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首页> 外文期刊>Materials Science and Engineering >Hot tensile and stress rupture behavior of friction welded alloy 718 in different pre-and post-weld heat treatment conditions
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Hot tensile and stress rupture behavior of friction welded alloy 718 in different pre-and post-weld heat treatment conditions

机译：摩擦焊接合金718在不同焊前和焊后热处理条件下的热拉伸和应力断裂行为

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摘要

Alloy 718 rods in two different heat treated conditions (solution treatment (ST) and ST followed by aging (STA)) were friction welded. The weld joints were subjected to two different post-weld heat treatments (direct aging (DA) and STA). Tensile tests were carried out at 650 ℃ with an initial strain rate of 10~(-4) s~(-1). Stress rupture tests were performed at 650 ℃ at a constant load with an initial stress level of 690 MPa. The ultimate tensile strength values for all conditions, expect for base material in ST condition and weld joints with prior ST or STA in the as-welded condition, were higher than the minimum value of 1000 MPa specified by the Aerospace Material Specification for the base material in STA condition. The weld joint specimen in the as-welded state with prior STA condition failed in heat affected zone (HAZ). Though strengthening precipitates (γ″) dissolved in weld metal and HAZ during welding, HAZ was weaker than weld metal due to coarser grains and so failure occurred in HAZ. In all other conditions, samples failed in base metal. The stress rupture properties such as minimum creep rate and time to rupture of the base material in ST condition and as-welded joints with prior ST or STA condition are almost same. The sample subjected to STA both before and after welding exhibits the best stress rupture properties. It may be attributed to homogenization as well as moderate coarsening of grain structure of weld zone and fine and uniform distribution of strengthening precipitates throughout the weldment. However, to obtain the best combination of tensile and stress rupture properties, the material should be welded in ST condition and it should be subjected to direct aging after welding.
机译：在两种不同的热处理条件下（固溶处理（ST）和ST，然后进行时效处理（STA））对718合金棒进行摩擦焊接。对焊缝进行两种不同的焊后热处理（直接时效（DA）和STA）。在650℃下进行拉伸试验，初始应变率为10〜（-4）s〜（-1）。在650℃的恒定载荷下进行应力断裂试验，初始应力水平为690 MPa。在所有条件下的极限抗拉强度值，预期在ST条件下的基础材料以及焊接状态下具有先前ST或STA的焊接接头，均高于航空航天材料规范为基础材料指定的最小值1000 MPa在STA条件下。焊接状态的样品在焊接前状态为STA之前在热影响区（HAZ）中失效。尽管在焊接过程中焊缝金属和热影响区中溶解有强化析出物（γ''），但由于晶粒较大，热影响区比焊缝金属弱，因此在热影响区发生了故障。在所有其他条件下，样品的贱金属均不合格。应力断裂特性，如最小蠕变速率和在ST条件下的基体材料断裂时间以及在先有ST或STA条件下的焊后接头几乎相同。在焊接之前和之后进行STA腐蚀的样品均表现出最佳的应力断裂性能。这可能归因于焊缝区晶粒组织的均质化和适度粗化以及整个焊缝中强化沉淀物的精细均匀分布。但是，为了获得拉伸和应力断裂性能的最佳组合，应在ST条件下焊接该材料，并在焊接后对其进行直接时效处理。

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