Fabrication of High Aluminum Content Mg alloys using a Horizontal Twin Roll Caster
This study was aimed for investigating of manufacturing high aluminum content Mg alloys using a horizontal twin roll caster. Recently, weight saving has been key issues for lighter transport equipments as well as electronic componen t parts. As alternative materials to aluminum alloys, developin g magnesium alloy with higher strength has been expected. Normally hi gh Aluminum content Mg alloy has poor ductility and is difficul t to be rolled because of its high strength. However, twin roll casting pr ocess is suitable for manufacturing wrought Mg alloys because materials can be cast directly from molten metal. In this study, manufact uring of high aluminum content magnesium alloy sheet using the roll casting process has been carried out. Effects of manufactur ing parameter, such as roll velocity, pouring temperature and roll gap, on casting was investigated. A microscopic observation of the crys tals of cross section of as cast strip as well as rolled strip was conduc ted. Keywords—AZ91, AZ111, AZ121, Magnesium alloys, Twin roll casting
Twin-Roll Casting of Magnesium Alloy with High Aluminium Content
Purpose: The purpose of the work is to establish a manufacturing process and technology to facilitate the economical manufacture of high-quality magnesium sheet alloys with high aluminum contents, such as AZ61 and AZ91. The aim of the work is to establish a twin roll casting technology to facilitate the manufacture of AZ61 and AZ91 magnesium sheet alloys economically whilst maintaining high quality. Design/methodology/approach: A horizontal type twin roll caster was used to manufacture thin magnesium alloy sheets of AZ61 and AZ91. Pair of copper alloy roll and pure copper roll was used for the horizontal type twin roll caster. A closed type tundish was set to the roll caster to keep stable contact of molten magnesium with upper and lower rolls. Findings: The experiment results clarified that AZ61 and AZ91 sheets can be manufactured by twin roll casting process. The product sheet thickness in the present experiment is 2.0 to 4.5 mm for AZ91, 2.5 to 5.0mm for AZ61. Mill stiffness and a method of predicting the cast sheet’s thickness were investigated to determine the appropriate manufacturing conditions. The microstructure of AZ61 cast strips was equiaxed structure and the crystal sizes are different depending on cross section observed. The dendric and equiaxed microstructure were seen in the microstructure of AZ91 cross section. The intermetllic Mg17Al12 was seen in the grain boundary in AZ91 when roll speed was very slow. The grain size of the manufactured wrought magnesium alloys sheet was less than 10 micrometers. The obtained magnesium alloy sheet exhibited an equivalent limiting drawing ratio in a warm-drawing test. The limiting drawing ratio of AZ61 was 2.6 and 2.4 for AZ91. Research limitations/implications: The suitable roll speed was from 9m/min to 15m/min in manufacturing AZ91 and AZ61 strip using copper alloy rolls. When in use of pure copper roll, strips were cast between 6m/min and 20m/min for manufacturing AZ61 and AZ91. The superheats in the experiment were 15oC and 30oC. The cast strips should be hot rolled at 300oC. Originality/value: value In this experiment, it is clarified that AZ61, AZ91 sheets can be manufactured by twin roll casting. These cast sheet can be hot rolled and the manufacturing process by twin roll casting enable to manufacure thin magnesium sheet alloys with high aluminum contents. It has been found that the manufactured cast AZ61 and AZ91 have good formability by a warm deep drawing test.
Surface roughness monitoring by singular spectrum analysis of vibration signals
Abstract This study assessed two methods for enhanced surface roughness (Ra) monitoring based on the application of singular spectrum analysis (SSA) to vibrations signals generated in workpiece-cutting tool interaction in CNC finish turning operations i.e., the individual analysis of principal components (I-SSA), and the grouping analysis of correlated principal components (G-SSA). Singular spectrum analysis is a non-parametric technique of time series analysis that decomposes a signal into a set of independent additive time series referred to as principal components. A number of experiments with different cutting conditions were performed to assess surface roughness monitoring using both of these methods. The results show that singular spectrum analysis of vibration signal processing discriminated the frequency ranges effective for predicting surface roughness. Grouping analysis of correlated principal components (G-SSA) proved to be the most efficient method for monitoring surface roughness, with optimum prediction and reliability results at a lower analytical-computational cost. Finally, the results show that singular spectrum analysis is an ideal method for analyzing vibration signals applied to the on-line monitoring of surface roughness.