Shape Memory Effect of As-aged Fe-14Mn-5Si-8Cr-4Ni-0.2C Alloy

The effects of aging temperature on shape memory effect, mechanical properties and microstruc-ture of Fe-14Mn-5Si-8Cr-4Ni-0.2C shape memory alloy have been studied. The results showed that the second phase particles rich in chromium, manganese and silicon precipitate during aging, and thereby increase the hardness and strength of the alloy. The shape recovery ratio can be remarkably improved by aging and a maximum value can be obtained at 1223 K, which is 68% higher than that of the specimen in solid solution state. When the aging temperature is below 1223 K, the amount of second phase particles increases as the aging temperature increases. The size of austenite grain increases with increasing aging temperature. When the temperature is over 1223 K, the second phase particles can not precipitate. The lack of second phase particles and the increase of grain size make the hardness and shape recovery ratio drastically decrease, when the temperature is over 1223 K.

热-机械循环训练对Fe-15Mn-4Si-8Cr-4Ni形状记忆合金耐腐蚀性能和低温应力松弛的影响

研究了热-机械循环训练对Fe-15Mn-4Si-8Cr-4Ni形状记忆合金耐腐蚀性能以及低温松弛的影响,结果表明,随着循环次数的增加,合金在5%NaOH溶液中的耐腐蚀性能呈下降的趋势,这是因为热-机械循环处理导致了碳化物的大量析出,从而降低合金的耐腐蚀性能;经过热-机械循环处理后合金的低温应力松弛率高于未经循环处理的合金,约提高3%左右。导致合金低温应力松弛率提高的原因是回复应力的提高为应力诱发ε马氏体相变提供了大的机械驱动力以及应力诱发ε马氏体的临界应力的降低。