Abstract: In order to explore the free cutting direction and critical cutting depth of single crystal gallium oxide crystal ultra-precision machining，the (100) crystal plane and (010) crystal plane of the single crystal gallium oxide was divided into 24 equal parts at equal angles, and nanoindentation tests with Berkovich diamond indenter were conducted, nanoindentation scratch with Cube diamond indenter tests were conducted. The critical depth of cut for brittle-plastic transformation is the largest at 120° of the (100) crystal plane, which is about 623 nm, and the critical load of brittle-plastic transformation is 29.4 mN. The critical depth of cut for brittle-plastic transformation is the cargest at 105° of the(010) crystal plane, which is about 686nm, and the critical load of brittle-plastic transition is 20.0 mN. Gallium oxide crystals have strong anisotropy, and the (010) plane anisotropy is relatively strong. Comparing the variation trends of hardness, elastic modulus, fracture toughness and relative brittle-plastic transition critical depth of cut with direction, combined with the scratch test results in various directions, it may be seen that the (010) plane of gallium oxide crystal is an easy-to-process crystal plane, and the 105° direction is the easy machining direction.

Key words: gallium oxide crystal, anisotropy, mechanics property, brittle-plastic transition

摘要： 为了探寻单晶氧化镓晶体超精密加工的易切削方向以及临界切削深度，将单晶氧化镓晶体(100)晶面和(010)晶面等角度划分成24等份，对每个方向上用Berkovich金刚石压头进行纳米压痕试验、用Cube金刚石压头进行纳米压痕和划痕试验。试验结果表明，在(100)晶面120°方向上脆塑转变临界切深最大，为623 nm左右，此时脆塑转变临界载荷为29.4 mN；在(010)晶面105°方向上脆塑转变临界切深最大，为686 nm左右，此时脆塑转变临界载荷为20.0 mN。氧化镓晶体存在强烈的各向异性，其中(010)面各向异性较为强烈。对比硬度、弹性模量、断裂韧度和相对脆塑转变临界切深随方向的变化趋势，结合各方向的划痕试验结果可以看出，氧化镓晶体(010)面为易加工晶面，105°方向为易加工方向。

关键词: 氧化镓晶体, 各向异性, 机械性能, 脆塑性转变