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首页> 外文期刊>Materials Science and Engineering >The microstructure and impression creep behavior of cast, Mg-5Sn-xCa alloys
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The microstructure and impression creep behavior of cast, Mg-5Sn-xCa alloys

机译：Mg-5Sn-xCa铸造合金的显微组织和压痕蠕变行为

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摘要

The effects of 0.7,1.4 and 2 wt.% Ca additions on the microstructure and creep behavior of a cast Mg-5Sn alloy were investigated by impression tests. Impression creep tests were carried out in the temperature range 423-523 K and under punching stresses in the range 150-475 MPa for dwell times up to 3600 s. Analysis of the data showed that for all loads and temperatures, the Mg-5Sn-2Ca alloy had the lowest creep rates, and thus the highest creep resistance among all materials tested. This is attributed to the diminishing of the less stable Mg_2Sn particles and formation of the more thermally stable CaMgSn phase which strengthens both matrix and grain boundaries during creep deformation in the investigated system. The creep behavior can be divided into two stress regimes, with a change from the low-stress regime to the high-stress regime occurring, depending on the test temperature, around 0.012 < (σ_(imp)/G) < 0.024. Based on the steady-state power-law creep relationship, the stress exponents of about 5-6 and 10-12 were obtained at low and high stresses, respectively. The low-stress regime activation energies of about 97 kJ/mole, which are close to that for dislocation-pipe diffusion in the Mg, and stress exponents in the range 5-6 suggest that the operative creep mechanism is dislocation viscous glide. This behavior is in contrast to the high-stress regime, in which the stress exponents of 10-12 and activation energies of about 163 kJ/mole are indicative of a dislocation climb mechanism with back stress similar to those noted in dispersion strengthening.
机译：通过压痕试验研究了添加0.7、1.4和2 wt。％的Ca对铸造Mg-5Sn合金的组织和蠕变行为的影响。在423-523 K的温度范围内，在150-475 MPa的冲压应力下进行了3600 s的保压时间下的蠕变试验。数据分析表明，对于所有负载和温度，Mg-5Sn-2Ca合金的蠕变速率最低，因此在所有测试材料中具有最高的抗蠕变性。这归因于不稳定的Mg_2Sn颗粒的减少和热稳定的CaMgSn相的形成，该相在研究系统的蠕变变形过程中加强了基体和晶界。蠕变行为可以分为两个应力状态，根据测试温度，从低应力状态到高应力状态会发生变化，大约为0.012 <（σ_（imp）/ G）<0.024。基于稳态幂律蠕变关系，在低应力和高应力下分别获得约5-6和10-12的应力指数。大约97 kJ / mol的低应力状态活化能，接近于位错管在Mg中的扩散能量，应力指数在5-6范围内，表明有效蠕变机理是位错粘性滑移。此行为与高应力状态相反，在高应力状态中，应力指数为10-12，活化能约为163 kJ / mol，表明位错爬升机制的背应力类似于分散强化中提到的那些。

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