Transmission electron microscopy and measurements of hardness and electrical resistivity were carried out on the alloy aged at various temperatures 40 to 300°C. This alloy follows a similar course of precipitation as common Al-Cu-Mg alloys. The pre-precipitation zones G. P. B. are considerably formable in the early stage of aging at temperatures bellow 200°C. The forming rate of the G. P. B. zones increases with concentration of the solutes in the alloys having a same ratio of Cu: Mg. High density of dislocation loops and helices are found in the stages of the G. P. B. zones formation at 120°C or bellow. The S' phase precipitates and grows in the distored lath form at aging temperatures above 120°C forming corrugated composite sheets and chevron markings as in the common Al-Cu-Mg alloys. The S phase precipitates and grows in the lath form at elevated temperatures above 250°C. The growth rate of it is considerably lowered in the prolonged aging at 250°C for more than 10⁴min.

View full abstract

Studies were carried out to clarify the effects of several gases mixed to argon gas on appearance of bead, shape and depth of penetration, wettability of deposited metal, porosities in weld metal, and microstructure of weld metal in MIG welding of A5083 alloy. Mixing several volume % of oxygen gas to argon gas is effective for increasing the depth of penetration, improving wettability, and decreasing porosities. Mixing nitrogen gas leads to little improvement in in depth of penetration or wettability though it serves to minimize blow holes but not to the same extent as mixing oxygen gas. Mixing hydrogen gas to argon permits similar properties as those brought on pure argon gas except increasing porosities. Both the argon-carbon dioxide and argon-oxygen mixtures have similar consequences.

View full abstract

Young's modulus of a typical solution-hardened alloy Al-5.6at%Mg was measured at temperatures from 20° to 450°C by the resonant frequency method. The temperature dependence of Young's modulus of the alloy is nearly equal to that of 99.99% pure aluminum.

View full abstract

Orthogonal cutting tests and fretting tests were carried out by using such extreme pressure fluids as carbon tetrachloride, tricresyl phosphate and tri-n-butyl phosphate and a practical cutting fluid lard-kerosene mixture. The specimens were completely dipped in the fluids or the fluids were supplied over the surface of the specimen. All cutting fluids play roles for lubrication on the rear surface of chips. The fretting tests shown adaptability of the extreme pressure fluids for cutting the 7075-T4 alloy. Tricresyl phosphate (aryl series) and tri-n-butyl phosphate (alkyl series) of the phospholic esters have lubricating actions different from each other.

View full abstract

A dry wear test was made on the Al-1.53.5%Mg alloys unidirectionally solidified. The wear characteristics prominently depends on the solidified structure at low friction speeds. The equi-axial structure has a wear resistance superior than columnar structure. The fact is closely related to the impact strength. The alloys containing more amounts of Mg show greater wear resistance. The wear mechanism is independent to the structures and Mg contents in the alloys. Considerable amounts of iron tranfer onto the sliding surfaces of the alloys at an initial stage of low speed friction easily forming ferrous oxides. A part of the friction layer is fused at a high friction speed which results is decrease in wear loss. When considerable metal transfer occurs at higher friction speeds, however, heavy adhesion and fusion lead to increase in wear loss.

View full abstract