Abstract: A method of manufacturing an aluminum alloy forged material from a mixture containing an aluminum scrap, an aluminum virgin metal, and an additive element includes the following steps: a heating and melting step of heating and melting the mixture, a forging step of forging the mixture after heating and melting, and an aging treatment step of performing aging treatment on a material after the forging step under a condition that an aging temperature and an aging time are as follows: (aging temperature, aging time)=within a range of a region surrounded by (185, 4), (185, 7), (200, 1), and (200, ?2/25x+8).

Abstract: A method of manufacturing an aluminum alloy forged material from a mixture containing an aluminum scrap, an aluminum virgin metal, and an additive element includes the following steps: a heating and melting step of heating and melting the mixture, a forging step of forging the mixture after heating and melting, and an aging treatment step of performing aging treatment on a material after the forging step under a condition that an aging temperature and an aging time are as follows: (aging temperature, aging time)=within a range of a region surrounded by (185, 4), (185, 7), (200, 1), and (200, ?2/25x+8).

Abstract: An outer cover member of a plastic rocker cover has a top wall, a peripheral wall and a partition wall cooperating with the top wall and the peripheral wall to define therebetween an oil-gas separating chamber. The peripheral wall has a plurality of flanged portions at which the rocker cover is to be bolted to a cylinder head. The outer cover member further has a plurality of resiliently deformable buffer walls integral with a top wall of the outer cover member and depending therefrom so as to be spaced inward from the flanged peripheral wall portions. The partition member is secured to lower ends of the buffer walls so that oil-gas separating chamber is partly defined by the buffer walls. The buffer walls are resiliently deformable to absorb thermal expansion and contraction of the partition member.