Desired grain flow
Desired grain flow
(OP)
say a forging, produces a desired grain flow.
annealing will not affect that grain flow, right? and keep the benefit of the grain flow, right?
only solution heat treatment will remove the grain flow, right?
thanks.
annealing will not affect that grain flow, right? and keep the benefit of the grain flow, right?
only solution heat treatment will remove the grain flow, right?
thanks.





RE: Desired grain flow
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P.E. Metallurgy, Plymouth Tube
RE: Desired grain flow
RE: Desired grain flow
In many cases you are also concerned about formation of secondary phases.
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P.E. Metallurgy, Plymouth Tube
RE: Desired grain flow
let's pick a particular material. 6061 aluminum.
let's say, the T6 condition 6061 can be thread rolled. the benefit of the rolling increases the fatigue strength of this bolt. if this bolt is subsequently subjected to high temperature, its strength will be reduced. at what temperature, the benefit of the thread rolling will be gone?
RE: Desired grain flow
Also MMPDS-10 (formerly MIL-HDBK-5) has many graphical illustrations addressing mechanical properties vs temperature.
RE: Desired grain flow
RE: Desired grain flow
Many age hardenable alloys are thread rolled, right before the final aging.
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P.E. Metallurgy, Plymouth Tube
RE: Desired grain flow
As part of the EUCAR Mg-Engine project involving Opel, Renault, Volvo, BMW and various suppliers and universities, aluminium bolts were evaluated for fatigue strength vs. temperature. Two conditions were evaluated: threads rolled after T6 heat treatment (FTR) and threads rolled before T6 heat treatment (FHT). The results were plotted as fatigue strength vs. test temperature. Fatigue strength continuously decreased from room temperature up to the maximum that was evaluated (150 °C). A 2nd order polynomial equation was fit to the data:
> Bolts M10 FHT: y = -0,0005x2 - 0,0299x + 29,309
> Bolts M10 FTR: y = 0,0004x2 - 0,1635x + 41,171
y axis = stress amplitude (σa50% in MPa), x-axis temperature in C
For FTR condition, stress amplitude at room temp was 38 MPa, decreased to 31 MPa at 80 °C, 27 MPa at 120 °C, and 26 MPa at 150 °C. The following is an excerpt regarding long term aging:
Ageing (2,200h/+150°C) of the bolts M10 with final thread rolling production sequence (FTR) also reduces the fatigue strength significantly from σa50% = 38 N/mm2 to σa50% = 30 N/mm2. This equals to a drop of -21%.
This result can be explained by residual stresses induced in the thread root by the workhardening effect of the final thread rolling process. The induced residual stresses increase the fatigue strength of the aluminium bolts. This effect is also known with steel bolts. The ageing at +150°C causes a reduction of the residual stresses which in consequence leads to a drop of the fatigue strength.
Source: Mg-Engine-TR-D9b-2006
Author: Th. Marx, Adam Opel GmbH, Rüsselsheim/Germany