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.
Roles of β phase in the corrosion process of AZ91D magnesium alloy
For better understanding of the roles of beta phase in the corrosion processes of AZ91D alloy, corrosion behavior of a cast (alpha + beta phase) and a homogenized (beta phase) AZ91D alloy was investigated in NaCl aqueous solution by gas collection and electrochemical measurements. According to the hydrogen evolution properties during corrosion, two different types of corrosion tend might be differentiated. For type I, hydrogen diffused into alloy, which evoked the decreasing of hydrogen evolution rate (HER) and the weakening of negative difference effect (NDE). For type II, in the corrosion process, hydrogen in the alloys diffused into the product film (P-type semiconductor), which suggested that hydrogen entering the film would be ionized. The generated electrons during ionization decreased the concentration of vacancies in the valence band of the product films, indicating an improvement of corrosion resistance of AZ91D alloy. (c) 2005 Elsevier Ltd. All rights reserved.
Wood Microbiology: Decay and Its Prevention
Introductory text on the principles of decay and discoloration processes in wood, with emphasis on the major fungal damages which may develop during the growth, storage, and use of wood. The characteristics, detection, effects, and control of microbial attacks are stressed. Provides a synthesis of the current literature on wood microbiology, a rapidly expanding field of study. (Abstractor's note: This is an important resource for conservation researchers studying the decay of wood in art and architecture.) The following is a list of chapter headings: 1) Introduction to wood microbiology; 2) Wood deterioration agents; 3) Characteristics and classification of fungi and bacteria; 4) Factors affecting the growth and survival of fungi in wood (fungal ecology); 5) Fungal metabolism in relation to wood decay; 6) The decay setting: some structural, chemical, and moisture features of wood in relation to decay development; 7) General features, recognition, and anatomical aspects of wood decay; 8) Chemical changes in wood caused by decay fungi; 9) Ultrastructural features of wood decay; 10) Changes caused by decay fungi in the strength and physical properties of wood; 11) Colonization and microbial interactions in wood decay; 12) Decays originating in the stems of living trees; 13) Biodeterioration of stored wood and its control; 14) Wood stains and discolorations; 15) Decay problems associated with some major uses of wood products; 16) Detection of internal decay; 17) Paint mildew and related degradative problems; 18) Natural decay resistance (wood durability); 19) Chemical protection of wood (wood preservation); and 20) Some trends in wood microbiology research and a new emphasis (biotechnology). -- AATA