热挤压钛/钢复合管的微观组织和性能

Microstructure and Property of Ti/Steel Composite Pipe Prepared by Hot Extrusion

以低碳钢Q235为内管、以工业纯钛TA2为复管,用热挤压工艺制备了钛/钢复合管,使用金相显微镜、场发射扫描电子显微镜、X射线衍射仪、显微硬度仪和纳米压痕等手段对其表征,研究了这种钛/钢复合管的力学性能与结合界面微观组织的关系。结果表明,钛/钢复合管的外径为22 mm,内外壁厚分别为2.8 mm和0.4 mm,复合界面结合良好,界面内的主要物相为α-Fe、α-Ti、TiC及Fe_(2)Ti;高温挤压使钛/钢复合管结合界面处的位错密度提高和晶粒明显细化,复合管钛侧的晶粒细化程度比基材钢侧的高,界面晶粒的平均尺寸为1.5μm。加工硬化和高温热挤压使钛/钢结合界面的硬度提高,界面结合处的硬度最大。低温退火削弱了钛/钢复合管的加工硬化程度,提高了界面材料的刚度,而对界面金属间化合物生成的反应层的影响较小。

The titanium/steel composite pipe was prepared by hot extrusion at 1000℃with low carbon steel Q235 as inner pipe and commercial pure titanium TA2 as cladding.The effect of interface microstructure on mechanical properties of titanium/steel composite pipe was studied by using metallographic microscope,field emission scanning electron microscope,X-ray diffractometer,microhardness tester and nano-indentation technology.The results show that the outer diameter of the extruded titanium/steel composite pipe is 22 mm,the inner and outer wall thicknesses are 3 mm and 0.2 mm respectively,the interface of steel/Ti pipes is well bonded,and the main phase of the interface isα-Fe,α-Ti,TiC and Fe_(2)Ti,etc.The grain at the interface junction of the hot extruded Ti clad steel pipe is obviously refined,and the average grain size of the interface is 1.5μm.The grain refinement of the Ti side of the composite is higher than that of the steel side.At the same time,under high temperature hot extrusion,the dislocation density at the bonding interface of the clad pipe increases,the grains are refined,and the microhardness is also improved.Low temperature annealing has different effects on the mechanical properties of both sides of titanium/steel composite interface,weakens the work hardening degree of titanium/steel composite pipe,improves the stiffness of interface material,and has little effect on the reaction layer formed by interface intermetallic compound.