Abstract

In this study, the creep responses of two near-eutectic Al-Si-Cu-Mn alloys, Al-12wt pctSi-4 pctCu-1.2wt pctMn alloy (Alloy-1, containing dendritic Mn-rich primary phase) and Al-12wt pctSi-4 pctCu-2wt pctMn-1wt pctCr alloy (Alloy-2, containing star-like Cr-Mn rich primary phase), were investigated from 448 K to 523 K at 40 to 70 MPa applied stress. Results show that with 100 hours of exposure at 448 K/40 to 70 MPa, true steady-state creep was not attained. However, at 473 to 523 K/40 to 70 MPa, both the alloys showed a fixed creep rate establishing steady-state creep. The creep curves of the studied alloys illustrate that Alloy-1 exhibits lower creep rates and less creep strains than Alloy-2 in each combination of temperature and applied stress. Considering the creep rates and total creep strains after 100 hours of exposure, Alloy-1 possesses much better creep resistance than Alloy-2, even though the high-temperature strength of Alloy-2 is higher than that of Alloy-1 at 448 K and 523 K. Higher strength at high temperatures does not mean high creep resistance at high temperatures. At low to moderately high temperatures (0.48 to 0.53 T_m where T_m is the equilibrium melting point of pure Al in K) and applied stress of 40 to 70 MPa, the creep mechanisms in Alloy-1 and Alloy-2 are similar and diffusion is the rate-controlling process.

中文翻译：

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两种含有枝状富锰基相或改性的类似铬锰富集相的近共晶Al-Si-Cu-Mn耐热合金的蠕变行为

摘要

在这项研究中，两种接近共晶的Al-Si-Cu-Mn合金的蠕变响应，即Al-12wt pctSi-4 pctCu-1.2wt pctMn合金（Alloy-1，含有树枝状富锰初生相）和Al-12wt研究了pctSi-4 pctCu-2wt pctMn-1wt pctCr合金（合金2，含有富含Cr-Mn的星形初级相）在40至70 MPa的施加应力下从448 K至523 K的情况。结果表明，在448 K / 40到70 MPa的压力下暴露100小时，无法获得真正的稳态蠕变。然而，在473至523 K / 40至70 MPa时，两种合金均显示出固定的蠕变速率，从而建立了稳态蠕变。所研究合金的蠕变曲线表明，在温度和外加应力的每种组合下，合金1的蠕变速率和蠕变应变均比合金2低。考虑到暴露100小时后的蠕变速率和总蠕变应变，即使在448 K和523 K时，合金2的高温强度比合金1的高温强度高，合金1的抗蠕变性也比合金2更好。在高温下更高的强度并不意味着具有较高的抗蠕变性在高温下。在低温到中等高温（0.48至0.53T _m，其中T _m是纯Al在K中的平衡熔点）和40至70 MPa的外加应力，合金1和合金2的蠕变机理相似，扩散是速率控制过程。