预备热处理对TB2淬火组织影响研究

Study on the Effect of Preheat Treatment on Quenched Structure of TB2

对A、B、C、D四组TB2热态试样坯分别进行800℃/0.5h.WC+650℃/4h炉冷至550℃.AC、800℃/0.5h.WC+650℃/1h炉冷至550℃.AC、800℃/0.5h.AC+650℃/1h炉冷至550℃.AC和650℃/1h炉冷至550℃.AC的热处理,然后在735℃~750℃温度范围内淬火。采用光学显微镜观察了试样淬火前和淬火后的显微组织,重点研究TB2合金淬火组织中α→β相的转变规律。结果表明,4组试样经预备热处理后,显微组织中都有一定量的α相析出;观察随后的淬火组织发现,在735℃和740℃较低温度下淬火,A组和B组试样淬火组织中β晶界和晶粒内部都有大量的α相析出,而C组和D组试样中α相则主要分布在晶界,晶内含量极少;不管采用哪种预备热处理工艺,淬火组织都遵循相似的演变规律,随着淬火温度的升高,组织中α相逐渐减少,首先在晶界消失,直至750℃时,晶内α相也完全消失,4组试样均完成了α→β相转变;尽管A、B、C、D,4组试样的淬火组织有所不同,但并不改变TB2合金α→β的相转变温度。若实际生产中需要测试该类亚稳β钛合金相转变温度时,可以根据实际情况选择合适的预备热处理工艺。

The four groups of TB2 hot-state sample blanks A,B,C,and D were respectively heat treated by heating at 800℃for half an hour and water cooling,then heating at 650℃for 4h,furnace cooling to 550℃and air cooling,and heating at 800℃for half an hour and water cooling,then heating at 650℃for 1h,furnace cooling to 550℃and air cooling,and heating at 800℃for half an hour and air cooling,then heating at 650℃for 1h,furnace cooling to 550℃and air cooling,and heating at 650℃for 4h,furnace cooling to 550℃and air cooling,then quenched in the range of 735℃to 750℃.The microstructure of the samples before and after quenched was observed by optical microscope,and it was mainly studied that the evolution of phase transformation ofαintoβin the quenched structure of TB2 alloy.The results show that a certain amount ofαphase are precipitated in structure of the four groups of samples after preparatory heat treatment;observation of the subsequent quenching structure shows that there is a large amount ofαphase precipitation at theβgrain boundary and inside the grain in the quenched structure for the samples in group A and group B quenched at lower temperatures of 735℃and 740℃.while theαphase in group C and group D samples is mainly distributed in the grain boundary,and only a few are inside the grain;No matter which preparatory heat treatment process is used,all the quenched structure follows a similar evolution.With the increase of the quenching temperature,theαphase gradually decreases,and first disappears at the grain boundary,until 750℃,the intragranularαphase also completely disappears,and all four groups of samples complete the transformation ofαintoβ;Although the quenched structure of the four groups of samples A,B,C,and D are not exactly the same,they do not changeβphase inversion temperature of the alloy.If the phase transition temperature of this type of metastable beta titanium alloy needs to be tested in production,a suitable preparatory heat treatment process can be selected according to the actual situation.