TiAl基合金低温超塑性变形的力学行为

中国有色金属学报, 2003, 13(2): 442-447.

TiAl基合金低温超塑性变形的力学行为

张俊红 ^1, , 黄伯云 ^2, , 贺跃辉 ^3, , 孟力平 ^4,

1.中南大学,粉末冶金国家重点实验室,长沙,410083;郑州轻金属研究院,郑州,450041

2.中南大学,粉末冶金国家重点实验室,长沙,410083

3.中南大学,粉末冶金国家重点实验室,长沙,410083

4.中南大学,材料科学与工程学院,长沙,410083

基金项目: 国家高技术研究发展计划(863计划)(715-005-0040)

关键词： TiAl基合金 , 超塑性 , 速率控制机制

Mechanical behaviors of TiAl alloy during low temperature superplastic deformation

采用恒应变速率和应变速率递增实验研究了Ti-48Al-2Cr-0.2Mo(摩尔分数,%)合金在常压空气中的低温超塑性变形力学行为,并且探讨了TiAl基合金的低温超塑性变形机理.研究结果表明,TiAl基合金的变形组织具有良好的空气中低温超塑性变形性能.在t=900 ℃,ε*=5×10-4s-1时,伸长量δ达到最大值为413%,即使在较低的温度(t=800 ℃)和较高的应变速率(ε*=1×10-3s-1)下变形,伸长量δ值仍然超过300%.在整个变形区间m值均大于0.3,mmax为0.78.当t＞900 ℃或ε*＜5×10-4s-1时,剧烈氧化导致超塑性变形性能的恶化和脆性断裂.在900～950 ℃之间,TiAl基合金超塑性变形的热激活机制发生转变.实验测得TiAl基合金在800～900 ℃ 时超塑性变形的热激活能为Qav=178 kJ/mol,这个数值介于γ-TiAl的蠕变体积激活能和TiAl基合金的空位迁移能之间,而接近于后者,因此,TiAl基合金低温超塑性变形的速率控制机制是晶界扩散.

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