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Volume 36, Issue 4
Displaying 1-9 of 9 articles from this issue
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Kentaro TANIUCHI1986 Volume 36 Issue 4 Pages 189-190
Published: April 30, 1986
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (322K) -
Seiichi ANDO, Michinori OHKUBO, Junichi KANEKO1986 Volume 36 Issue 4 Pages 191-199
Published: April 30, 1986
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESS7050 aluminum alloy extruded plates 12mm in thickness were electron beam welded. Effects of Zr up to 0.16% in the base metal on the microstructures and mechanical properties of welds were investigated. Tensile strength, ductility and fatigue strength of the welded joints naturally aged after welding are affected by Zr contents. The welds of Zr added base metal show higher tensile strength and elongation than those of Zr free one owing to refined grain size in the fusion zone. The properties of welded joints T7-tempered after welding are, however, above 90% irrespective of Zr contents. Nevertheless, T7-tempered welds show considerably lower ductility and impact absorbed energy than the base metal. The optimum Zr content 0.12% in the base metal is recommended.View full abstractDownload PDF (1942K) -
Kenji HIGASHI, Yasushi HIRAI, Tadakazu OHNISHI1986 Volume 36 Issue 4 Pages 200-206
Published: April 30, 1986
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe dependence of strength and toughness on temperatures was investigated for under- (UT), peak- (T6) and over-aged (T7) 7075 alloys. These alloys have excellent static tensile properties and show appreciable low temperature embrittlement. Critical crack tip opening displacement (CTODc) derived from the stretched zone analysis significantly depends on temperature and aging condition. The alloy peak-aged shows the greatest degree of embrittlement and one under-aged does lesser degree than one over-aged. The generation of laminated fracture at low temperatures is accelerated as CTODc reduces. It depends on the microstructure more strongly than the degree of embrittlement. Under the same level in fracture toughness, the area of laminated fracture is smaller in over-aged peak-aged and underaged, alloys in due order. A decrease in CTODc at low temperatures is attributed to the ease of nucleation of microvoids at smaller size of second particles both by an increase in yield strength and localization in strain ahead of stretched zone. This means a numerical increase of second particles which is effective to determine the order of stretched zone and decreases both in inclusion spacing and dimple size.View full abstractDownload PDF (1620K) -
Tsuneo TAKAHASHI, Tatsuo SATO1986 Volume 36 Issue 4 Pages 207-214
Published: April 30, 1986
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSPrecipitation phenomena and structural changes in Al-2.15mass%Li and Al-2.70mass%Li alloys were investigated respectively by hardness measurements, specific heat measurements and electron microscopy.
Hardness increases slowly with aging time at room temperature and 323K, while increases remarkably at 373-473K in the both alloys. At 523K, no increase in hardness occurs in an Al-2.15mass%Li alloy, but rapid increase occurs initially in an Al-2.70mass%Li alloy. Various reactions of heat evolution and absorption were observed in the specific heat curves depending on aging temperatures and times. Furthermore, TEM observations suggest that the L12 ordered structure δ', which exists even in the as-quenched state, is completely coherent with the matrix initially and loses the coherency subsequently to become semi-coherent. The precipitation sequence in an Al-Li binary alloy was found to be as follows:
α→Li cluster (GP(1))→Short range order(GP(2))→L12 ordered
structure(δ': coherent→semi-coherent)→Stable phase(δ)View full abstractDownload PDF (2378K) -
Mitsuo NIINOMI, Makoto ADACHI, Toshiro KOBAYASHI1986 Volume 36 Issue 4 Pages 215-222
Published: April 30, 1986
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDirect current electrical potential method, instrumented Charpy impact test, key curve method, compliance changing rate method, fractography or NRL type dynamic tear test are carried out for the evaluation of static and dynamic crack initiation resistance toughness (JId, JIC) and crack propagation resistance toughness (JR curve, Tmat).
The static JR curve and Tmat shows plate thickness dependency; the crack propagation resistance toughness is larger as plate thickness is smaller. The dynamic Tmat shows strain rate dependency. Each method is proved to be sufficiently effective for the toughness evaluation of the aircraft material; 7075 (Al-Zn-Mg-Cu type) alloy.View full abstractDownload PDF (943K) -
Yutaka KATO, Eizo ISOYAMA, Toshimitsu UCHIYAMA, Takashi MOMOSE, Hajime ...1986 Volume 36 Issue 4 Pages 223-229
Published: April 30, 1986
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe purpose of this experiment was to improve the limit of determination of hydrogen in aluminum. As variation of surface gases on samples affected the limit of determination in an usual analytical method (a method of determing internal hydrogen by correcting surface hydrogen), a way of removing surface gases by discharge cleaning prior to analysis was studied in the present work. The results were as follows;
1) Aluminum surface gases consisted of mainly H2, H2O, CO, and CO2.
In those gases, H2 and CO were remarkably detected.
2) Those surface gases could be removed by He discharge cleaning.
CO as surface gas was 1×10-5torr.l (3.5×1013molec./cm2) after discharge cleaning, and was about 1×10-3 torr.l(3.5×1015molec./cm2) with no discharge cleaning.
3) Analyzing aluminum sample which contained internal hydrogen of 0.11cc/100g Al after discharge cleaning, all internal hydrogen measured by an usual analytical method.
Improvement of the limit of determination of internal hydrogen by discharge cleaning is considered to be possible.View full abstractDownload PDF (900K) -
Takeshi MURAKAMI, Tsuneo TAKAHASHI1986 Volume 36 Issue 4 Pages 230-234
Published: April 30, 1986
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSPolycrystalline pure aluminum was rolled to low reduction below 50 per cent and annealed at 400 or 500°C. The orientations of grains with straight edge boundaries were determined by micro Laue technique with collimator of 100μm diameter. Twin orientation, coincidence boundary of ∑3, was detected when grain diameters were larger than around 100μm.
Dependence of formation of straight-edge boundary on rolling reduction and rolling temperature was also investigated. Wedge type specimen was rolled through one draft at room and liquid nitrogen temperature and annealed. Straight edge boundaries were identified as twin interfaces because those traces are parallel to slip traces. Straight-edge boundaries were observed more frequently when rolling temperature was liquid nitrogen temperature than room temperature.View full abstractDownload PDF (1277K) -
Hiroyuki YOSHIDA1986 Volume 36 Issue 4 Pages 235-246
Published: April 30, 1986
Released on J-STAGE: July 23, 2008
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Hiroshi TANAKA1986 Volume 36 Issue 4 Pages 247-252
Published: April 30, 1986
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (958K)
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