CRYSTAL ORIENTATIONS AND REFLECTIVE PROPERTIES OF THE COARSE-GRAINED ALUMINUM-ALLOY PLATE FOR INTERIOR MATERIALS

The aluminum alloy (JIS-A1070: 99.7%Al) plate showing a large grain pa tterns is used as an interior material. We investigated the relationsh ip between the optical properties to surface morphology and crystal or ientations of this type of aluminum plate. The annealed sample having coarsened grains (5-20 mm diameter) was etched with a mixture of sulfu ric acid and hydrochloric acid. The crystals are classified into two t ypes from the reflective properties by the measurement of regular refl ectance for each crystal: one is the crystal which has smooth surface and shows high regular reflectance. The other one is the crystal which has similar to 2 mu m high jagged surfaces such as a wavy pattern: th e regular reflectance is less than a few % on the surface of the cryst al. (The main reflective face of this type of crystal should be the ob lique plane of jag.) The former type of crystal is named ''type A'' an d the latter is ''type B'' provisionally. Some of these types of cryst als were cut out and their crystal orientations were measured by using an Xray diffractometer having the S-axis goniometer. As a result, typ e A crystals have the (310) or (100) plane and all of type B have the (110) plane, which are parallel or inclined less than 10 degrees to th e plate surface. Furthermore, the longish direction of wavy jag is vir tually parallel to the [100] direction of type B crystal. Since the in cident light on type B crystal should be mainly reflected on the obliq ue plane, the brilliancy of each type B crystal depends on the directi on of the wavy pattern, namely on the [100] direction. From these resu lts, it is important for a interior material to have a properly disper sed direction of [100] with a view to showing a multiform reflection. Accordingly, the materials composed of strongly oriented crystals are found to be unsuitable for interior materials.