Influence of solid-solution treatment on corrosion performance of cast AM50 magnesium alloy
It was investigated by quenching the AM50 magnesium alloy test samples in water after T4 treating (420 °C) for 24 h. Then both kinds of the test bars were immersed in 3.5 wt. % NaCl saturation Mg (OH) 2 aqueous solution for 0, 24 and 72 h. Then tensile tests were taken. The microstructure of the samples was analyzed by scanning electronic microscope and X-ray diffraction. The results show that though solid-solution treatment improved the corrosion residual strength of the cast AM50 magnesium alloy for 24h, the deeper corrosion pits developed on the heat-treatment samples on 72h caused more drop of the strength compare to the untreated samples. The solid-solution treatment and the extreme depth theoretical of corrosion pits effect together to the corrosion residual strength.
Understanding Magnesium Corrosion—A Framework for Improved Alloy Performance
The purpose of this paper is to provide a succinct but nevertheless complete mechanistic overview of the various types of magnesium corrosion. The understanding of the corrosion processes of magnesium alloys builds upon our understanding of the corrosion of pure magnesium. This provides an understanding of the types of corrosion exhibited by magnesium alloys, and also of the environmental factors of most importance. This deep understanding is required as a foundation if we are to produce magnesium alloys much more resistant to corrosion than the present alloys. Much has already been achieved, but there is vast scope for improvement. This present analysis can provide a foundation and a theoretical framework for further, much needed research. There is still vast scope both for better fundamental understanding of corrosion processes, engineering usage of magnesium, and also on the corrosion protection of magnesium alloys in service.
Traceability strategy for gear-pitch-measuring instruments: development and calibration of a multiball artifact
There is a strong demand to ensure the traceability of gear-measuring instruments (GMIs). We propose a multiball artifact (MBA) for the evaluation of pitch-measuring accuracy. The aim of the MBA is to transfer the minimum uncertainty from a calibrated value at the National Metrology Institute of Japan (NMIJ) to a measured value of GMIs at a shop floor. The MBA is composed of equally spaced high-accuracy balls around an axis. The pitch-measuring accuracy of GMIs is evaluated by measuring the angular pitch deviation of the balls instead of the angular pitch deviation of a gear. We calibrated the angular pitch deviation using a coordinate measuring instrument (CMM) at the NMIJ and adapting a multiple-orientation technique. We proposed a calibration strategy of the angular pitch deviation. The calibration value of the pitch deviation for the MBA at the NMIJ was obtained with a measurement uncertainty (U95) of 0.2 µm. We evaluated the pitch-measuring accuracy of a GMI using the calibrated MBA. Each value of U95 for the cumulative and single pitch deviations for the left and right flanks was less than or equal to 0.5 µm. The small uncertainty was transferred from the NMIJ to the GMI.