Fig. 1 Sampling positions from the ingot. Table 2 Chemical compositions of base metal (%) Fig. 2 (unit: mm) Shape and size of fatigue test specimen. T

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1 Friction welding of ADC 12 aluminum alloy diecastings Kazuyoshi KATO* and Hiroshi TOKISUE* Both squeeze and gravity castings of ADC 12 aluminum alloy were friction-welded, using a brake type welding machine. Mechanical properties and microstructures of the friction welded joints were investigated. The cast structures are pressed forward to outside along the flux of burr in the heat affected zone by axial pressure, while they disappear near the weld interface. The width of the heat affected zone of the castings is narrower than that of the wrought aluminum alloys. Hardness increases much in the weld interface, but it decreases a little in heat affected zone comparison with that of parent material. The welded joints have the same tensile strength and elongation as those of parent materials. Fracture occurs in the heat affected zone or in the parent material at a friction time of 2 to 3 sec., whiel it occurs at or near the weld interface at other friction time. The weld interface has a higher impact value than the parent material, but the place at 1 mm far from the weld interface has the same value as the latter. The fatigue strength of the welded joints of squeese castings is higher than that of parent materials. On the other hand, that of the gravity castings is slightly lower. Keywords: friction welding, ADC12 alloy, microstructure, mechanical properties, fractographs (Received August 11, 1986) Table 1 Conditions of squeeze casting College of industrial Technology, Nihon University (Narashino).

2 Fig. 1 Sampling positions from the ingot. Table 2 Chemical compositions of base metal (%) Fig. 2 (unit: mm) Shape and size of fatigue test specimen. Table 3 Mechanical properties of base metals Table 4 Welding conditions Fig. 3 Microstructures of base metals. Fig. 4 Relation between friction time and total upset.

$Fig. 5 Dependence of mechanical properties of friction welded joints on friction time. Fig. 7 Microfractographs of tensile fractured specimens.$

3 Fig. 5 Dependence of mechanical properties of friction welded joints on friction time. Fig. 7 Microfractographs of tensile fractured specimens. The friction time: 2 sec. Fig. 6 Macrofractographs of tensile fractured specimens. The friction time: 2 sec. Fig. 8 Microstructures of friction welded joints. The friction time: 2 sec.

4 Fig. 9 Hardness distribution of friction welded joints. The friction time: 2 sec. Fig. 10 Results of Charpy impact tests. The friction time: 2 sec.

$Fig. 11 Macrofractographs of Charpy impact fractured specimens. The friction time: 2 sec. Fig.$

5 Fig. 11 Macrofractographs of Charpy impact fractured specimens. The friction time: 2 sec. Fig. 12 Microfractographs of Charpy impact fractured specimens. The friction time: 2 sec. Fig. 13 S-N curves of base metals and friction welded joints. The friction time: 2 sec.

$Fig. 14 Macrofractographs of fatigue fractured surfaces. The friction time: 2 sec. Fig. 16 Microfractographs of stage II on the fatigue fractured surfaces. The friction time: 2 sec. Fig. 17 Microfractographs of final stage on the fatigue fractured surfaces.$

6 Fig. 14 Macrofractographs of fatigue fractured surfaces. The friction time: 2 sec. Fig. 16 Microfractographs of stage II on the fatigue fractured surfaces. The friction time: 2 sec. Fig. 17 Microfractographs of final stage on the fatigue fractured surfaces. The friction time: 2 sec. Fig. 15 Microfractographs of stage I on the fatigue fractured surfaces. The friction time: 2 sec.

7 5) V. M. Plyatski: "Shtampovka lz Zhidkogo Metalla" (Moscow, 1964), R "Extrution Casting", (Primary Sources, New York, 1965), 10.

Continuous Cooling Transformation Diagrams for Welding of Mn-Si Type 2H Steels. Harujiro Sekiguchi and Michio Inagaki Synopsis: The authors performed

Continuous Cooling Transformation Diagrams for Welding of Mn-Si Type 2H Steels. Harujiro Sekiguchi and Michio Inagaki Synopsis: The authors performed a series of researches on continuous cooling transformation