時効性アルミニウム鋳物合金の疲れ強さにおよぼすピーニング加工の影響

概要

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An age-hardening type Auminium casting alloy (JIS AC8A Lo-Ex) was aged after the solution treatment, and given a peening or a liquid honing treatnient. Then the effect of a peening on the fatigue strengths of such treated specirmns was examined. The results obtained were as follows:　(1) In order to improve the fatigue strength of this material, the peening and the liquid honing after T_7 treatment, i.e. solution treatment followed by ageing for 8 hours at 225+-5℃ are very effective. The fatigue strength of the shot-peened specimem was increased by about 30% as compared with the not-treated one, and that of the liquid-honed specimen, by about 25%.　(2) The increase of the fatigue strength may be greatly affected by the residual stress in the surface layer of the specimen.　(3) From the decrease of the hardness near the fatigue fracture, it is found that the residual compressive stress caused by the peening is reduced as the specimen fatigues, and that the age-hardening is also reduced as if the over-ageing occurs.　(4) An increase in fatigue life can be caused by the age-hardening and the residual compressive stress.
1974-02-20