采用电子探针、透射电镜和X射线衍射方法研究了添加微量B元素(0~1%)(质量分数)对Ni-46Ti-4Al合金微观组织的影响,并采用力学压缩试验测试了合金的室温和高温力学性能.结果表明,Ni-46Ti-4Al合金由NiTi基体和(Ti,Al)<,2>Ni两相组成.添加微量B元素(0.02%)可以促使Ni-46Ti-4Al合金中出现TiB<,2>化合物,且与(Ti,Al)<,2>Ni相都在晶界上析出.随着B含量增加,(Ti,Al)<,2>Ni相逐渐减少,TiB<,2>相逐渐增多.这两相的硬度均高于NiTi基体相,是合金中的强化相.添加适量的B可以显著提高Ni-46Ti-4Al合金的室温和高温屈服强度,例如:添加l%B合金的室温屈服强度达到2553 MPa,比Ni-46Ti-4Al合金提高了128%.添加0.02%B和1%B合金在600℃时的屈服强度分别为382和498 MPa,比Ni-46Ti-4Al合金提高了35%和70%.合金屈服强度和两个强化相((Ti,Al)<,2>Ni和TiB<,2>相)的总体积分数成正比.B加入后一方面使Ni-46Ti-4Al合金得到固溶强化,另一方面,还促使生成具有强化作用的TiB<,2>相,这是合金室温和高温屈服强度提高的主要原因.
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