickel martensites. The term 'maraging' was coined from a combination of martensite and age-hardening.
Electrochemical detection of copper(II) at a gold electrode modified with a self-assembled monolayer of penicillamine
A penicillamine (PCA) self-assembled monolayer (SAM) was prepared on a gold electrode. It has been found that the modified electrode exhibited a selective response to copper ions. As demonstrated by cyclic voltammetric experiments, the SAM-based electrode showed an attractive ability to preconcentrate efficiently traces of copper(II) from solutions. Under optimum conditions, the anodic peak current was proportional to the concentration of Cu(II) in the range from 8.0 × 10−7 to 1.0 × 10−4 M with a detection limit of 4.0 × 10−7 M. Moreover, this modified gold electrode is also characterized by excellent repeatability, showing a relative standard deviation of 3.2% for nine successive measurements of 1.0 × 10−5 M Cu(II). The PCA/Au SAM gold electrode was used for the determination of Cu(II) in a tap water sample and the results showed a good agreement with the data obtained by atomic emission spectrometry.